MIS FIRES ON 1 AND 6

I have a 2001 toyota 4runner. Months ago I had a misfire on cyl 3. I ended up replacing all plugs and coils and problem was solved. 5 k miles later same thing. I swapped coils and still cyl 3. I checked compression on cylinders and they are 150 psi on 1,2,4,6 3,5 are 145. I replaced the injectors and tested for vacuum leak with smoke test. Now I have a misfire on 1 and 6. I am wondering if catalytic converter might be bad. Any other ideas on why I'm misfiring. New.coils, plugs wires, and injectors. I'm lost

 

All Toyota or Toyota OEM Supplier replacement parts? Cheap aftermarket injectors or coils often cause issues and rework. Toyota coils almost never go bad.

I wouldn't think the cat would cause a misfire without first cause an overall degradation in power.

Next up would be to swap injectors.

Does the misfire seem to be present throughout the RPM range?

 

Misfires can be caused by fuel pump problems/fuel delivery. Bad sensors, or failing emissions control stuff. It’s possible you’ve got a coil that’s failed. Moving it around might help isolate the issue or not. Also, is there something installed that might obstruct airflow near that coil? Heat kills coils too.

Have you scanned for codes or used a diagnostic tool to better diagnose the problem?

 

I can almost guarantee it’s the plug wires arching to the head. You should be able to see where if you pull the caps off the plugs.

 

the boots can arc down in the hole too. one more hiding place...

 

I recently bought a 1999 4Runner V6. The guy I bought it from had a similar problem with the car. He replaced the coil on the mis-firing cylinder. It still had the miss. Then he put in new spark plug cables, and it runs great. I'm enjoying the 4Runner and it runs smooth as glass.