Lately since I put my new 37's on, I had to change the tune to recalibrate the speedo and made some minor changes to the timing, boost, and fuel tables. It has been running rough and lopes pretty bad at idle only when it is cold, it smooth out a bit once you give it some throttle over 850 rpm. Once it warms up, the issue goes away. I changed several tunes and it still does it only when it is cold. I checked injector balance rates and they're in normal operating range, even checked cp3 (over 22k at WOT) as well. I doubt it is the FPRV because it would do it at all time, except this only does it only when it is cold. No codes popped, runs fine when it is warm. I keep thinking it is a fueling issue but I don't see anything wrong. Any ideas what it could be?
Rough idle when cold
- Thread starter Ridin'GMC
- Start date
I'll check that in the morning, going to replace the air filter and clean the maf sensor. This morning, it didn't idle that bad but after work it was worse. Is the actual rail pressure vs desired supposed to be the close within each other at idle? Brian has my logged tune in case you want to see it.
How much is too much timing on the low end? I didn't really change the timing on the idle part, just made changes to the cruising part at 1400-2000 rpm. It does run a bit too hot during mild grades, hits 1k egt due to the larger tires. I need to regear it to 4.10s.
When it rattles like dodge you have gone to far.
There are cold timing and FP tables.
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There are cold timing and FP tables.
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I compared various tunes to the one I made and they're not much off. So I lowered the timing tables a bit at the idle part. Loaded the new tune in the truck and monitored the conditions. Rpm bounce from 640 to 720, timing was at 6.5 (I looked at the table where I made the changes which is on "B" never touched others) that part caught my attention since the idle part was set similar to factory. I never touched other timing tables. I had my brother listen at the start up (mind you, I'm hard of hearing so I cannot hear precise details) he said it sounded like it was revving high but at a low rpm and had a knocking for a sec or so once it started up, then makes a chugging noise when it lopes. Once it hits over 75 degrees ECT, the issue goes away. I know this is not a tuning issue. Perhaps a bad sensor that's causing it?