Are you talking about the catalytic converter?

I had the car checked professionally, hooked to a computer and everything, and had the entire fuel system roto rootered (flushed out).....even after this the check engine light came on after the flushout.

After everything I've done it can be only one of three things going bad since I've covered everything else in the list.

# Faulty spark plug or wire - Wires and plugs are good to go
# Faulty coil (pack) - Coil pack is brand spanking new
# Faulty oxygen sensor(s) - Both sensors are new, less than 15K on them
# Faulty fuel injector
# Burned exhaust valve
# Faulty catalytic converter(s)
# Poor compression - Compression is good

I've heard that there are more than two oxygen sensors in the Mustang V6 aside from the two that are under the drivers side and passenger side. Where is the third one located at so I can check it and see if that is the problem?

I don't think it's the fuel injector since I've had the system flushed out twice in the last year by a professional.

So it's either the burnt exhaust valve, or the catalytic converter....I have noticed a rotten egg smell when the car is running in the garage.

 

Actually in most mustangs, at least mine anyway, there are four(4) oxygen sensors. 2 of them are pre-cat, on either side, 2 of them are post-cat on either side. Basically there's one before and after each catalytic converter. Trust me though, check that egr position sensor.

 

What year is your car, does it smell gasy out the exhaust? Flashing CEL, low power?

 

Don't drive it in limp mode!!

 

2000 Mustang V6.

Since the fuel system cleaning the car runs a lot better, the CEL came back on after clearing but it runs better than it did before, and the CEL doesn't flash anymore. The CEL only flashed every few days.

I'm thinking it's the injector or maybe the O2 sensor..I'm going to check to see if there are two more O2 sensors pre-cat and if so swap them out and see if that makes any difference.