My S has about 16k miles on it right now, I made sure I've kept up with all the services, lately, the engine has been acting weird, sometimes after coming to a stop, the idle would drop way down to less than 300 rpm, and then it would come back up in a few seconds, another problem is that once in a while, after I started the car the engine would start reving to 2k-3k rpm by itself, it goes on for maybe about 10 seconds, the last time I stopped it I stepped on it and rev it to 4k rpm, has anybody have this problem before? Anybody know whats the problem? I've tried resetting the ecu couple times, I've wacked the map sensor, but it doesn't seemed to be working, I have an appointment with the dealership this week, but I would like to know the probabilities before I dropped off my car.

Thanks in advance .

 

Since you've already done the MAP whack and ECU reset, then I'm guessing that the ECU is still having a hard time learning and compensating for the dipping idle when stopping. It could still be a MAP issue (a new one perhaps?) but it could also be a faulty Idle Air Control solenoid/valve. Another possibility might be a vacuum leak someplace.

 

It may have lost the TPS signal... No CEL?

 

Could this mean that spark plugs need to be changed?? I have this prob too. Whenever I come to a complete stop the RMPS drop really, really low and the car almost stalls out.

 

I've had the same thing happen. It has happened several times but the only time it worried me was after driving three hours in hot weather and it did it every time I let off the gas with the clutch out. It almost stalled several times. After I got home and let it cool it hasn't happened that frequently since.

Mrcln1

 

I have had similiar experiences. Engine almost stalls once clutch has been engaged coming to a stop. I thought it could be attributed to my clutch slipping since I am supercharged. I have seen in the owners manual that it is possible to adjust the idle. Could this help?

 

It is very common for the idle to drop very low at stops. Resetting the ECU should actually make this problem worse, since the ECU has to relearn how the engine behaves during idle. The most probably cause for this behavior on a stock, non-defective F20C is climate changes. When the climate changes, the ECU has to adjust its idle parameters, which is a relatively slow process.

If there is something wrong, then I think xviper nailed the possibilities. I had a leaky oil catch can that caused all kinds of weird idling problems. The only other possibility that I can think of is something to do with your A/C, since the ECU bumps the idle up when it thinks the compressor clutch engages.