Grebas94Z28

Ok, here's the big problem that has been intermittent based on things I've done. Once the car is warmed up and I am driving in traffic or not. Just when I stop at a light and am in Drive. It is idling fine at about 5 or 600 rpms and then as I sit there stopped it starts pulsating up to about 1,000 rpms. Sometimes it stays high until I start moving again others it fluctuates between 500 to 1,000 rpms anywhere in there until I start moving again. It doesn't do it all of the time or at every light also. When it gets bad it usually keeps it up until I shut the car off for a bit. I even took it to the dealer last year and they cleaned the intake and claimed it was just carboned up. It did help for awhile and then eventually came back. I thought maybe EGR was causing it, it's not. I have eliminated the EGR and it is still doing it. I may think it is some type of sensor, maybe just bad carbon buildup, if so how should I clean it? Has this happened to anyone else? I had scanned it last year when it was doing it and it threw no codes. This is really starting to get on my nerves now, good thing is I can put it away for the winter soon and not think about it. I really want to know why it would do this. It could be opti or plugs, or wires, but all of those have been replaced within the last year or so less than 10k miles. Maybe fuel somehow? I've also replaced the fuel filter, so... Any thoughts ideas, please help?

ChickenScreamer94

Unfortunately this seems to be a little problem for many member on this board. No one really knows what it is. I myself have this problem. I have replaced my IAC and IAT to rule those out for ya, and I replaced my fuel filter about 5k ago. I kinda think it is my plugs wires because i had my a/c comp replaced and i think they have bumped my plug/ wires (it started right after they did it). I had read an article that said plug wires develop minute holes that increase resistance as they heat up. Hopefully someone will figure out this **** problem!

Grebas94Z28

Ok, well that is good to know that it's not the IAC hopefully if my is the same case as yours. I was thinking that awhile ago, but thought there would be an error code. Yeah I am thinking about the plugs though because I don't know how much I trust the guys work who did the tune-up on my car since he said it was the worst car he ever changed plugs on. So maybe he did a sh***y job and that does kinda suck for me. Or maybe like you said the plugs may have just formed some spots and when they get hot. Well I was also looking and the far back plug on the passenger side could maybe be affected by the oil leak and that could maybe be causing it as well. Hopefully someone may have more of an idea. Thanks, keep searching, and does yours do it just as I have described it?

ChickenScreamer94

my car does exactly what your car is doing. It is a common thing around here, but no one knows why it happens. I am just gonna start replacing sensors until it goes away? It is expensive but i dont have a scanner. Maybe take it to the dealer? Something will come up in a few days i hope.

ThotYouKnew

with my M6....my idle constantly sits at 1K...always has...always does...is this not normal?

Grebas94Z28

I don't think it is normal to sit at 1k rpm idling with a stock engine. For a M6 it may be a little higher than auto, but an auto should idle around 5 or 600 when warmed up which it does occasionally when it is being good, lol. Chicken just go to auto zone or murray's and rent their scan tool, it is free, you buy it and return it when you are done get your money back, it is part of their tool rental programs. Other places might do this as well just ask around. I have used it on my car however and not found anything that was useful. For free it's a place to start though. I wouldn't just start replacing sensors that are potentially good though.

jim88iroc305

Same here when looking at stock tach; although when i hook up autotap the rpms scan in the high 800's.

CrockRocket94

I have the same problem. However whenever I turn the AC on the voltage goes way down.. and the car almost starts shaking?

Anyone have this as well?