JC316

I normally hang out in the 4.6L section, but I just picked up a 95 GT. When I first got it, it wouldn't hold idle, was misfiring, and would die after 2 minutes of running, leaving the fan and fuel pump running.

Major vacuum leaks and a bad PCM was causing the majority of the problems, but the misfire remains. It's mostly noticeable at idle, but it definitely feels sluggish on the road. It has a stock H pipe that is open past the cats and it smells pig rich. It has the following new parts:

PCM
Plugs/Wire/Cap/Rotor/Coil.

I have tested the EGR, and even blocked it off to no effect. Timing is set at 10*. TPS voltage is correct. Firing order is correct. All grounds are clean and tight. The only odd thing that I have found is that the distributor cap is very loose, if the clamps are north/south, I can easily rock the cap east/west.

It has no codes, and I am running out of ideas. I will be performing a compression test tomorrow. Any other ideas to look at?

dawson1112

Have you checked the fuel pressure? Maybe the fuel pressure regulator is bad. If the regulator is leaking it can run very rich. Pull the vacuum line off of it and look for indications of fuel in the vacuum line.

You can help the cap being loose by bending the clips slightly so they hold it down tighter.

Are there any leaks in the exhaust before the 02s ? IE, header gasket, header flange. This could cause the ECU to richen the mix because the 02s see the leak as a lean condition and the ECU tries to compensate for it by adding un needed fuel .

You say it has not stored any codes, so I assume you have performed KOEO. Have you also performed a KOER, and cylinder balance tests?

JC316

Fuel pressure is 33 at idle and 43 with the vacuum line off. No signs of the regulator leaking. I will bend the clips, see if it helps. No exhaust leaks. Haven't done the KOER test or cylinder balance test. I did use an IR thermometer to check the exhaust temps, cylinder 7 is running about 100*F cooler than the others, but the plug and compression is fine. Fuel pressure holds, so I don't have a leaky injector.

One thing that I do need to check is the ECT, if it's anything like my old F150, that can REALLY mess with the fuel.

dawson1112

#7 injector may be a little dirty and not atomizing fuel as efficient as the others.
100f doesn't seem too bad, but since your having a miss it does raise a flag.

What did you gap the plugs at? You should be in the ball park of about .054. Its not uncommon though for 1 to get knocked out of spec when installing it.

JC316

I'm not the one that installed the plugs, but when I pulled them, the gap looked a hell of a lot smaller than .054.

Found the source of it running rich, the insulation crumbled on the ECT wires and they were touching. Fixed that and the smell is gone. Still have a miss, but I am resetting the computer now, see if it helps.

JC316

Computer reset didn't help. Started checking all of the sensor wires. Everything else looks OK, but it does have a factory O2 sensor on the passenger bank. Somehow, I don't think it's working properly after 19 years.

pushrods

Try cleaning your MAF. If you have a oiled cotton type air filter it can get contaminated with oil residue and will cause all kinds of air/fuel mixture problems that may not throw codes.

JC316

Forgot to mention that one. MAF is new, replaced by the previous owner. Took it apart just to make sure and it's fine.

JC316

Did yall know that a mustang runs a helluva lot better with the number 4 plug wire actually on the plug? Was fixing to start compression tests when I noticed that number 4 didn't have a wire on it. Runs great now.

dawson1112

LMAO

LMAO

LMAO