Gen1 3rz cylinder 2 misfire

Need help. Mid December my number 2 cylinder started misfiring. I changed the coil pack problem solved. However it only lasted 30 days then happened again, I changed it a second time. Then yesterday (37 days later) it happened AGAIN. Any help would be greatly appreciated.

 

What brand of coil are you using?

 

Carquest, I replaced all four coils and plug’s about 2.5 years ago. With zero issues till December.

 

Several possible causes. What is the mileage? Have the valve shims been adjusted? Have you done a compression test? If so, what was the compression? Low compression can cause misfire. Out of spec valve shim clearance can contribute to low compression. If compression is low and valve shim clearance is out of spec, an adjustment can improve compression significantly.

Another possible cause is a bad injector.

Both of those problems caused misfires in my 3RZ. Adjusting valve shims and replacing the bad injector fixed it for me. But you should rule out the coils and wires. Doing a compression check would be my next step.

Do you have a CEL or trouble codes?

Edit: If you changed the coil pack twice and its still a problem, I doubt its the coil pack. Check the compression.

 

272000 miles. No on valve shims and no compression test. I do have several CEL Codes (EGR and EVAP emissions).
I understand that a stuck valve/ compression loss or injector can cause a misfire. I don’t understand why changing the coil would fix it albeit temporarily. My feeling is that it would be an electrical issue but not sure where to start.

 

It might not have been the coil. Might just been intermittent somewhat and it only looked like the coil fixed it temporarily. Can't say for sure unless a compression test is done and valves shims are measured. At that mileage, I'd be willing to bet the valve shims are worn and need adjustment. Easy to measure, little more labor intensive to adjust, but can be done on a good weekend. I got mine at 245k miles and the valve shims were very much out of spec. The adjustment resulted in a 30+ increase in PSI in the worst cylinder, which fixed the misfire in that one. I had another intermittent misfire in another cylinder, which turned out to be a bad injector. I didn't realize that was the problem until I sent my injectors off to be serviced.

Worst case you could have a head gasket leak, but lets hope its not that.