Hi guys I am getting a misfire on cylinder 4 I have tried 3 coils and 2 new injectors. The car will run fine for a day or so then go back to missing. Has anyone seen this problem before and if so where do I start in resolving this issue? Any info is appreciated thanks.

 

what kind of spark plugs are you using? using anything other than copper plugs (bosch f8dc4 plugs are oem) might cause problems. when was the last time you changed the spark plugs? interval is every 30-40k miles for your model. did you change the 3 coil to plug connectors (connectors are black rubber and cost around $6/each), they should be changed with every spark plug change to avoid problems.

 

Yes all 6 plugs were changed with bosch super plus plugs 7927 is the number. All new boots and 1 new coil on the # 4 cyl.

 

I have a 96 Mercedez E 320, it was miss firing, I replaced the plugs and cables and still the same, how can I bench test the coils?