Where the coil packs replaced along with the little connectors for the plugs? If not, you may have the coils tested. The plug connectors are cheap and guys here say they are problematic.

My car's wiring harness needs replacing (diagnosed by 2 separate shops) but my check engine light has never come on. You really need to peel some of the insulation back and have a look. I was shocked at how much rot I had with only 79K miles on my '95. With only 86,000 miles, you might still be on your original harness.

OVP is also something to check as mentioned earlier...

-GH

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1992 Mercedes Benz 500SL
1998 BMW 528i
2003 Honda Element
2002 CBR600F4i
1977 Coachmen Motor Home