Stumble ?- - - Miss ?

[D Vedder]

Hi,
For starters here are the specs.

1998 Chev. 2500 4X4 Ext. cab
227,000 miles
Original injectors
IP replaced once at 7,000 miles
No other work but services, batteries, fuel and 2 clutches.

The problem is I have noticed a surge, miss, stumble. It is really noticeable at 1800- 2000 rpm. right at my cruising rpm. My brother test drove the rig and found it to do the same thing sitting still at the noted rpm. Throttle position sensor?, Injectors ?, Pump ?

Any help would be much appreciated.

[charliepeterson]

This could be a fuel delivery issue. With the truck idling open the water bleed petcock at the thermostat housing. If nothing comes out, the truck will stall so close it quickly. The lift pump under the driver's seat force feeds the injection pump fuel. Power to the pump comes off the oil pressure switch down behind the fuel filter. While your near the fuel filter pull it out and make sure its OK.
The lift pump will hum when operating. Its not hard to change out just messy!

[rjschoolcraft]

Could also be the PMD.

[jspringator]

Dveddar, if I read your post correctly, you have gotten 220,000 miles on one injector pump and one PMD (FSD)! That is the best service I have heard of on this board. What is your secret? Fuel Additives, fill at 1/2 tank or what?

[D Vedder]

Not much of secret. I have used quite a bit of Stanadyne. Oil changes every 5,000. Only have used Delo 400. I found it is important to buy clean fuel, high volume outlets are best. I log a lot of highway miles , 45-50K a year. I must of picked up one them gems when I got this rig!!

[99gmccrew]

D Vedder, My rig is now doing the same thing. At about 55-60 mph it started bucking or loping while I had the cruise set. I tried it with the cruise off and still had the problem. This has happened three times in the last two days and has never happened before. No ses light coming on. I'm wondering if my boost controller is masking any possible codes. I don't know if this is my IP, but I'm kind of hoping it is because I've got 97k on the truck now. Would my warranty be voided because of any of my mods like the Intercooler I've installed? Thanks in advance, to those who repond.

Steve

[DKeen]

I have had the same symtoms. Here is what I have done so far, but no resolution yet!

New filter
New PMD w/cooler on fender
New lift pump
New electronic filter on pump.

Sounds like the next least expensive thing will be a OPS. However, after about a 6 weeks of this BS, the SES light came on. I will get it checked today and see what the codes say!

[ucdavis]

on the high miler that started the thread, you might consider the injectors as beyond their duty limit, and of course the IP output would be similarly weak.
The others, and maybe the oldie too, could have IP going out or just FSD. W/out codes I'd suspect FSD only. W/IP codes, the whole Stalling article checklist is next.
http://www.thedieselpage.com/members/tt99-9.htm

[Steve O.]

What's the suggested duty limit of the injectors?

As I've posted before, everything fuel delivery related on my truck is brand new, except for the injectors. Not sure when or if they were replaced prior to my getting the truck. Was going to put in hi-flows when I did the IP a few weeks ago but the new tranny, IP, FSD kit has sort of bled me dry as far as the truck goes. Looks like I may have to just go for it...

Steve

[Diesel Dan]

I still get an intermittent surge at idle with my truck. When it surges better have a good hold on the brake pedal. New IP/FSD about 5K ago, didn't change anything. New motor and injectors <2K ago, still there. I'm leaning towards the crank sensor myself. No codes. I've seen crank sensors do really funny things on EFI gassers in the past and not set the SES light.

[charliepeterson]

Surging can be a bad FSD. The four torx screws MUST be tight to transfer the heat away from the driver. On the back side of the driver under the two plastic caps are the drivers. The mounting screws can loosen on these as well.
Heat KILLS this component. As this fails if it is failing the surging can/will get worse. I've seen a truck act like cruise control when it didn't have cruise control. In neutral or poor road conditions the engine rpm's can try to run away as you ramp up.

[JohnC]

D Vedder:

Does your truck have EGR? Teh RPM range you mentioned is right about where you expect surging if your EGR is faulty.

[D Vedder]

ucdavis and JohnC, thanks for the replies. I think I am starting to lean more towards the injectors as they have seen an exceptional amount of mileage. I believe the service life of injectors have been estimated between 75-125K.
I have the OBDII scanner and still haven't thrown a DTC....go figure

[DKeen]

John C. - Since my truck is having the same symptoms as Vidders, can you give me some insight on how the egr will cause this. I am replacing the OPS sensor today. Still no codes but major stumble in the 2000 rpm (highway cruise) range. Replaced the Lift pump and FSD about a month ago. I will see if vidders injectors fix his.

[JohnC]

Originally posted by DKeen:
can you give me some insight on how the egr will cause this. I can't give any specifics, only that a lot of folks who have complained about stumbling in the 45 - 55 mph rang have had the symptoms go away after disabling the EGR circuit. Not a permanent cure on ODB II trucks, I hear.

[ 12-13-2004, 02:02 PM: Message edited by: JohnC ]

[99gmccrew]

I think I may have solved my surging/stumbling problem. I had gotten fuel at a station I don't normally buy from, so I checked out my fuel filter which had just been changed 3000 miles ago.
It was filthy. I replaced it and so far so good. I will give another update in a few days.

Steve

[rjwest]

99gmccrew: Info: I had my inj pump replaced by a
NON GM Diesel Shop ( after getting a run around at the dealers ).

Sent Bill to GM, they paid me in Full ( After I Called the Chevrolet 800 number.

[99gmccrew]

It's been two days and one fillup at the pumps with no surging. I think the problem was bad fuel which had clogged my fuel filter. After replacing the filter and filling up at a station with a big diesel turnover problem seems to have been solved.
I feel lucky, but I'm going to keep my fingers crossed.

rjwest: were you throwing any codes when you had your IP replaced? I bought a code reader and I'm showing no codes, awesome price for those who need one I might add:
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46030

[rjwest]

In 1 year of intermittent " quits "
Only once did I get a code. Inj Pulse to short "


My pump started to quite after warm up from
temps around 30Degrees, would quit several times
, than be ok the rest of the day,

Finally quit at 100 degs on a hill. Stopped in Missula MT, and replaced pump, Still running good.

I had a generic code reader from autozone,
Would not read Diesel specific codes...or history..
? Harbor frieght reader ? May want to ask...

Went to laptop program....Reads a TON of stuff, just don't know what it all is yet...

[99gmccrew]

Thanks for the the input rjwest, as for the code reader I'm not sure if it will read all diesel specific codes, but the instructions read applicable to all models since 1996 for generic obdII protocols. On the definitions chart I looked up (fuel pump driver module) and it gives a code #1233 & #1234. MAF sensor intermitttent #1100. Do these code #s sound correct? I hope I didn't buy too hastily.

[schamp]

My 97 suburban with 238k on it will miss or stumble under full wot. Doesn't do it other wise. Bought truck with 167k on it, with the report that the trans had been rebuilt at 100k and maybe a new injection pump at 100k. I may still have the orginal injectors. Injectors are noisy but truck seems to run pretty well and pull my 33 jayco camper ok except for the mountains around Bristol Tn. Been using some fuel additives. I was hoping to get Advant to build me a new engine but with the other thread ongoing I either want to see how that goes or use another company. I am in Georgia and hope I end up with Advant cause they are close. Don't want to pay 7,000.00 and have it die at 30k miles. Back to the subject at hand, I guess I could install some new injectors anyway and see how it goes. Going to change the filter first.

[99gmccrew]

It's been close to a week or so now after changing the fuel filter, no stumbles and truck is running great. My thought is it was a batch of bad fuel cloging it. I guess its just beginners luck.

I hope this helps some of you with the same problem. Cheap fix.

[DKeen]

John C.- How do you tell if you have an EGR? I have replaced OPS, lift pump, pmd and remote fuel filter. Still get the stumble, eventually.

Not sure what to try next? Getting frustrated! I bought the truck new in 1996 and it only has 70,000 miles on it. IP has been replaced by dealer at 58,000.

What are your thoughts on injectors, could that be the problem?

[JohnC]

Originally posted by DKeen:
John C.- How do you tell if you have an EGR?If your engine is an L56 you have EGR. If there is a big, ugly EGR valve in the top center of the intake manifold, you have EGR. If your GVW is less than 8600 lbs, you have EGR. If you have 3 vacuum control solenoids on the left side of the intake manifold, you have EGR...

[Billman]

D Vedder

Ever consider the timing chain?

[99gmccrew]

D vedder

I have gotten an intermittent miss once before when I had a loose battery connection. Have you tried checking all your battery and ground connections? Sometimes its the simple things that get overlooked.

99gmccrew

[Lenl]

I had a simullar problem with stumbling and I changed out the lift pump and filter and everything seemed fine for a few days then it was back again, finally traced it to the oil pressure sensor. It was going and would only provide intermitant juice to the lift pump. Changed it and no problems after that.