03 LB7 running rough

[Ryan03]

I have an 03 2500 LB7/allison. I have owned it since new, it currently has 94k miles on it, and has had an Edge juice installed on it since 7k miles. Recently, I noticed the engine seemed to be running rough when coasting to a stop in traffic, almost like it is running on 7 cylinders, once stopped, it idles smoothly, until I take my foot off of the brake and idle forward, then it runs rough again. I can duplicate this problem 100% of the time by holding the brake pedal with my left foot with the engine idling in drive, while ever so slightly depressing the accelerator with my right foot, just barely pressing it.

Sometimes when it is running rough, I can smell strong diesel exhaust fumes, but have been unable to get a look at the exhaust to see what color the smoke is. For the past year or so, after a cold start, while putting across a parking lotunder very light throttle, the truck will all of a sudden, seem to lose all throttle imput momentarily, causing it to suddenly slow down, then after about a half second of this one time occurance, is fine.

I have been driving for 3 days with the edge removed, and it has had no effect on the problem. I think I am getting a slight, and I do mean slight amount of diesel in the crankcase, due to the oil level increasing about 1mm in 2500 miles, although the oil condition appears to be very good still, visualy speaking. I plugged in my scanner, and no codes have set, and none are pending.


The truck still has all of its original injectors, and other than the edge, is ALL stock and has been very well maintained. I think that one or more of my injectors are headed south, and have already spoken with a dealer about the 7yr 200k warranty. He basicaly said that it is a 4 hr process to diagnose the injectors, and if they don't find anything, I'll have to pick up the cost for diagnostics.

Any imput or opinions regarding the rough running and or 200k injector warranty policies would be greatly appreciated.

Thanks, Ryan

[DmaxMaverick]

Your injectors are going south. Simple as that.

The rough/smooth idle you are duplicating is the balance/no balance feature of the fuel injection control. When the engine is warm, with less than 1% throttle input, and less than 1 MPH, the PCM will balance the fuel injection event to smooth the engine idle. Once you roll off, or give it throttle, the balancing turns off. If you read the balance rates and PWM (with a scanner), you can see this happen in real time.

1mm increase in oil level, IMO, is negligible, and not necessarily an increase. Once you start making oil, it won't be so subtle. Get this fixed while you are still under warranty (and GM still has a store in the US).

[Mark Rinker]

What do your balance rates look like, at idle? Do you have one or more that fall well out of range?

Agreed, given the current state of GM, if they are willing to honor the warranty, now - my advice would be to get all 8 done - now...

However, if they don't feel it is necessary/warranted, I'd have them

document your symptoms;
document the date, mileage, and results of their diagnositcs;
document the in-service date of your truck, and their refusal to honor the injector warrantyThen, I'd start a regimine of fuel treatment, and try to extend the life of this set as long as possible. Having owned and run 3 LB7s, I can tell you that injectors can 'hang' or develop poor spray patterns, but respond well to fuel treatments, returning back to normal operation.

As DMaxMaverick said, if you start 'making oil' - you'll know it. Likewise with smoke at idle. There is no mistaking it - it leaves clouds when it gets bad.

Just my .02 worth...

[Ryan03]

What do your balance rates look like, at idle? Do you have one or more that fall well out of range?

Agreed, given the current state of GM, if they are willing to honor the warranty, now - my advice would be to get all 8 done - now...

However, if they don't feel it is necessary/warranted, I'd have them

document your symptoms;
document the date, mileage, and results of their diagnositcs;
document the in-service date of your truck, and their refusal to honor the injector warrantyThen, I'd start a regimine of fuel treatment, and try to extend the life of this set as long as possible. Having owned and run 3 LB7s, I can tell you that injectors can 'hang' or develop poor spray patterns, but respond well to fuel treatments, returning back to normal operation.

As DMaxMaverick said, if you start 'making oil' - you'll know it. Likewise with smoke at idle. There is no mistaking it - it leaves clouds when it gets bad.

Just my .02 worth...

I would like to take it in for warranty tomorrow, however the service manager at my local dealer scared me off a little when he said that I would be held responsible for diagnostic cost [4hrs], if they could not confirm the injector issue. Likewise, if GM folds, I am well aware of the cost of out of pocket replacement. Has anybody on here had GM reject theyr'e LB7 for the 200k replacement, if so were they chared for diagnostics and how much. I realize it is probably only a few hundred bucks, but in these current econimic conditions, is alot to me right now.

As far as the injector balance rates, my older Matco scanner will not give me that much info on the data stream, just OBD2 info for the most part.

[Mark Rinker]

If you know anyone with a Predator tuner, or Edge Evolution, they will read injector return rates.

[madmatt]

4hrs huh???? Gm gives us like 18 minutes! I'd offer to give him one hour tops if it didn't fall under special policy. Where are you located?

[Ryan03]

I am located 40 mi. SE of Cleveland Ohio. I felt that 4hrs sounded kind of excessive as well.

[madmatt]

dang,, was hoping you'd be closer to So. Ind. I'm not familiar with any good dealers in that area.

[Ryan03]

I dropped my truck off at the dealership on Monday for the rough running just off idle, as well as a little diesel in the oil. They called today to say that they were going to replace all 8 injectors under the 7yr 200k plan:D :D.

I have read a few post that more or less state a shorter life on the replacement injectors based opon peoples experiences. Is there any truth to this, and if so, how come. I am not complaining, a free set of injectors is way better than 4k out of pocket.:eek:

[Mark Rinker]

Probably a good time to invest in additional primary fuel filtration, with the money saved by your warranty, especially if your approach is to keep the truck around for another 100K miles.

However, if you intend to sell or trade the '03 in <50K miles, save your $$$ and use the fresh injectors as a selling point, as it is a very valid one.