I have been looking for answers, swapping parts and I am stumped. Car was missing really bad, thought it was ignition, changed the coil, plugs and wires. Ran fine when cold, then after about 5 minutes starts missing again. Finally got it to quit and not start, no spark. Replaced the distributer (hall sensor) fired it up, missed a few times then sounds great in neutral. Take off in gear and it starts popping again but now it won't quit just doesn't run right. Couldn't hear fuel pump on 1st click, replaced the relay. Still couldn't hear it, replaced in tank pump. Same problem. Getting 10V at pump leads when key is in 1st position then goes to 0v when car is started. Oh, and yes I checked the timing before and after the distributer

 

Finally found one problem which has led to another. CAT was plugged causing the engine to run poorly, ordered and installed the new CAT, short one to two mile test drive and the CAT was glowing bright red. Auto store is getting me a new cat but I have been reading it may not be the CAT but car running rich/lean. The only thing I can think of I havent changed is the O2 sensor. Am I missing something, could it be the ECM? Help please.

 

What do the spark plugs look like?
But yes, you can test the O2 sensor. Running at a "fast idle" (idk; 1200ish rpm?), at operating temperature: If you probe from the backside of the green wire connector with the +lead and ground the - lead of your voltmeter, then the reading should fluctuate between 0 and 1 volt, usually around .5V. If there is no voltage, then replace. If the reading is low, then it's running lean. If the voltage is high, the car is running rich.

 

Thanks so much for the response. When I changed them 1 and 4 looked pretty lean, 2 and 3 looked too rich but not sure if that is an accurate indication with the CAT backed up. Since replacing the CAT I doubt it has ran enough to check the plugs but I will pull them tonight and check.

 

Last evening I have to fix my son's car before I leave town. O2 sensor is good, I did find holes rubbed into intake boot so it has been changed. Gutted the CAT until a new one arrives. Drove it a few miles, stumbles and missed on acceleration and car won't drive above 40MPH. Pulled the plugs ard all are very lean, white. Searches lead me to believe the MAF is the problem. I have cleaned the MAF and when I unplug it the idle is a bit rough which led me to believe it was okay but now I am having second guesses. Before I take it to a mechanic, or spend $ on an un needed MAF what are thoughts on this. I am at the end of my rope. Thanks!

 

Timing too far advanced? CTS?