Did your mileage improve?

 

I intermittently notice this same issue...I haven't thought of taking it in yet, but now that I am seeing it could be a spark plug issue that would sure be an easy fix if true...

 

Mine does it too. 2006 Auto 2.2 with IMCA muffler. When I stop its fine for about 25seconds, then a rough idle, drop in RPM and then it is fine again. I thought it was because of the new exhaust, but now come to think of it I always have the A/C on when it does it. I will have to see whithout A/C.

 

I too get a little shudder (2.4 auto) when stopped at a traffic light, but intermittantly. I asked a friend who is a GM service technician and he said he didn't know of any TSBs about that problem. I have 24200 miles on the car and have just ignored the shudder, but a little dark worry keeps popping up in my brain when that happens.

 

GM must have been aware of an idle speed stability issue. On older (2.4 only) ECM calibrations, there was a +/- 40 RPM tolerance on idle speed before correction. The latest calibration now has that lowered to +/- 8 RPM for a more stable idle speed.

Anyone experiencing this issue may want to ask their dealer about flashing the latest ECM OS calibration #12607442).

 

I've noticed it a couple of times stopping for a traffic light. It comes back real fast. I don't worry about it.

 

Just got thinking about this again in the last week or so. On another thread I posted a good day. This was because I painted some engine pieces, new pedal pads, and got a new magnaflow muffler installed. Only reason I mention this, I don't have the idle drop down anymore! I have been running a CGS intake for a while and noticed nothing different, but adding the muffler it changed. I don't know why or how, maybe something to do with the back pressure or lack thereof, but it seems to have gone away! Also mileage has gone up. First tank alone I saw a 2 mpg better then before.

 

Resurrecting my old post here...

I took my car in for an unrelated problem or so I thought. I had a check engine light on and a P0300 (misfire) code. They determined that it was a problem with a fuel injector or injectors. Once replaced I noticed that my fuel mileage has improved and I have yet to experience the rough idle problem. Time will tell if this truly fixed the problem but it looks promising so far.

 

Mine has had the same problem. I thought it was bad gas at first but after a few cans of dry gas and 7 takns of gas at a different station I have surmised it's not the gas.

It happens both hot and cold idle with the clutch in. Some days it almost stalls.

Good ol GM quality

5K miles on her so far. I noticed it at 3K miles first.