3.4 l cylinder 6 misfire-suggestions please

99 Taco 3.4L, 184,000 miles. INTERMITTENT cylinder 6 misfire. This is not a daily driver but running errands today. Running smooth and strong until after 1st stop. Had gone about 10 miles, 20 minutes driving time, mostly 35-45 MPH, stopped for about 10 minutes, started up to leave and running rough. Had OBD in the truck with me, hooked it up and got P0306, cylinder 6 misfire. No choice but to drive home after one more stop. CEL came on shortly after, later went out, but running rough-obvious misfire all the way home. This has been going on a while. Truck sits for a few days starts up and runs well (usually) until a stop and restart when misfire begins. Not sayin' it doesn't sometimes happen from the get-go, or after driving a while without a stop, but that's the pattern I've noticed mostly. Recent spark plug and wire change. I've also swapped the ignition coil packs and the misfire remails only with cylinder 6. Suggestions please! Puzzled that this is intermittent, or occurs after truck has run fine for a while then happens after warmed up fully, stop and restart. TIA

 

Likely an injector if you've got relatively new plugs and coils/wires. But the first step here is swapping the plug and see if it follows, etc.. then the coil, and then the injector. Or you could just try some injector cleaner and cross your fingers.

 

Has your coolant even gotten low?

 

This was on a 4.0L, but I had similar behavior after a plug change. One of the new plugs had a hairline crack that was impossible to see until it was used for a bit. Swapped the plug and it was fine.

 

Leak down and compression test

 

I'll second whomever suggested that it might be the injector. I wonder if you also get a P0300...

If you decide to replace the injector, I'd suggest that you call MotorWest in Canoga Park, CA and ask about their rebuilt injectors. I'd also recommend replacing all six of them, given the mileage on your engine.

 

Sounds exactly like my symptoms, except mine is cylinder 5. https://www.tacomaworld.com/threads/po305-cylinder-5-misfire-solved.775365/
Swapped coil packs and plugs. Misfire did not follow. Swapped injectors and misfire followed. I ordered a set of these: https://motorwestperformance.com/product/upgrade-for-23250-62040/
They arrived in today’s mail, they shipped quick, and I’m going to put them in tomorrow.

 

248000 miles and injectors are still good.

I recommend this stuff. https://www.royalpurple.com/product/max-clean-fuel-system-cleaner/

 

Update on my original post re P0306 misfire. I ordered and installed 6 new injectors from Motorwest. Problem solved! I got both a Chiltons and Haynes from my local library but neither were nearly as helpful as 2 excellent Youtubes I found, one from Timmy the Toolman and the other from RustBucketProductions. I highly recommend both Youtubes for anyone with modest skills (like me) taking on this job. Also, service from Motorwest was excellent.