View Full Version : Continuing power drop off issues....
Way back when I first got my truck over a year and a half ago, I took my Wife's Fullsize Blazer for a ride on my car trailer to aid in break-in.
While on the highway at about 55 or so, going up a hill, I lost power for a bit. I manually downshifted it to 3rd and it came back to life.
The truck was 100% stock at the time.
Now after 38,000 miles, different tires, propane, airbox mods, and all updates, I still experience the same problem every once in a while.
All summer the truck has been doing great except every so often I could make it drop off and almost stall at highway speed once in a while if I get on it at around 70mph for a little. Kinda like running out of fuel for about 15 - 20 seconds. By just feathering for a while or sometimes manually dropping down a gear, she comes back to life.
I also have noticed since the weather has cooled down it is more suseptable to that condition and going into limp with propane on.
I've had all the updates done during the summer so they haven't fixed the issues.
I have no idea what's going on. If I run without propane, it seems fine. Cold morning with propane, forget it.
Sometimes even with propane off it will do the highway power down as described earlier.
I have a strange feeling something just isn't right with a sensor somewhere, wether it be in the Allison or the engine. Why does it power down?
I do get the SES light sometimes with the power down and always if she goes limp. Limp is easy to detect cause it's feels like the tranny simply jumps out of gear and the SES comes on immeadiately. I then have to pull over, stop, shut it down, restart and she's back.
Now this may be two seperate issues. One simply being Ally slip. The other (power down) is something else cause it's not always during a high load situation.
My estimated RWHP with lp is around 325. From reading many posts, this should be below Ally slip numbers??
Maybe time for a service call....
[ 11-04-2002: Message edited by: hoot ]</p>
Hoot
It doesn't downshift??? I can get mine to downshift at higher speeds 70+(Drop Out Of OD) and really not gain anything out of it,kinda just hangs there unless I let up.....But if I roll it out different story.....Straight to limiter....
I can understand the propane mourning thing prolly the cold ally isn't ready.....
It will be interesting to hear what happens...Definately gonna be one of them you going to have to bring service manager for a ride....Have fun explaining the extra LP..... :eek:
MAC
[ 11-04-2002: Message edited by: mackin ]</p>
No MAC, it's definately a power drop off. Like it's intentional. I still feel some power but barely enough to keep up highway speed. Kinda coasting for 10 seconds or so till it decides it's ok to continue.
I just got back from a run tonight to Lancaster, Pa. by way of Bird in Hand, Intercourse and Paradise. (These are real towns). About 50 miles each way. No problems at all.
Yea the morning thing I understand. I need to leave well alone and run stock in the morning.
The only thing here that bothers me is the power down. I might go weeks without it happening but I can usually make it happen.
Not sure how I'm gonna handle it. If I was hauling and it happened I would be po'd. Could be dangerous.
SoCalDMAX
11-05-2002, 09:24
Hoot,
I'm no expert. At first I thought you were talking about limp mode. Then I realized it was 2 different phenomena. As for your propane power estimate, I would guess you're putting down AT LEAST 345rwhp. Probably more as the air gets colder and denser. Mine makes 345 at 70* ambient and it's a "Mackin loves them tree-huggers special". ;)
I don't know exactly how the Dmax uses the MAF; if it's a closed loop system like gassers then it's adding more fuel to go with the denser air. Add the catalytic power of the propane and the numbers are sure to go up.
I'm guessing the limp mode issue is just a case of more power than the Ally can take going into 5th. Given production tolerances, you may well be making 125 or more extra hp at the crank and your Ally might be a little touchy.
IRT the power down issue, I'm thinking you're right, it might be a defective and/or intermittent sensor. These things have more sensors than bolts nowadays.... Maybe if you sweet talked the dealer into having the tech ride with you w/the Tech II hooked up and see if he can capture the event...
How old is the fuel filter? Maybe you just ercently got a tank of bad fuel? Or it might be Duke playing around and putting a little gas in your tank periodically... :eek:
Good luck! Steve
Duke is a jewel. He's over at ThedieselStop (FD.com) using my name in vain as we speak. It's all in fun.
I always keep a clean fuel filter. This truck has had this quirk since day one.
You're right. I need to get a tech to go for a ride with me. I was hoping others have experienced the same power-downs as me.
You are also right about the cooler weather. Man it makes a huge difference in power on cool mornings with lp on. I leave it off now at least for 10 miles or so.
[ 11-05-2002: Message edited by: hoot ]</p>
Are you sure the ECM software updates were done? That would be the FIRST thing that I would do. MANY updates for false trouble codes along the way! Knowing what codes are set would also help.
[ 11-05-2002: Message edited by: kennedy ]</p>
SoCalDMAX
11-05-2002, 10:46
You know, the funny thing about Duke is, despite his protestations, it appears he spends a lot of time quoting you... ;)
It must actually be quite flattering. :D
Regards, Steve
John,
As far as the updates being done...
The place I took it to is very compitent. The cold lope got better and the cruise control now flutters the speed within 2 mph. That's a bit annoying. 65, 67,65,67. Shifting is better. Truck runs great but that power down is still there.
The SES never stays on very long. Maybe an hour then it's gone. And it doesn't always come on on the power-downs.
John, do you notice cold weather performance changes? With torch? More sensitive Ally?
CntrlCalDmax
11-05-2002, 12:57
hoot,
Mine has done the same thing towing with the juice on level 2. The first time I pulled over and let it idle for a few. Took off again and all was fine. The next time it happened, I tried more power and all it would do is downshift. I feathered the power and in about 15 seconds it ran fine. The SES light came on but not at the same time, it was a few hundred miles later. Codes P0101 and P0236. Light went out in a couple of hundred miles. Each time it happened I was towing up a hill. Finally my co-pilot was worried about loosing power at the wrong time and made me remove the juice. It didn't happen the rest of the 7,000 mile trip. I thought the TCM was trying to protect the Alli, but, if you have the 6 speed then......?
Leo
I reread your first post and see that you have the allison. Could the TCM have that kind of control over the engine to protect the tranny?
[ 11-05-2002: Message edited by: CntrlCalDmax ]</p>
CntrlCalDmax,
Sounds similar.
Maybe what I'm experiencing is the same thing you Juicers are experiencing.
Maybe there is nothing wrong with the Juice programming. It's the ECM/TCM doing the dirty deeds.
But...... mine has done it bone stock.
CntrlCalDmax
11-05-2002, 13:50
When it has done it bone stock, were you pulling a lot of power? Do you remember what gear it was in? I believe mine has always been in OD. Does it recover the same way when you are stock vs. propane?
A lot of questions, I know , but I sure would like to figure this ting out.
Leo
Always in overdrive. When stock I was pulling about 6000 lbs up a moderate hill. I manually dropped it into third and it came back. I beleive I only had 5 or 6000 miles on the truck at the time.
With the power down it recovers the same way. 10 or 20 seconds and i feel it start coming back. It just doesn't come back instantly. It ramps back. Feels like a controlled power up. Now if I drop the shifter manually then put it back in OD, it usually comes all the way back.
For others reading this I want to reiterate the frequency that this occurs....
Never happens if I run without propane and stay under say 65-70 mph.
Sometimes happens without propane when really pushing 80 mph.
Often happens with propane on a long sustained 70 to 80 acceleration.
Sometimes happens no propane, pulling.
Worse in the cold.
How many times lately? Last week three power downs and one limp. Those I believe because it just got cold in the mornings.
During the summer it would only do it on the 70-80 acceleration, lp on.
Hoot,
just a far fetched idea here, but do you have a high idle switch/setup?
I do have the high idle (see sig) but it was doing it before I installed it and before I had the updates done and before I modified anything except larger tires.
hoot,
well if it was doing it before,then it's not what i thought.
When I left my high idle switch on, I experienced the same thing you discribed...not all but some times.
just thought maybe your hi-idle wires were shorting on or summin.. :confused:
I searched this topic, and this sounds similar:
"My truck has the same occasional limp-home episodes.
I have Juice V3.5, and towed my enclosed carhauler to Texas and back on Level 2. It did it once on the way down to TX, and at least 20 times on the way home. Here is what happens:
Driving under ANY throttle condition (uphill, cruising OR DOWNHILL/COASTING it will powerdown.
You can feel the truck "juggling" the power, surging a bit, then it can go into a "rrUUM rrrUUM rrrUUMM" type revving (in cruise control)and I thought it might be the TRANSMISSION thinking about downshifting but NOT completing it.
It THEN goes into limp mode, where rpm can't go over 2,000; power is low; and floor throttle below 2000 causes a downshift and SLOWS the truck because in LOWER gear, 2000rpm gives SLOWER speed!
I figured the pattern out--I had to let it just coast down to rpm around 1500-1800, then apply a little throttle, and it would UPSHIFT to a lower rpm/higher gear (lugs down some) and suddenly ALL FINE AGAIN! Could INSTANTLY floor it to MAX, including UP TO LEVEL 4 JUICE, and NO problems...until the NEXT _RANDOM_ time the "limp home episode" happened again.
Limp home would last between 5 seconds and 20 seconds...basically, trying to keep throttle floored kept it in lower gears/higher rpm which delayed it getting below ~1500rpm so delayed its "resetting" itself. Switching between level 2 or 4 did not seem to change matters. It was NOT RELATED TO WHAT POWER I WAS USING, seemed RANDOM.
I have 30,000 miles on truck and haven't changed fuel filter yet, but it looks like filter did NOT solve it for Fasterthanyou. I will change the filter anyway.
The truck has had a "Service Engine Soon" light since these episodes started happening on the trip, and still has it now, so something must be unhappy in the ECU computer, some flag getting to critical and resetting. Can I find out what that code is MYSELF or do I have to get a tool or go to dealer?
Do the newer Juice updates have this or FIX it?!?"
xwing
Yes there is an upgrade to fix your reving problem,hopefully the bal of them problems too ......I had it happen but once low speed.....Reved only once,was in level 3 or 4 Super Juice....You should be able to go to a local Autozone and get the stored code.....If necessary....
MAC :D
That does sound just like my power down.
He is using the "limp" word but I think when the Ally goes into limp, you have no choice but to pull over and shut the truck off to get a reset.
Maybe the powerdown is a precursor to actually going limp?
jcummins
11-08-2002, 06:54
I've been following this board for several months, and it's time I jump into posting. I bought my Duramax 3 months ago. I have pulled a heavy fifth wheeler (14000+) about 60 miles, and other than that I've just drove it. I like this truck, but that pull told me stock form isn
jcummins,
You are the man with the exact same issue as me. I knew sooner or later people would finally start coming out.
It definately happens easier when the truck is not up to operating temperature.
It is aggrivated by power enhancers like proane or boxes.
I believe some of the people having problems with the Juice aren't really Juice problems. The extra power brings out this quirk.
Now all we need to do is find out what is doing it.
John Kennedy..... any ideas?
SoCalDMAX
11-08-2002, 11:43
jcummins,
Very interesting phenomena with your truck. At first I thought possible clogged fuel filter giving intermittent problem, or low fuel not getting picked up on a slope or turn. It odes seem like a little air in the system or low fuel pressure, but we can't discount an electrical problem, these things have more sensors than bolts nowadays.
I've had both problems, the fuel filter clogged but good and truck wouldn't get out of limp mode until filter was replaced. The other instance was I had 1/4 tank of fuel indicated and came down a long hill. Pulled up to light and it totally died. Wouldn't restart until on level ground and reprimed. Symptoms were different, but I wonder if it was a difference of getting a little air vs lots of air.
BTW, 10,000mi in 3mos? Wow, you're doin' a lot of drivin!
Regards, Steve
Steve,
Fuel flow may well be the problem. With suction feed and a dense fuel filter, maybe the colder fuel is unable to flow fast enough?
Or.... that pressure control valve in the HP pump???
Maybe I'll get lucky and the HPFP will take a dump like so many have and the new one will cure the problem?
[ 11-08-2002: Message edited by: hoot ]</p>
chuntag95
11-08-2002, 13:26
hoot,
Maybe you need to be the first to install the extra filter and booster pump? If fuel flow is the problem, then that should help it, plus you get cleaner fuel to the injectors and factory pump.
jcummins
11-08-2002, 14:50
I'm near Houston, and for this area it was chilly this morning. I did notice the transmission temp was quite low. I was about 5 miles from home when it did it the first time.
Yep, 10000 miles in three months, part of a work relocation to Pittsburgh. Next three months won't be that bad.
chuntag95
11-08-2002, 15:55
jcummins,
When you say "fell on it's face" can you be more specific? Did the engine act like it was going to die on you? Did if feel like the Allison was in nuetral? Was is just bogging down?
jcummins
11-08-2002, 16:07
The truck just stopped accelerating. I never thought it was going to die, but probably would have if I had not just read about this. Throttle at 3/4 and it was slowing down. When I let off, then feather the throttle back on, it was still slowing down. If I had to discribe the feeling in any one way, it felt like it was not getting fuel. I certainly want to get to the bottom of this before I do any more mods.
CntrlCalDmax
11-08-2002, 20:30
Did about 500 miles today, half loaded with a propjet engine and the rest empty. The "power down" happened twice, once going and once coming home. Both times truck had been at operating temp for more than 2 hours. Both were at light power settings. Both times I could recover by letting power bleed off until I was below 50 mph and the converter unlocked. During the second ocurrance I noticed the tack needel bounce like an intermittent short. This leads me to think it might be an electrical porblem of some sort. Fuel filter was changed about 8K miles ago and I had plenty of fuel.
Leo
Yep,
That's the symptoms. I don't know about the tach jumping but it's not an Ally limp. It's simply backing off. If you apply throttle it gets worse. If you let up and kingd of caost for a while, she comes back in a bit. I also tried dropping into third. That seems to get it back too.
CntrlCalDmax
11-09-2002, 16:15
hoot,
I noticed we both run an Amsoil air filter. Do you think we could be using too much oil and creating a problem of oil on the MAF sensor?
Leo
[ 11-09-2002: Message edited by: CntrlCalDmax ]</p>
That's a possibility. Mine still has the stock oil charge. I don't remember if I had the Amsoil when it happened the first time.
Can you unscrew the MAF sensor from the outside to inspect it?
[ 11-09-2002: Message edited by: hoot ]</p>
With my 454 and K&N I had similar power problems and found that I had overoiled the filter and the MAF sensor became coated with oil and junk and was apparently causing the problem. I run carb or injector cleaner into the throttle body and solved it. It very well could be that you have an overoiled filter and it collected enough junk on the MAF to start having power problems.
hoot
Yes, you can but you'll need an ultra fine flat head as the have tamper proof screws in.....
As I see it this must be the avenue to take to release the beast of power with'in .......
It's the only thing that they try for us not to mess with .....Look at Dodge they put warranty void tape on there fuel electrical connections......
MAC
I removed the MAF sensor and fount it to be clean with a very light film of oil on it. I don't think thats the problem. I did find the o-ring damaged by poor installation. You don't think that could cause the problem?
Mackin, tne small screwdriver worked perfect.
Just got back from a test drive. I was not able to get it to power down.
The real test will be tommorrow morning on the way to and from work.
I would be a crime if it was just the o-ring problem since day one.
Dave_WB3FYV
11-10-2002, 16:21
I had the same down-powering episode on the way to work 2 weeks ago. It was very humid with the temp around 82, but right where the problem occured - the the ocean and the bay come close together and the temp usually drops 5 degrees - and condensation forms on my windshield. I stopped, took off the Juice, restarted and drove on without incident.
There have been several posts about the Juice failing in the rain.
I don't know what your weather conditions were, but my truck runs a stock air filter, hopefully the MAF is still clean.
Also not sure if the moisture problem with the Juice is a problem in the truck that is just aggravated by the added power.
I'll put the Juice back on and try it again - taking careful note of the weather and other conditions. Could you do the same?
Brandenburg
11-11-2002, 21:00
Hoot, have you had the power down issue since fixing the o-ring?
Dave, I was one of the people having the issue with the juice and rain but I haven't had that trouble with juice 4.3. However, today when i went to take off from a light in town, the truck nearly stalled but didn't and then as I feathered the throttle, it slowly putted through the intersection and then picked up and all was fine. Is this the hot stall some of you other juice users have experienced? That was the first this had happened. I have noticed however, that 4.3 doesn't seem to be as smooth at higher rpms and occasionally gets loud.
Well I thought I had it licked but I got it to do it today on the highway. It was difficult to make it do it. It's hard to say yet if cleaning and fixing the o-ring did anything at all. I was on it pretty hard yesterday and today and it took quite a bit to get to to fall on it's face. If that's the way it stays, I'll be happy cause I normally would never drive it like that.
No change.
This morning I was able to force an SES and a defuel even after she was pretty well warmed up. I wasn't pushing it really hard either.
I'm gonna take it in and see if they can pick up anything with the scan tool.
CntrlCalDmax
11-12-2002, 08:00
hoot,
What do you do to force the power down? I would like to see if I can duplicate it for the shop. Please post the results of you shop visit when you know.
I would really like to find a solution but if I can't demonstrate it for the techs I know what the answer will be.
Thanks,
Leo
It seems to be temperature related.
Easier to do in the morning with cooler air/engine/trans.
During a warm day, I can make it happen by a sustained acceleration or sometimes just sustained run at around 70 mph on up to 80 mph. Usually occurring in a 70-80 push. Not WOT, just a passing type push. lp on.
On a cool morning,
Maybe 10 minutes backroad driving and then a few more minutes on the highway....
Just a moderate push probably in 4th or 5th gear from 50 to 60 can do it. lp on.
lp off it's real hard to make it happen.
EGT's never over 1250 in these examples. Usually in the 1000-1100 range on a push.
Does anybody know if the TCM/ECM does a defuel only during acceleration when slip is detected? The problem is this defueling doesn't come right back. You have to baby the throttle for a bit until it wakes back up. I hate it when that happens.
I'm also wondering if it's a fuel starvation issue. When it's cold out I'm sure there is a higher fuel demand. Fuel is harder to suck from the tank when its cooler. On hot days maybe 80 mph w propane requires a little more fuel than is available, flow wise?
[ 11-12-2002: Message edited by: hoot ]</p>
OK, Here goes.
This morning she did it. I guess around 50 mph I laid into it. After a brief acceleration she fell on her face. Came back fine in about 15 seconds or so but threw a code.
After work I drove straight to the dealer. I have an awesome dealer that works with me, no questions asked. As soon as I pulled up (SES on) I asked them to plug in while it was still running. This was like 5:00 PM. They are open till 8:00 PM during the week.
Three codes were set.
P0101 MAF
P0234 Overboost
P0700 Tranny
The P0101 was the last code set so it was the culprit.
I explained that it has been doing this since day one. He said he would need some time to research it. He got on the computer, printed out the troubleshooting stuff for P0101 code and went over to my truck. He pulled out my Amsoil aircleaner and said this could be the problem. It was pretty dirty I'm embarassed to say. But I'm still skeptical that is the problem.
He asked if I still had the original air filter. I do. Told me to put it back in and see if that cures it.
That's where I am now. Tommorrow I'll do the filter. It's dark and raining tonight.
I don't understand the overboost code. He didn't comment on that.
The best thing for me to do right now is take care of the filter and see what happens. The filter has 30,000 miles on it since I installed it. Never cleaned it. OOOps. I knew it was close to time but this issue has been with me even when th old filter was in. Maybe The updates I had done a month ago fixes the overboost but the dirty filter caused the MAF error. We'll see.
Duke.... ;)
I'm done over there in that sewer. Been fun.
[ 11-12-2002: Message edited by: hoot ]</p>
Hoot
The false over boost should have been corrected in the software bundle reflash.....If it was a falsh reading at the pcm....I still get it occasionaly,no reflash at all yet.....
I picked up a spare Amsoil on Ebay so I can clean one, oil, and put away for a spare....Got it cheap with oil, and a Allison spin on, off Ebay from a member that is no longer here (?).....
The one I took out had a little over 15k on it fairly clean ..The soapy water will tell if I ever get to it.....I got 14k to go before I need it .....
MAC
I put the old orginal (clean) air filter back in today at lunch. The performance gain was really noticable. I guess it slowly got worse so I really didn't notice it. We had a drought this summer so it was probably extra dusty.
I laid into it going over the Betsy Ross Bridge and it fell on it's face. Came back and has been ok since. I don't think the problem is gone yet but it sure does run it's arse off with the clean air filter.
The dealer will get it back with the OEM filter in it if this keeps up. So far they have been real nice about not noticing anything unusual (wink).
They mentioned they replaced one Dmax engine that threw a rod. Otherwise they have few problems. This was from their diesel tech.
As I suspected, the problem has not gone away with the OEM air filter in place.
I believe it's caused by the extra airflow/boost that the propane creates.
SES is on.
Seems to do fine when not on lp.
Does ok until I get to highway speeds on lp.
Not sure if I want to keep bugging the dealer.
Aren't you guys getting the same issues with the Juice and other power mods? You keep getting the Juice updated for power cutoff. I can't get lp updates ;)
SoMnDMAX
11-14-2002, 09:57
Get those codes checked again. Your dealer knows there's a potential problem, now get it fixed. You'll be much happier!!
They need to get the TCM codes out if the P0700 is set again.
It'll have to wait till next week. They are open till 8:00pm only mon-wed.
Amianthus
11-14-2002, 11:29
Just curious. Where in your intake does your LPG tap in? Is it prior to the MAF sensor? If so, I would be that the LP has gummied up your sensor. If you've already posted that you've looked into that and I missed it, sorry.
That's the only thing I can guess right now.
LP dumps in way past the MAF sensor. I'm beginning to be skeptical about the hose creating turbulence though. Read the air filter topic.
Looking for the a clean fitting/location to plumb the propane into the turbo intake. I have a brass 1/4 x 3/8 NPT fitting. I'm thinking of removing the plastic and stuffing a rag in the cast alum intake pipe and just drilling and tapping there right in front of the turbo.
Does the hose SHIELD or BLOCK air across the MAF sensor in any way?
pepperidge
11-14-2002, 21:24
Hoot,
I got my truck way back in Nov,2000
P0234 overboost code was a common occurence till GM finally gave me a temporary software fix in Jan. of 01 and then I believe the final software fix for that came out in april of 01. I'm told by my diesel tech that the software updates are selectable(dont know how true this is) Maybe your tech might have missed this one? or GM might have pulled this update out for another one (maybe newer but not quite the same?)The power down you refer to is exactly what I experienced for several months before GM gave me a fix. I know this is not much help but it does validate your claim that the power enhancer should not be the cause of the problem,only an amplifier. I am juiced and when towing (mostly level 2 sometimes level 4 when I start it and forget to hit tow/haul)I Push It!, have NEVER had the depower issue rear its ugly head. Maybe I'm just lucky, but I think it's a software issue.
Good Luck,
Pepperidge
Thought I'd add another vehicle to the list with this problem ... 2002 2500HD with 5200 miles, bone stock. Started her up this morning, pulled out of the driveway and instantly knew something was wrong. Drove easy on the way to work and noticed that there was no turbo whine (boo-hoo!) and couldn't rev over 2000rpm, couldn't maintatin 50mph without running 80-100% throttle and was difficult to get the trans (Allison) to downshift. At first I thought the wastegate was stuck open, but then read this thread and thought otherwise. Went out at lunch for a drive to try a couple of the suggestions listed here and nothing worked. Still no power. Let the truck idle in my driveway for ~10 minutes which seemed to cure it. Perhaps it's time to pay te dealer a visit and get the compters updated.
This site is great! You guys helped make my decision to go Dmax diesel.
More good stuff guys....
Thanks for the responses.
JK,
The hose turns down below the MAF sensor. It's not directly in the path of it. I'm moving it anyway.
pepperidge,
Thanks for the update info. You say selectable? You know as well as I do that there isn't a sure fire way for us to know if the updates were all done with on exception.....
Now my cruise control sucks. It has too much of a gap now between speeds. In otherwords, it constantly oscillates in a 2 mph window. Very annoying. I believe that's one of the fixes in the new software for cruise/downshift. Some fix.
Now are you saying they can load that fix but not the overboost fix if they wanted to?
Also, remember, the first code is MAF, not overboost.
bscotti,
Thanks. Maybe we'll get the answer soon.
pepperidge
11-15-2002, 13:30
Well I can't guarantee whatI was told was true but I do feel I can trust my tech I don't recall the other codes the truck was setting way back then but it was the
"overboost code" that was the depowering one.
I don't know how The tech support team works at GM as far as updating to a newer reflash they may delete the older sotware reflash updates as newer versions come out? But ever since mine has had the update back in april of 01 I havent had this happen, and now that I have the juice it still does not do it.
I know i probably won't be able to find my paperwork on it. But maybe that gm vci thing can tell me what updates I've had and you can compare?
I'll see what I can find and e-mail you the results I think your e-mail is still in your sig?
Later,
Pepperidge
pepperidge
11-15-2002, 19:40
Hoot,
You got mail!
Hey guys,
I know this is an old topic, but I was wondering if any new answers have been found. My truck can't decide if it wants to run good or not.
I haven't had time to play with mine lately. As soonas I get the laundry room remodel done I'll start playing again.
That reminds me, I have had my Amsoil air filter about 1.5 years, and 30,000 miles. Maybe I should clean mine this week? Thanks for the reminder!
Hoot,
This is the exact and I do mean exact thing that my truck is doing. I forced my dealer to do a report on it, since the first time it did it to me I almost got run over by a Semi truck.
I had posted this on this forum about a year ago and everyone came back telling me it was limp mode. Well when this happened my truck was bone stock.
And the error codes pulled out of my computer were identical to yours. And the dealer had already done the programing updates on my truck.
Way back when my truck was new and stock, I took my wifes Blazer for a "break-in" pull around town. I too got into a predicament just going up a hill on a four lane highway. Fell on it's face. Nobody had a clue. I was almost sure it was the tranny. SteveO gave me a lashing and he was right.
It's defueling and I don't think it has anything to do with the Ally at all. Well, we know it doesn't with the codes we're getting.
MAF and Boost.... what does this mean? We have the updates but still get the defueling and the codes.
I'm hesitant to take it in with the propane. They have been good to me so far but I hate to push it. I can't get it to do it without lp now. Only on lp. What do I do? Tell them it defuels on Propane :eek:
You need to get yours fixed so I can get mine fixed ;)
[ 03-11-2003: Message edited by: hoot ]</p>
a64pilot
03-12-2003, 08:47
Hoot,
Just read the whole topic, sure sounds like torque management. Have you disabled your wastegate? Reason I ask is with the K&N aircharger I was getting the the same MAF code until I added the dry outer filter, apparently the MAF was seeing airflow out of the MAP, just like JK said. Anyway disabling the wastegate would of course increase airflow, just like adding more unmetered fuel would, possibly enough to get you out of the range that the MAF should see.
The falling on the face thing sure sounds like the PCM/TCM backing off on fuel when a higher that desired Tq (computed, I don't think that there is a Tq meter or anything) is reached. Possibly Edge,TST etc. get around this with software.
I know the LS1 engine's torque management can be adjusted with LS1 edit, software that let's you change an unbelievable number of parameters in the LS1 cars. Only reason that I bring up the LS1 is that Tq management is very much alive there and it is a GM product.
Any way you may want to look into Autotap.
If it is torque management than why while doing 70 mph for about 5 minutes this morning, sustained, does it fall on it's face. I wonder what was taking place during those few minutes that caused the defuel?
I was running sustained. EGT's and Boost holding steady, not hard acceleration. 70 mph, propane on, after a few minutes it just crapped out in the hammer lane. I had to wait 20 or 30 seconds on light throttle, slowed to about 50, then power came back.
No I didn't do anything with the wastegate.
a64pilot
03-12-2003, 09:48
Hoot,
If you were on level ground and sustained speed, I agree it does not sound like Tq management. I mis-understood you, I thought it was occuring most under load like accelerations at high speeds etc. Now it sounds more like fuel starvation or something similar, I was trying to tie your MAF code to your power loss. As you stated earlier you may have seperate failures. I don't think that Autotap can read fuel pressure, but I think that the Tech II can.
Back to having the dealer Tech ride along while it fails.
Be interested to know what it really is, I know you'll keep us informed. Hope whatever it is it's found soon and is easy and cheap to fix.
;)
You didn't read me wrong. I can cause the defueling by accelerating while doing highway speeds. Or it does it by itself while maintaining highway speeds.
I don't have time right now but when I get another chance, she'll go back.
dmaxalliTech
03-12-2003, 20:00
Hope I can shed some light on this subject. The Overboost code is what is causing your fall on face, when pcm see's overboost, it cuts fuel for protection. Codes are most commonly set along with a 101 MAF code. I have tried desperatly to clean these with no avail. only solution is to replace MAF ( at least that i hav found). Programming obviously is updated to correct this concern, ( overbosst code) but it sometimes does not. Make sure all air inlet and intercooler hoses and clamps are tight and no leaks, Best way to go about checking is with T-2, with have 14lbs at stop. atmosphere pressure. max boost you should see with T-2 is 30-35 lbs. anything more will trigger code. Also want to make sure that wastgate is working properly, remove hose to wastegate and pull a vacuum should hold 15in of vacuum easily, then pressure hose to 45 lbs, wastegate should move freely. If all above pass inspection, I would lean on that MAF sensor, We have fixed alot of various concerns with that little bugger.. Extreme case would yield turbe replacement, have never had to go that far though.
Seeing repeated MAF sensor failure have impared my decision to update induction
My 01' did this after I installed the K&N air intake. I was getting all the same codes minus the p700. I took the air intake off took it in and they replaced the MAF and was fine ever since. Just never installed the K&N again. The truck was completley stock at the time.
I did have the Amsoil filter in. Tech told me to put the stock one back in. I did. No difference.
Thanks for the good technical info. I'll do what I can and use this stuff when I take it in.
BTW I have a SPA boost gauge. I rarely see anything over 25 psi (over atmosphere right?)
25 + 14 = 39?
[ 03-12-2003: Message edited by: hoot ]</p>
Hi,
I experience this problem after towing for about 75 miles, almost every 75 miles. Sometimes, if you turn on the cruise control it will catch. Sometimes, it just shudders horribly. It's usually best to just drift along and wait it out.
Has anyone found a fix? Since I tow frequently this is a real safety issue for me and I'm seriously considering trading this truck in.
Thanks!
Dan.
Hi,
The service department believes to have found the problem and fixed it. They say a fuel injector module was not reporting. I'll report back if the problem occurs again.
Dan.
Bobcat698
06-21-2004, 21:51
Originally posted by DanB:
Hi,
The service department believes to have found the problem and fixed it. They say a fuel injector module was not reporting. I'll report back if the problem occurs again.
Dan. Holy thread resurrection!
Hootie got rid of his Duramax since then anyway... He's driving a DODGE!! :eek:
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