Mileage & Power GONE - New thread (no hijacking) [Archive]

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ssybert

11-16-2007, 13:04

Original post:

Hi Everyone,

My truck seems to have been losing power over the past few months. Symptoms included boost not coming up like it used to... stomp on the pedal and WAIT while the turbo creeped up to 16-18LBS or so. It used to launch right up to 20+ in about 2 seconds; much different now. The next problem I encountered was much less power. Just the truck pulling itself down the highway is VERY weak. getting up to 65 in enough time to merge after pulling out of the ramp tolls is sometimes sketchy. If I try to pass someone and keep that pedal on the floor, it will never shift up to 5th unless I let off the throttle; seems like there's not enough power to make the transmission shift. Next is mileage. In the toilet. No matter how hard I try, 12-13 is the absolute BEST I can get. Towing, forget it. It's close to 10 then. Last problem is I hear a mild surging @ idle. Nothing rediculous but I can definatly hear it and it never goes away.

I had the truck brought in for injectors a few months back (they did all 8) to try and resolve this and it didn't help at all. They also did a fuel filter at that time.

My information center is broken for some reason so i dont know if there are any codes. Just whatever indicator lights there are on the dash, seperate from the information center. At this time, none of those have ever come on other than the self-test at startup.

I'm reading alot around here about FPRV's and PDM's. I dont know which is the likely candidate or where I should be starting but I have to do something NOW. With diesel @ $3.45/gal around here, me buying a new home and having to make MANY 2 hour round trips, i think the cost of parts will pay for themselves in fuel savings in the up coming weeks.

Any suggestions anyone? My dealer and their mechanics are a bunch of knuckleheads and would rather GUESS myself than pay them for nothing. Any some REAL professionals can offer would be very appreciated.

Thank you,
Scott

Reply to Duramaster:

Ran a code scan on the truck with a friends Actron tool. No codes what-so-ever. He also has access to a Tech II (works for a Saab dealership). Should I try anything with the Tech II tool? This thing has me stumped. no codes, good filters, new injectors, not making oil... what gives? Dead turbo? Shouldn't the truck be throwing SOMETHING for codes? The transmission wont even shift under full throttle unless I let off th pedal. EGT's will just climb to infinity if I let it ane truck will sit @ 3K until I lighten off the pedal and this is UNLOADED up a mild hill!

More Power

11-16-2007, 14:05

Are you running any tuning/modules/programs?

Jim

ssybert

11-16-2007, 20:13

Nuthin' -- Bone stock.

More Power

11-16-2007, 23:53

I might try having the dealer upload the current programming. GM tinkers with the programming now and then, and yours may have developed a glitch.

I'd want the DIC fixed.

Your engine may have some sensor that works - sortof. Not bad enough to set a DTC, but impacts performance none the less.

Jim

Duramaster

11-17-2007, 17:39

What kind of truck is this? What year vehicle is this? I take it has a LB7 engine in since you mention having to replace all eight injectors. You mention that the DIC is inop. Is this a C-4500/ 5500 truck? If so, Is the DIC even plugged in? Sometimes people unplug the DIC when removing the IPC trim and they forget to plug it back in. This usually sets a P0380 wait to start lamp code. As far as what to do with the TECH2, try ramping the fuel pressure upto 160 MPA. It should do this at idle with no problem. With the fuel pressure at 160 MPA, sheck out the balance rates of the injectors. All should be in spec.

Are there any transmission related DTC'S? Hope this helps.:confused:

Mark Rinker

11-17-2007, 19:22

From his signature:

02 Chevy 2500HD D/A CrewCab ShortBox 69,000 miles

http://www.thedieselpageforums.com/tdpforum/images/misc/progress.gif

Duramaster

11-17-2007, 19:23

My bad............ I keep forgetting about the silly signiture. :D

ssybert

11-25-2007, 16:12

Sorry for the delay in response here... Holiday travel, end of year wrap up @ work, etc.

Anyway, I haven't had an opprutunity to get ahold of a Tech II yet but I did do a little more of my own diagnostic work.

Here's what I found:

I tried toying with the wastegate actuator by removing the vacuum line and going for a drive. I didn't know wheather or not the presence of vacuum dumped more exhaust or less so I gave it a go. Oddly enough, there was absolutely NO difference in performance. Lousy acceleration, no more than 16-17lbs of boost after staying on it WOT for many seconds... poor response, etc. Back to the house to investigate and I found that the wastegate lever doesn't move AT ALL. It's siezed solid. I tried to get up in there and move it by hand and it wouldn't budge. I tried both while the truck was running and without... with the vacuum line on and with it off. It wont move. I dont use the truck often and I'm guessing this is from excessive sitting. Maybe 5-10k per year, tops.

I assume this isn't normal behavior? I should be able to move this lever correct? What could it be, most likely the actuator or inside the exhaust?

Here are some pics of what I'm referring to incase I'm completely wrong in what I'm talking about.

Any ideas?

Thanks, Scott

DarylB

11-25-2007, 19:43

It's most definitely those leave on your cowl causing the issue along with that OEM Delco battry :P. For serious, no idea *Shrug*

DmaxMaverick

11-25-2007, 20:16

The wastegate is PRESSURE operated. NOT vacuum, like EFI 6.5's. The pressure supply comes from the compressor housing (follow the hose). The actuator is a "pull off", and is heavy spring loaded closed. You should be able to move it with some force, though not easily by bare hand. By the looks of things on your truck, corrosion could be at play. If the linkage is frozen or inhibited, it can prevent pressure dumping, and at the same time, prevent the gate from closing completely (hence the low boost).

Put some shop air pressure (no more than 40 PSI) to the actuator to verify it's working. About 1/8" rod travel should indicate (in shop air PSI) about the max boost you've seen. Rod movement should be smooth as you increase air pressure. It should hold fast until you get around 18-20 PSI, then move pretty quickly up to full open (~10 PSI more). Remember, the actuator needs to hold the gate closed at more than just the air pressure. The gate is under load from exhaust pressure when the engine is under load (making boost).

ssybert

11-25-2007, 21:53

DmaxMaverick

11-25-2007, 23:28

Try the shop air first. If it moves, it's good. If it doesn't, then remove the linkage. The lever should move easily with the actuator disconnected.

Your problem is unique. I haven't seen it before, so elimination of simple components is important. It could be a bad actuator, seized WG crank, corroded linkage, or something really simple like that. Stay at it and keep us posted.

More Power

11-26-2007, 15:03

Thanks DM... I thought I put some force on it but wasn't sure which way to really put my strength into it so it's possible I wasn't trying hard enough.

So to clarify... in it's idle position, I should be PULLING the rod INTO the actuator to test?

IN to the actuator = MORE boost
OUT of the actuator = LESS boost (idle state)

Is this correct?

I'll see if I can try this monday night. If it doesn't work, I'll pull the clip off the wastegate lever and see if that moves. Am I correct in assuming without the actuator rod attached the wastegate should move freely? i just want to rule that out if I can't get the entire assembly to move with air pressure or manual force.

Thanks, Scott

There is a pretty stiff spring in the actuator that pulls on the actuator rod. An increasing boost pressure will eventually provide enough pressure to oppose the spring and allow the actuator rod to extend slightly.

With 20-25 psi air pressure, the actuator should extend. This procedure makes it a lot easier to disconnect/reconnect the actuator rod on the turbo's wastegate lever. :)

Jim

ssybert

01-26-2008, 21:32

Hey guys, It's been a while since I last worked on this issue but I have some new info which may help narrow this down. I disconnected the wastegate actuator and checked the wastegate for manual operation. Worked perfectly. I then verified the actuator wasn't stuck in a partially open possition. Next, I just wired the wastegate closed entirely then took the truck for a ride. Exact same performance.... terrible. The turbo is showing boost but it builds very slowly. I had to tow a snowmobile about 40 miles today and found the EGT's to be very high and when climbing mild hills I was pushing 1200-1300 just to keep the truck moving with 7-10lbs of boost.

Keep in mind, I'm getting 10mpg loaded or not.

Does this sound like a FPR? I dont have the tools to check it and if the consensus is it's probably that, I'd rather put the money into the part rather than diagnosis.

With this new info, any new input or opinions?

Scott

ssybert

01-29-2008, 21:55

bump... :-o

DieselMonk

01-30-2008, 04:01

did you check the air filter and MAF sensor yet?

ssybert

01-30-2008, 05:01

Air filter is new but I haven't checked the MAF. Not sure how. I'll search here, see if I can make a derermination on that and post my results.

Thanks,
Scott