Bouncing Idle when car is on "P"
 

Hello everyone,
Last week my car (1995 C-280) began to give me problems:
1. When I turn the car on the idle bounces anywhere from 4-14 RPM. When I put it on "D" everything is fine, however, when I come to a stop, the idle goes down and back up (it does this with and without the a/c).
2. When I step on the gas, the car waits about 2 seconds to respond, then it mis fires and finally accelerates poorly.
Both of these problems began at the same time. Any help will begreatly appreciated. Thanks in advance.:D
Regards,
Inky

Could it be fuel pressure? or air meter? NOTE: the "check engine" light is NOT on!

Usually, this osrt of thing can be traced to a vacuum leak.
The idle stabilizer circuit is going outside of its parameters attemting to maintain your idle.
Check out all air hoses and clamps and even things like the dipstick, oil filler cap, and vacuum lines.
After you have determined that *no* air leaks are present,
then you check any fuel pressure regulating functions, and temperature sensors.

Sounds like the MAF (Mass Air Flow) sensor. MAF failure is a common failure on the M104 engines... sounds like this is probably your problem.

It does not bounce in D, but only in P, correct? Test Neutral, it should bounce in that too, I believe. The MAF is the wire connector that attaches to the air intake between the engine block and the air filter.

You can try twisting/unplugging the sensor with the car in Park and see if it makes a difference...

Good luck!

Thanks for the replies. Although it's been a long time I still have the problem. I will check the vaccum line as well as the air sensor. How can I know if it is the air sensor?:rolleyes:

Mass Airflow Sensor will probably trig a "check engine" light.

Ok. Let me clarify... The "check engine" light is NOT on. Basically the problem is when I accelerate the car. When I accelerate fast the car does not respond quick and misfires several times. However, if I accelerate very slowly everything is fine.

I'm getting the same thing but my check engine light is on. p0170 is the reading. I know it could be the MAS and stuff...I'm just trying to make sense of the live reading i'm getting to make sure that it is.