Hello, I have a 99 Civic/auto with a misfire issue. Ive researched relevant threads on this topic and tried most of the fixes, but no result. I was hoping perhaps someone here could give me some fresh ideas.

The car starts fine, but there's an intermittent stumble in the idle about every 15-20 seconds. When you drive it, it hesitates/stumbles off-idle and you can feel it misfiring/hesitating a little bit at cruise. When you accelerate it stumbles before it downshifts and pulls away...once you get past that stumble, it pulls OK - until you settle into a cruise speed and you feel that little hesitation again. Sometimes, from rest, it stumbles severely but I can usually feather the throttle and get it past that. Once in awhile it will stumble enough to die, but it always cranks right back up.

Codes are:

1. O2 sensor #1 bank
2. Cat converter efficiency below normal #1
3. MAP sensor
4. IAC valve
5. Cyl #1 misfire
6. Cyl #2 misfire
7. Cyl #3 misfire
8. Cyl #4 misfire

I have:

1. Replaced plug wires
2. Cleaned IAC valve
3. Cleaned throttle body
4. Verified injector firing
5. Replaced distributor
6. Verified spark to plugs
7. Checked timing
8. Replaced fuel filter
9. Replaced O2 sensors

The timing belt was replaced about 5k ago.

Nothing's helped. Any ideas out there? Its extremely frustrating.

Thanks!!

 

Are you still getting the CEL codes for the cat, IAC valve, and MAP sensor? Did the distributor include a new ICM and coil? Did you replace the rotor and cap as well?

 

Dont know about the CEL, I'll have to go back to the autoparts place to get them read again. Distributor had a new ICM and coil, but no cap/rotor. I will try replacing them next.

Thanks

 

Here's an example of what a cap in good shape looks like. (I recently checked mine.)



If yours looks similar, you may not need to replace it.

 

Update: replaced cap and rotor, which made a significant improvement; no hesitation so far. Hopefully, its fixed!