I went to the junkyard and got a distributor (with pickup coil), an igniter and another TPS. None of these fixed the misfire.

Any other suggestions would be appreciated. At this point I am not sure if it is fuel or spark related. Any tests that will lead me down the right path?

On a whim I decided to check the O2 sensor. Its a brand new bosch sensor. I attached a meter and saw an output from the sensor usually about 100mv and occasionally dropping to about 40mv or so. So I took it for a 2 mile test drive with the O2 sensor disconnected and it ran the same as if it was connected.....ie I still had the misfire/stumbling/hestitation. And upon my return I checked the codes and there was still no code for the O2 sensor.

Now I am quite confused. I expected there to be huge difference between running with and without the O2 sensor. And I also expected a code to be generated.

Any help would be appreciated.

Thanks,
Gregg

Problem solved.

Ditch the Bosch sensor, and order an OEM sensor (Denso). The probe on the Bosch is too short to reach into the exhaust stream, so the ECU can't go by those readings.

Well, we've gotta help Gregg out here a little.

www.sparkplugs.com will be a bit cheaper on your wallet.

Also, check out how the feedback loop works in the emissions tech articles here:

www.autoshop101.com Definitely worth bookmarking.

what about upgrading to a heated oxygen sensor? It seems as though even an OEM Oxygen sensor (single wire) would not work well at idle or light load conditions as it might not get hot enough. Plus its worth mentioning that I have headers (with 2.5" pipe, 2.5" cat and 2.5" muffler) so the Oxygen sensor is sitting back near the cat rather than on the exhaust manifold.

Any thoughts?

Update.....I had an extra heated O2 sensor from a different application. I bench checked it and it appears good. I checked it once installed and it appears to work good.

But I still have a miss at idle.....and a slight stumble on acceleration. I am going to readjust the throttle position sensor on Saturday and see if that helps.

The misfire/stumble is not all that bad but I am a perfectionist of sorts. I figure this motor should idle and run with no misfires at all. Is this a reasonable goal?

Sounds like a burnt valve too me. Stick a rag over the exhaust while the engines idling. When you hear a miss keep an eye on the rag. if it sucks into the exhaust a little while misfiring it means theres a burnt valve.

This was a trick a mechanic mate taught me, and I haven used it for a while so my memory is a little hazy. But I?m 99% sure.

I am showing good compression on all 4 cylinders so I dont think its a valve.