I have a 94 Civic VX that has a mis at around 2k RPM. It has around 150k miles on it and was running fine before this. It is a commuter car so it has seen a lot of miles in the last year. I have replaced the following trying to get rid of the mis, rotor, cap, plugs with correct NGKs, wires, Denso o2 Sensor, and fuel filter. When the car starts to hesitate you can give it throttle and the mis goes away and speed up like normal. It is not the lean burn mode because it will have multiple hesitations and not the single going in and out of lean burn. Any recommendations? Thank you.

 

Any CEL codes?

 

No codes, not even an engine light. The problem stops when the o2 sensor is disconnected, which is why I bought a new one. It did't fix it. It has sometimes had trouble starting at the first of the day also, but not all the time.

 

Does the CEL work?

Have you measured the fuel pressure and tested the FPR?

 

The CEL light does work. It will come on when the o2 sensor is unhooked. I have not checked the fuel pressure yet.

 

The CEL light has not come on, but I thought I would check to see if any codes were stored in the computer while I was checking out some sensors. I did check the MAP sensor and it responded to vac and also checked the TPS and it seemed fine. There was a fault code "5" stored in the computer. Even though the MAP sensor checked out fine, I bought a new one to just make sure. After installing the new one, the car still has the mis. I still have not checked the fuel pressure as I do not have the valve to screw into the fuel filter top to check the psi. Any more suggestions with the fault code 5 and a good MAP sensor? I do not hear any vacuum leaks either.