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Discussion Starter #1
got a 05 2wd just put all new injectors and fpr in it and it is rough in park and neutral only when it gets up to temp, in drive its perfect, on the road perfect, it's drivin me nuts.

had a compression test came back fine, pulled the wiring harness and fine, ecm flashed, dont have a tune, its bone stock.


anybody got any ideas?
 

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Id say look for an air leak somewhere in the fuel lines. You wont see it unless you have a lift pump because its sucking air not pushing fuel out, check your fuel filter head, the rubber lines from the FICM and be sure to only run acdelco or racor stock filters. Others cause problems.


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well had a power balance test done today and he said while it was cold i think 7 and 2 where pretty much not there and when it got warm 5 and 8 were no where to be found. so he's thinking that the ficm is bad, and as most of you know they aint cheap.

Ill ask him about the air leak in the fuel lines tomorrow, until then any other ideas?
 

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well had a power balance test done today and he said while it was cold i think 7 and 2 where pretty much not there and when it got warm 5 and 8 were no where to be found. so he's thinking that the ficm is bad, and as most of you know they aint cheap.

Ill ask him about the air leak in the fuel lines tomorrow, until then any other ideas?

Sounds like you had a balance rate test and had some inconsistent readings. It is quite rare for the FICM on a relatively stock truck to go bad so I would first be looking at injector connections (make sure all are ice picked) and take care of any FICM wiring harness (rubbing at the alternator bracket). Beyond that I would want to see fuel pressure (actual vs demand to verify FPR operation) and double check your EGR.
 

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Discussion Starter #6
Wasn't the ficm, this truck was doing this before the injectors were changed, they took the wiring harness completely off and looked over it, the guy that has it is about to go crazy.

again when the truck is in drive it idles fine, runs like a scalded dog but in park everything goes nuts.
 

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I would have someone check the output on your cam and crank sensors too. If all looks good there, then run some clear vinyl hose between the fuel filter and your injection pump to make sure you don't have any air bubbles (air leaks). If that looks fine too, then it's probably an injector or wiring issue.
 

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teleman 777,
Did you every get this resolved? Mine has just started doing what seems to be the same exact thing. Everything is great, idles fine, until you get it up to operating temps (around 185) then it is still perfectly fine while in gear, but the second you put it in Park or Neutral it starts loping pretty bad. According to my CTS rpm's jump from around 660 to 690 then back and forth. Then you can stick it back in gear and goes back to idling within an rpm or two of 680 like it should. The warmest I have had it idle and not lope so far is 165, so somewhere between 165-185 something seems to be happening.

I did just swap positions on my injectors 7 & 5 last Saturday, but did not have this start happening till the last couple of days. It has been doing it since this last snow came through and temps dropped from 65 over the weekend to low 20's and single digits over night. So maybe that could be part of the puzzle too.
 

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teleman 777,
Did you every get this resolved? Mine has just started doing what seems to be the same exact thing. Everything is great, idles fine, until you get it up to operating temps (around 185) then it is still perfectly fine while in gear, but the second you put it in Park or Neutral it starts loping pretty bad. According to my CTS rpm's jump from around 660 to 690 then back and forth. Then you can stick it back in gear and goes back to idling within an rpm or two of 680 like it should. The warmest I have had it idle and not lope so far is 165, so somewhere between 165-185 something seems to be happening.

I did just swap positions on my injectors 7 & 5 last Saturday, but did not have this start happening till the last couple of days. It has been doing it since this last snow came through and temps dropped from 65 over the weekend to low 20's and single digits over night. So maybe that could be part of the puzzle too.

Brent, what does your actual vs demand fuel pressure look when the loping starts?
 

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Haven't had a chance to check that yet, was going to check that when I get home from work here in about 30 minutes. I'll report back with what I find.

Anything else I could monitor with the CTS that might be helpful to know?
 

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If it was gas I would say coolant temp sensor but its not. My truck has a skip at idle in gear and out it also feels like it has one driving down the road so any help would be nice
 

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Haven't had a chance to check that yet, was going to check that when I get home from work here in about 30 minutes. I'll report back with what I find.

Anything else I could monitor with the CTS that might be helpful to know?

I'd look at:
Fuel Temp
Throttle Position
Intake Air Temp
Engine Coolant Temp
Demand rail pressure
Actual rail pressure
 

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I'd look at:
Fuel Temp
Throttle Position
Intake Air Temp
Engine Coolant Temp
Demand rail pressure
Actual rail pressure
Alright, sounds good. I'll go get some data and see what we come up with.
Thanks
 

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Well, I did a couple videos but am having trouble uploading them to photobucket with good enough quality to even see.

I checked it three times. I checked when I started it to leave work. It idled as smooth as could be with the following specs.
Fuel temp - 55 F
IATM - 37 F
ECT - 93 F
Throttle - 0%
FRP - 5.8 Kpsi both A & D, varied by no more then 0.1

Drove home 20 min drive. Loping pretty good in park, enough to rock the truck.
Fuel temp - 73 F
IATM - 33 F
ECT - 183 F
Throttle - 0% (did not fluctuate at all)
FRP - 4.3 Kpsi both A & D, varied by no more than 0.1
RPM - jumping from +/-665 to +/-691
NOTE: Just like before I could put it in gear and it would smooth out and settle right at 680 rpm like it should and only jump a few rpm either way. However this time unlike all the others when I put it back into park it stayed smooth. This so far is the only instance out of 6 so far that it did not go back to loping. All the other times it was loping so bad that I could not even check balance rates they just read 0.0. I did check my balance rates this time since I got it to smooth out and the farthest out was +0.8.

I thought that was unusual so I took it down the street and back to see if it would lope again and sure enough did the same thing with the same specs as above except fuel temp was up to 77 F and IATM was up to 37 F. This time when I shifted it from drive back to park it started loping again though not as bad.

I should note this was the warmest outside temps it has been since this started happening outside temps of right at 30 F. I am thinking this could have something to do with my findings, since it didn't start doing this until temps got down into the low 20's, or I could just be grasping at straws.

I am going to try to data log more info tomorrow morning, when it will be much colder, with my V2.
 

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Good info and I should have asked what the turbo vane position was as well.

Definitely log it with the V2 (Duramax LBZ PID) and post it up here for us to have a look.
 

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Alright well I setup my pids last night before bed and then this morning didn't have enough time to change them before heading to work so I didn't have the LBZ pid list, but see what you think with these log files.

I did plug the CTS in to check vane position, since I didn't have that on my pid list and it stayed right at 34% and didn't change any.

Break down of the included log files:
E60-20 - Logged entire trip but cut out the middle between the cold idle at startup and the warm idle once I got to work. It was doing it during the warm idle. (obviously a 20 min log file is too large to post)

E60-21 - Logged idle after trip to lunch

E60-22 - Idle after trip back from lunch

E60-23 - Drive home from work same deal, cut out the middle, only left in startup idle and warm idle at end of trip.

It was warmer today nearly hit 60 F. The lope isn't nearly as noticeable when its warm out, even though the rpm's jump about the same amount it just doesn't rock the truck near as much for some reason. It was doing it when I got to work.

I guess take a look and see if you notice anything unusual I don't really know even what to look for in them, I haven't done a ton of stuff with logging and analyzing data.
 

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Brent, I had a quick look at the log files and the thing I found most strange is that your engine temp, fuel temp and IAT suddenly jumps up (jump happens in a single frame of data) for no reason at all. That's way too fast to be real input so this makes me think maybe you're dealing with a wiring issue on this because it's all the temp sensors (likely the 5V reference circuit), not just one. I would be looking all over the wiring for possible causes (shorts, chaffing, bad grounds, poor connections, brackets rubbing, etc).
 

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Brent, I had a quick look at the log files and the thing I found most strange is that your engine temp, fuel temp and IAT suddenly jumps up (jump happens in a single frame of data) for no reason at all.
I think what you are seeing is where I cut out some data from the log files, because they were too big to post. If you compare where that jump happens the vehicle speed should be moving, indicating that I had either just taken off or am coming to a stop. I probably should have just divided the file into two files (cold start idle & Warm after drive idle) but I just didn't have much time and it was fastest just to cut data during the drive out of the log.

I myself haven't even had time to take a look at the files other than to edit and post em.

Hopefully I will get a chance soon here to log with the pid setup you initially wanted me too.
 

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I think what you are seeing is where I cut out some data from the log files, because they were too big to post. If you compare where that jump happens the vehicle speed should be moving, indicating that I had either just taken off or am coming to a stop. I probably should have just divided the file into two files (cold start idle & Warm after drive idle) but I just didn't have much time and it was fastest just to cut data during the drive out of the log.

I myself haven't even had time to take a look at the files other than to edit and post em.

Hopefully I will get a chance soon here to log with the pid setup you initially wanted me too.

Ok good to know, then if those files aren't continuous then that would explain the jumps.

What's your Airdog lift pressure set at BTW?
 

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What's your Airdog lift pressure set at BTW?
I was planning on verifying that this weekend. I thought about that possibility as well. When I installed it I just put it on, since they are supposed to come preset to 8 psi. I figured if it was too much it would idle rough right away and I would know, it never did till now but still worth checking for sure. Sure would be nice if that's all it was.
 
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