W202 1999 C230 kompressor Mysterious misfire on idle

[Munaaf]

Hi guys

Desperate help needed, I have been experiencing a misfire only on idle. When I drive the car seems to be fine.

I have taken it to 2 mechanics who plugged in the scanner but no error codes are found.

Please help !!!

[Vetruck]

Basic 101. When did you last replace plugs? When did you last replace plug wires? IF these are in any question then it is 99% your answer.

[Munaaf]

Basic 101. When did you last replace plugs? When did you last replace plug wires? IF these are in any question then it is 99% your answer.

HI Vetruck

Service was done and spark plugs have been changed. Plug wires have not been changed. Is there a way to test plug wires ? If plug wires are faulty why is the car not picking up any codes ?

[Vetruck]

From my experience (which I could be wrong be doubt it) I have never seen any of my cars ever have codes thrown from a faulty spark plug wire. I can pretty much assure you they are bad. Every time I have ever had a low end miss on any type of car it has always been a plug wire.

edit" Fwiw//(experience wise)- I am almost 50 years old and have owned over 20 vehicles in my life as well as worked on hundreds.

[Munaaf]

Thank you ! I shall try changing them.Is it just the spark plug wire I should change or also the supressor caps ?

One thing that concerns me is that if it is the spark plug wires, should I not feel the mis when the car is been driven or under some load ? as I have said only at idle it is noticeable. While driving I feel nothing. My Milage now is 195 000 Km

[Vetruck]

Energy builds with RPM. A car can run fine at speed yet miss at idle.

[Munaaf]

Thank you ! What I have noticed is that during the time the car mis at idle, the revs do go up a bit ( sort od a hunt then back down )

[Munaaf]

is that normal

[Vetruck]

Yes. That is you car's computer electronic controls compensating to maintain idle. The rpms fluctuate with the miss and as it stumbles the IAC (idle air control) valve opens to simulate throttle application.

[Munaaf]

Thanks a lot for you advice. I will get some ignition wires and try them. will let you know the outcome.

[Abbaso]

HI Vetruck

Service was done and spark plugs have been changed. Plug wires have not been changed. Is there a way to test plug wires ? If plug wires are faulty why is the car not picking up any codes ?

You can test plug wires with a multimeter. Test for resistance. I've only changed plug wires 250 000km.