Glowing Cat????

[Crankshaft]

My son has an 88GT with a magnaflow X with hi-flow cats, BBK shorty headers and magnaflow mufflers. After it ran for about 10 minutes, I heard this popping noise from under the car and an extreme amount of heat. When I looked underneath, I noticed the cat on the passenger side was glowing red. The driver's side looked fine. What the hell would cause the cat to glow red? On the net, I've read everything from running lean, to running rich, to a bad spark plug or spark plug wire could cause this. I figured since you guys are the fox body gurus, you may have experienced this problem yourselves and could point me in the right direction.


Any Clues???? :wtf:

[Shane361]

Posted it up elsewhere, will relay all replies. Not sure myself why you would be sending that much heat out of the engine on the passenger side though.-Shane

[Crankshaft]

Thanks man! It's a weird one for sure

[Crankshaft]

The more I read about this, I'm learning that a misfire, being from a bad plug, or a bad wire can cause raw fuel to dump into the exhaust and then ignite once it hits the cat. Guess the next step is to replace the wires and plugs.

[Masshole]

im not sure myself.... but maybe a bad x-pipe??? like something in it like a... squirell. :lmao: i know my first thought would be to take it off and check it.

[Shane361]

Well I would def start with replacing the spark plugs with a good properly gapped set. Then if it is still happening and if possible on that car swap the plugs to the driver side and see if the issue moves over with it. Before all that how is the pressure at the exhaust from one pipe to the other? Maybe that cat is clogged and heat is building but not sure about that one. -Shane

[Dirty_SOHC]

It will run like sh^t if the cat is clogged. It is more than likely running lean, it has to be running rediculously rich to cause that, usually running a little rich will actually keep the cats cool. Pull the plugs on that bank and see what they look like, look for signs of detonation and also let us know what color they are, if possible get some close up pics for us.

[Shane361]

Some replies from SVTPerformance..

I had this happen once to an 88GT I owned years ago.... it turned out the 10 pin connector at the back of the intake had a bad connection.

I've only seen it a few times (never in a Mustang) and it was always either a plugged cat or a rich condition where the extra fuel was igniting in the exhaust, and the fire couldn't get through the cat so that's where it made camp. After which, the cat was usually toasted. With a V8, I'm not sure what would cause one side and not the other... but I'd start with cobra186's experience at this point.

I would say plugged or running rich, but I would say plugged and check that first.
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[Fox87]

What's a cat? Haaaa, none of my stangs (except my Cobra) have seen a catalytic converter since they did away w/emissions.

Good luck on solving the problem.

[fordracing89]

My votes on toasted catalytic convertor as well.

[Cruehead]

Most likely a clogged cat, Dave.

[Crankshaft]

Okay...update time. I haven't had much time to mess with the car due to my son graduating boot camp (yay!). Anyway, I pulled the plugs, and OH DAMN! 2 of the plugs had no gap.. .yes, I said no gap. (both on the passenger side). The other 6 plugs were gapped at .040 and Autolite recommends .052 to .054. After replacing all the plugs with the right gap, the idle problems, and hesitation went bye-bye and the Cat is back to normal. It's starting to act like 5.0 should. Anyway.. thanks for the input. Take care. :mick:

[Masshole]

Okay...update time. I haven't had much time to mess with the car due to my son graduating boot camp (yay!). Anyway, I pulled the plugs, and OH DAMN! 2 of the plugs had no gap.. .yes, I said no gap. (both on the passenger side). The other 6 plugs were gapped at .040 and Autolite recommends .052 to .054. After replacing all the plugs with the right gap, the idle problems, and hesitation went bye-bye and the Cat is back to normal. It's starting to act like 5.0 should. Anyway.. thanks for the input. Take care. :mick:

thats awesome :mick: glad it wasnt a big problem :blkvnm:

[Shane361]

Lost #3 to a no gap plug a month ago. It seems 90% of the time..it's the plugs. I change them out atleast every 6 months now and check them every three.-Shane

[TT_GT]

A glowing catalytic converter is failing due to too much fuel. Take it to a qualified shop, tell them you likely need a new catalytic converter (unless this problem is new) and ask them to find out why it's running rich. If you don't fix it soon you may end up burning the car down..not kidding

[TT_GT]

The Cat probably needs to be pulled from the exhaust system and examined to see if the catalyst has bridged inside. That means that the catalyst material has been running so hot from an overload of fuel or some other contaminants that it blocks the exhaust flow. (Hence the glowing red) The catalyst inside looks like it has been welded together. Only fix for this is a new one.
If this one is bad you need to see what made it run so rich.

[Crankshaft]

The Cat probably needs to be pulled from the exhaust system and examined to see if the catalyst has bridged inside. That means that the catalyst material has been running so hot from an overload of fuel or some other contaminants that it blocks the exhaust flow. (Hence the glowing red) The catalyst inside looks like it has been welded together. Only fix for this is a new one.
If this one is bad you need to see what made it run so rich.


Thanks... I did find the problem to be 2 non gapped plugs, and the other 6 were not gapped enough. After replacement, the car is running awesome. Just glad I caught it before it ruined the cat.

[Crankshaft]

Lost #3 to a no gap plug a month ago. It seems 90% of the time..it's the plugs. I change them out atleast every 6 months now and check them every three.-Shane


Yeah... I appreciate your help on this Shane... your advice was right on!

[my86gt]

congrats on finding the problem