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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53943
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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420 sel 1987 missing on idle replaced plug leads and plugs

Customer Question

420 sel 1987 missing on idle replaced plug leads and plugs distributer cap and rotor would ib ecu or idle control unit
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, the ECU and the idle control unit will not cause a misfire at idle. If you have a miss at idle and your ignition system is new the problem will typically be a fault with the fuel distributor or with a fuel injector or a vacuum leak at the manifold or low compression. You should first run a compression test to be sure that you have even compression on all cylinders. Next you will need to identify which cylinder is missing and check for vacuum leaks and swap the injector to another cylinder to see if the misfire moves with the injector. I suspect you will find either an injector is bad or there is a vacuum leak at the manifold or you have a bad fuel distributor.

Let me know if you have any questions. Please be sure to rate my service in order for the website to credit me for helping you.


Expert:  Marty replied 1 year ago.

Hi, I'm just following up with you on this question. I never received credit from the website because you never rated my service. Are you satisfied with my help on this question?