Why Are My Catalitic Converters Glowing Red Hot

[steveb44]

1991 LS400

Car has no power and is misfiring

I have recently changed both ignition coils and the spark plugs, and have changed the cats.

Perhaps I should do the LAMBDA sensors?

[The-Acre]

1991 LS400

Car has no power and is misfiring

I have recently changed both ignition coils and the spark plugs, and have changed the cats.

Perhaps I should do the LAMBDA sensors?

Well you've just described my recent grief but mine was a coil. Have you checked the HT leads very carefully. Did you buy new coils or used ones and have you tested them again? Just because they were changed recently doesn't mean they still work.

Welcome to LOC by the way.

[Thunderchild]

I would suggest that the cats are glowing red hot because you are spewing unburt fuel into them and it's burning there and as a result you cats are now destroyed.

The loss of power could be related to this in that the internals have probably worked loose and are blocking the exhaust. Not a good place to be mate!!

HTH

Tc

[itarumaa]

In my old Volvo s40 the problem was in the coil, so I would start to investigate this option first.

And yes, you will destroy the cats, I did that in my Volvo as well.

If you want to shortcut, then just leave the cats in place without internals and hope it will past the emission test, for 1991 car that could be a possibility.

[steveb44]

thanks for the replies. Can someone tell me the best way to test the coils they are new ones but as mentioned thats no guarantee I guess

[Mybikesacx500]

thanks for the replies. Can someone tell me the best way to test the coils they are new ones but as mentioned thats no guarantee I guess

I had a bad coil, running rough, and red hot cats. If one coil is bad, removing the ht lead doesnt affect the engine running, as it's not working anyway, ie, if the left hand coil is bad and you disconnect it, the car will start and run the same as when it was connected, wheras if the right hand coil is faulty, disconecting the left hand coil will mean the car wont start at all.

There is also a resistance mesurement test, my faulty one was out of spec.

[steve2006]

If you find the coils are OK ( where did you buy then from btw?) have you condidered the distributor caps and rotor arms?

A good test for the coils is to remove the coil leads one at a time where it connects to its distributor then hold the conductor close to but not touching the engine or bodywork ( wear gloves!) then get some one to crank over the engine while you look for a good spark jumping across the gap if it is a good strong spark it would suggest the coil is OK if you don't get any spark suspect the coil even though it is new.

Also start the car in the dark and look for electrical arcing which would indicate a HT leak from the coils or spark plug leads.

[sir john]

I had a similar problem over a year ago. The cats were stinking hot. I changed the disi caps and roto arms and it cured the problem.

Good luck mate.

PS; the disi caps and rotas were juct £32 delivered so not expensive.

[steveb44]

Thanks for posts. Turned out to be a coil that was changed only a few month ago so I had assumed it was ok. The car is running spot on now.

I am hoping cats will be ok has I have only run the car 2 miles with them on and with dodgy coil.

[itarumaa]

You will have to be extra unlucky to have problems with the cats considering how short distance you did drive,

so I would not worry

[The-Acre]

Thanks for posts. Turned out to be a coil that was changed only a few month ago so I had assumed it was ok. The car is running spot on now.

I am hoping cats will be ok has I have only run the car 2 miles with them on and with dodgy coil.

Glad you got it sorted. I only ran mine for about a mile, and although it seems to be running fine there's a sound from underneath that wasn't there before. When it's cold and I rev the engine I hear a kind of tinny sound. So if anyone can shed some light on that it would be appreciated.

[steve2006]

Thanks for posts. Turned out to be a coil that was changed only a few month ago so I had assumed it was ok. The car is running spot on now.

I am hoping cats will be ok has I have only run the car 2 miles with them on and with dodgy coil.

Glad you got it sorted. I only ran mine for about a mile, and although it seems to be running fine there's a sound from underneath that wasn't there before. When it's cold and I rev the engine I hear a kind of tinny sound. So if anyone can shed some light on that it would be appreciated.

Check the heat shields around the cats and Y pipe the overheating may have caused the fastenings to break also have a look at the rear box shields the metal rusts and they fall off the bolts and end up sitting on top of the exhaust boxes.

[The-Acre]

Thanks for posts. Turned out to be a coil that was changed only a few month ago so I had assumed it was ok. The car is running spot on now.

I am hoping cats will be ok has I have only run the car 2 miles with them on and with dodgy coil.

Glad you got it sorted. I only ran mine for about a mile, and although it seems to be running fine there's a sound from underneath that wasn't there before. When it's cold and I rev the engine I hear a kind of tinny sound. So if anyone can shed some light on that it would be appreciated.

Check the heat shields around the cats and Y pipe the overheating may have caused the fastenings to break also have a look at the rear box shields the metal rusts and they fall off the bolts and end up sitting on top of the exhaust boxes.

Ta, I guess I need to get it up in the air. it's certainly not the rear shields, they were done some time ago and the sound is coming from the front.