rough idle

[timgco]

So, we have about 5,387 miles. We have had a rough idle from almost stopped to a complete stop. It's worse with the AC on. We took the H3 in today to get "THE UPDATE" done to the computer for this issue. They also replaced the battery. It had a bad cell. This took about 1.5 hours to complete and they sent us on our way. I went to pull out of the dealership and the truck almost died out. The idle dropped below 500 rpm. It normally stays about 500 or just a little higher while stopped but has a rough idle like it wants to die. The service guy tells us the compter has to relearn itself and may take a while. he also told us this update did not specify what it was for, but they would try this. This pissed me off because the service manager was off today, but told the other guy that we would be coming and it that he knew what to do. I wouldn't mind so much bringing it in, but they are over an hour away!
Also the tech told me that know codes got thrown. Wouldn't a code get thrown from the bad battery?
Does anyone know what the update is suposed to be?
has anyone had the update and fixed this issue?
Thanks,
Tim.

[timgco]

So, we have about 5,387 miles. We have had a rough idle from almost stopped to a complete stop. It's worse with the AC on. We took the H3 in today to get "THE UPDATE" done to the computer for this issue. They also replaced the battery. It had a bad cell. This took about 1.5 hours to complete and they sent us on our way. I went to pull out of the dealership and the truck almost died out. The idle dropped below 500 rpm. It normally stays about 500 or just a little higher while stopped but has a rough idle like it wants to die. The service guy tells us the compter has to relearn itself and may take a while. he also told us this update did not specify what it was for, but they would try this. This pissed me off because the service manager was off today, but told the other guy that we would be coming and it that he knew what to do. I wouldn't mind so much bringing it in, but they are over an hour away!
Also the tech told me that know codes got thrown. Wouldn't a code get thrown from the bad battery?
Does anyone know what the update is suposed to be?
has anyone had the update and fixed this issue?
Thanks,
Tim.

[f5fstop]

Engine Rough Idle During Initial Warm-Up After Cold Start and Diagnostic Enhancements for DTC P0507 (Reprogram PCM) #05-06-04-053 - (Aug 25, 2005)
Engine Rough Idle During Initial Warm-Up After Cold Start and Diagnostic Enhancements for DTC P0507 (Reprogram PCM)
2006 HUMMER H3

with 3.5L Vortec Inline 5 Cylinder Engine (VIN 6 -- RPO L52)

Built Prior to VIN Breakpoint 68125462

Condition
Some customers, with vehicles built prior to VIN 68125462, may comment on a rough idle condition starting 5 to 10 seconds after a cold start when the ambient temperature is in the range of 10 to 26°C (50 to 80°F). This condition may last for up to 30 seconds before the idle speed will smooth out.

Correction
Reprogram the PCM with the latest TIS calibrations.


Only bulletin I could find with reference to rough idle.
Now, if the new program also overwrote the TCM functions, the transmission has to relearn the transmission adaptive pressure, and this can take a few miles. Not sure how this would affect idle, but it could.
As for the battery, the PCM does monitor the charging system, and if there is a dead cell the generator should be on full charge more than usual, but this may not actually set a code.
Hopefully, before they replaced the battery they did a diagnostic check of the engine charging system.

[timgco]

The tech said when I started the truck up in th bay, the lights were dim and found a bad cell in the battery. We put 200 miles on since the dealer "fixed" this. The ruck has beenon and off a dozen times since also. This rough idle has had few diffferent tanks of gas in it, and also from different stations. The rough idle is when cold or warrmed up. The only thing i haven't tried is a high octane gas. I have been using the cheap stuff. I am under 1/4 tank now, so I will try this next I guess.

[f5fstop]

Just curious, you haven't installed any aftermarket equipment such as a radio/GPS/CB?

A rough idle can be caused by various reasons, one being aftermarket items added that are causing EMI with the PCM. Other reasons are small vacuum leaks (easily diagnosed with a propane tank), bad plug, injector, leaking fuel in pressurized side of system, contaimated fuel filter, small amounts of water in tank (have you run a can of dry gas through the tank).
Most technicians seem to want to blame the electronics, forgetting about the basics of how an engine operates.
Good techs who really know the basics of an engine are hard to find, and when you find one, you want to tie 'em up and hide 'em in the garage.
It should not be the octane of the fuel, octane only affects the propensity to explode
rather than simply burn when mixed with air and ignited. Exploding is bad. Burning is good. The higher the octane, the more resistant to exploding.
I would be amazed if higher octane solved the problem, but if it did, then I would let the dealer know and have them look at some sensors.

[timgco]

The only thing added to the truck for acc's are 3 sets of PIAA lights. They checked into that too and found ZERO. So, it will go back to the dealer next week. thanks for the info.

[f5fstop]

No, would have to be some type of electromagnetic interference, and that won't come from PIAA lights.
It almost sounds like something basic. Hope you get it fixed; if I lived out in CO, I would stop by with all my equipment and do some troubleshooting.