I have a 2001 ML 320 99k miles and my idle has been going down between 500-600 (the tach sits right on top of the 500 line) when the car is on drive and the car starts to shudder when I’m at the stop light. If I put the car on N or P the idle goes up to 800 and the shudder goes away. I have replaced the spark plugs and wires, MAF, and CPS sensor. The shudder gets worst at the stop light if I turn the AC on or when the fan turns on. Does anyone know how to adjust the idle?

 

You should check for codes in the ECM. You could have a prob. with B37.

 

Do you know what is the normal idle speed should be when the car is on D? Thanks Dundee

 

M/B does not supply that info, that I know of.

You ask when it is in Drive but that will take starting a cold eng. and putting in D. And the other one would be after the eng. is at operating Temp.

 

when the engine is warm. I have no issues when engine is cold where the rpm is at 800. When it’s warm it drops to 550 and that’s when I get the shudder. I’m wondering if 550 is normal.

 

I will check on car the next time I go out.

 

Could you please scan for codes.

Try this automatic relearn.

 

i have no codes and I already perform that reset. Thanks Dundee

 

did it work?

 

No. My normal idle speed when in D is still at 550 rpm (warm engine) and my car still shudders at the stop light especially first 3 miles.

I’m going to the mechanic today have the motor and transmission mounts checked.

 

hey Dundee it was the motor mount causing all the shuddering. The mechanic said they are not worn out but rather got hardened and showed my the comparison with the brand new mounts which were softer.

thanks for your help

 

Great info & glad your problem is over.