Quote:
Originally Posted by Sugar Bear
Replace the spark plugs. If the check engine light continues replace the coils on 6 & 7 or swap the coils to other cylinders to see if the misfire follows the coil.
Fuel of different octanes have different ignition characteristics. My guess is that 6 & 7 have weak/marginal ignition that just squeak by on the burn characteristic of premium/higher octane. Run the proper octane from a top-tier brand in the car.
No I don't think it is injector related although 14,000 miles of regular has not been keeping them as clean as premium.
Good luck!!!
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Yes - I finally got to doing this test. Switched the coil packs between #5 and #7.
Magic - the CEL reported that the misfires (from P0307 to P0305) moved from #7 to #5.
I think we have the root cause.
Thanks so much for your patience.
Comment: I have changed the spark plugs and the wires, but missed changing the coil packs.
So - replacing the coil packs now is fair.
Suggestion to All Reading this. Changing the coil packs when you change the plugs (I was penny wise pound foolish)
This is a M113.940 engine, Model: E430 Year: 2002