So I have a friend with a 99 Tacoma and we have been chasing a misfire in cylinders 3 and 6 for awhile now. When his truck first started having issues he had a knock sensor code. We fixed that but then two days later he got codes P0300 P0303 and P0306. Spark plugs are newer, wires are brand new and we've moved the coil pack around to see if we'd get a different cylinder misfire but it stayed in cylinders 3 and 6. Starting to run out of ideas of what could be causing this. What else can I check. Possibly ecm? How could I check that? any help would be appreciated.

 

Fuel injectors?? compression test?? Back to basics.

 

Would bad compression or injector cause a miss in two cylinders tho? I mean yeah the idea has crossed my mind but it seems highly unlikely to get bad compression in two separate cylinders at the same time, or have 2 injectors go at the same time. Was already planning on doing the compression test soon.

 

Whenever you have eliminated the impossible, whatever remains, however improbable, must be the truth.

How many miles on this 20 year old truck??

 

It could be the low tension (12V) coil wiring. I'd still be sniffing around the ignition side of things, based on the cylinder pairing.

When you pull the #6 wire, put a plug in it, rest the plug against metal, does it spark or not? It's hard to test the coil-on-plug side of the motor, but the plug wire side is easy.