Mercedes-Benz Forum banner

Idle Problem That Fixed Itself.........almost.

4672 Views 141 Replies 6 Participants Last post by  LauraS
Today on my way into town I stopped at a stoplight which was red and the engine ideal wandered up rom about 500 to 750 RPM and seemed to have an ignition miss or something. I was a bit worried that it would stall but it didn't and once I accelerated the engine ran fine. This happened about 5 times when I had to wait for red lights. The temperature gauge read 90C and the ambient was about 22C. When I got to my destination I left the car for about 1 hour and when I returned the car sputtered but did start and settled into a nice 600RPM idle and from then on all of the way home it ran just fine? I have no idea what happened. Does anyone have any suggestions ? I would like to know of maybe the ICV might have been sticking or something else to look at.
1 - 1 of 142 Posts
Sputtering or hard starts after it was warm might be indication of either a leaking injector (or several) or a failing fuel accumulator unable to keep up the rest pressure in the fuel system.

Idle issues could range from a vacuum leak, dirty/faulty ICV, fuel mixture issue from the EHA, or the small microswitch at the throttle body. These cars didn't have the idle control modules like the bigger V8 cars had, so that's one electronic gizmo that you don't need to worry about. Could be a fouled plug, improperly gapped plug, bad plug wires, or buildup up the cap and rotor.

Although it solved itself, it's quite possible it will return again. There's just a host of things that could be responsible or contributing to the conditions your described. Check the basic things like plugs and wires, cap and rotor, then start looking visually at any vacuum lines or air hoses for obvious cracks and other damage. If all that checks out, then it may be time to dive deeper into the CIS system and measure things such as the duty cycle to make sure the fuel system is actually functioning properly.
See less See more
1 - 1 of 142 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.