Catalytic Converter Red Hot

[DavidProehl]

Lately (last couple months) I've felt like my engine has been running hotter than normal. My temp gauge looks good so I thought I might be imagining things. Today I looked at the cat and it was glowing red. That indicates I'm running rich right? My oil sensor light wire runs right by there and it melted the wire a bit, enough such that now my oil light is on.

A few months back I replaced plugs, wires, cap, & rotor (more like I had a lot of help), it wouldn't surprise me if something got messed up when doing the plugs, we had to slide the mixture control unit to get at everything, maybe the gasket under there is no longer forming a seal? What else could be causing this?

[David T]

If you didn't touch the mixture screw you are probably misfiring on one or more cylinders. Raw fuel is getting to the converter and burning in it. I would be checking the ignition wires and spark plugs. Pull the plugs and see if they are all nice and tan. If one is black then you found the cylinder that is not firing.
David Teitelbaum

[DavidProehl]

Thanks for the suggestion. The mixture screw has not been touched. I'll start by checking the plugs.

[Dangermouse]

Or your cat is partially plugged/disintegrated ?

[Bitsyncmaster]

Is your frequency valve still buzzing?

[Joe Kuchan]

Another option is to use a non-contact IR thermometer to check the temp of the exhaust manifold at each cylinder. A rich (or non-firing) cylinder will be colder than the others, while a lean cylinder will probably be hotter.

[dmc6960]

Bring it back to my place, I'll warranty my work!

[DavidProehl]

Bring it back to my place, I'll warranty my work!

Jim, my intent is certainly not to point fingers! I greatly appreciate the help you gave, no chance I could have done that on my own. That said, if you are interested in taking another look at it, I'm in!


Is your frequency valve still buzzing?

Good thought. I just fired it up, and yes, it is buzzing.

Ok, I should have used the multi-quote feature. Sorry for the triple post.


Or your cat is partially plugged/disintegrated ?

Maybe after heating up the way it has! I'd have to remove it in order to verify that right?

[Bitsyncmaster]

Ok, I should have used the multi-quote feature. Sorry for the triple post.



Maybe after heating up the way it has! I'd have to remove it in order to verify that right?

You may have melted some of the core but at idle you probably have enough still open to find and fix the problem with it running hot. It still could be something has gone bad with the mixture. Do you have a dwell meter?

[delornut]

If you didn't touch the mixture screw you are probably misfiring on one or more cylinders. Raw fuel is getting to the converter and burning in it. I would be checking the ignition wires and spark plugs. Pull the plugs and see if they are all nice and tan. If one is black then you found the cylinder that is not firing.
David Teitelbaum

Running extremly lean will cause the cat to glow as well. Large vacuum leak maybe??? When the mixture unit was moved I'd guess the pipe from the idle motor was removed. When the pipe was replaced the 'o' ring sealing the tube to the mixture unit may have been upset which would cause a pretty large vacuum leak. The gaskets sealing the 'W' section at the rear of the intake manifold could leak as well because this was part of the area dis-assembled. The flexable rubber area between the throttle plates and the mixture unit could have been torn. You'd notice the car running bad in either a rich or lean condition that would be exteme enough to cause the cat to glow red. Spaying something around suspected vacuum leaks will momentarily cause the engine speed to change if there is a leak. I normaly used an unlite propane tourch or starting fluid but with a glowing cat I'd stick with water in a spray bottle. That would still affect the way the engine runs for just a few seconds as the fluid gets sucked into the intake.

Bruce Benson

[sean]

Running extremly lean will cause the cat to glow as well. Large vacuum leak maybe???.
Yup, had the same issue. Lean situation and glowing cat.

[DavidProehl]

You may have melted some of the core but at idle you probably have enough still open to find and fix the problem with it running hot. It still could be something has gone bad with the mixture. Do you have a dwell meter?

No dwell meter. Jim offered to help, he likely has one. He seems to have everything.


Running extremly lean will cause the cat to glow as well. Large vacuum leak maybe??? When the mixture unit was moved I'd guess the pipe from the idle motor was removed. When the pipe was replaced the 'o' ring sealing the tube to the mixture unit may have been upset which would cause a pretty large vacuum leak. The gaskets sealing the 'W' section at the rear of the intake manifold could leak as well because this was part of the area dis-assembled. The flexable rubber area between the throttle plates and the mixture unit could have been torn. You'd notice the car running bad in either a rich or lean condition that would be exteme enough to cause the cat to glow red. Spaying something around suspected vacuum leaks will momentarily cause the engine speed to change if there is a leak. I normaly used an unlite propane tourch or starting fluid but with a glowing cat I'd stick with water in a spray bottle. That would still affect the way the engine runs for just a few seconds as the fluid gets sucked into the intake.

Bruce Benson

Thanks Bruce, so your saying if I spray water around there, it may get sucked in and cause a brief rough idle. I'll have to give that a try. Might be worth ordering all new gaskets as well just to be safe. To me this makes the most sense since all connections were triple checked on the wires before reassembling. We knew there would be a potential issue with the seals since those were original to the car as far as I know.

[delornut]

No dwell meter. Jim offered to help, he likely has one. He seems to have everything.



Thanks Bruce, so your saying if I spray water around there, it may get sucked in and cause a brief rough idle. I'll have to give that a try. Might be worth ordering all new gaskets as well just to be safe. To me this makes the most sense since all connections were triple checked on the wires before reassembling. We knew there would be a potential issue with the seals since those were original to the car as far as I know.

Anything sucked into the intake other than a proper fuel mix will alter the engines running for a few seconds. Using an ignitable product like starting fluid will cause the idle to speed up for a second or two if it finds a way into the intake via a vacuum leak. If you're carefull to stay well away of the glowing cat that would be the best indicator. Water would probably cause a brief stumble when sucked into the intake. I have a digital dwell meter but I was there when you guys did the tune up and you didn't alter anything in regards to air/fuel ratios other than having the possibility of a vacuum leak because of what was dis-assembled and re-assembled. I'd like to give you and Jim a hand but I'll be pretty busy all week and out of town for part of it. One other area to check that just came to mind is to make sure no injectors were knocked loose. If they're not clipped down and sealed that could also be a pretty significant vacuum leak.

Bruce

[DavidProehl]

Anything sucked into the intake other than a proper fuel mix will alter the engines running for a few seconds. Using an ignitable product like starting fluid will cause the idle to speed up for a second or two if it finds a way into the intake via a vacuum leak. If you're carefull to stay well away of the glowing cat that would be the best indicator. Water would probably cause a brief stumble when sucked into the intake. I have a digital dwell meter but I was there when you guys did the tune up and you didn't alter anything in regards to air/fuel ratios other than having the possibility of a vacuum leak because of what was dis-assembled and re-assembled. I'd like to give you and Jim a hand but I'll be pretty busy all week and out of town for part of it. One other area to check that just came to mind is to make sure no injectors were knocked loose. If they're not clipped down and sealed that could also be a pretty significant vacuum leak.

Bruce


I appreciate the advice. I may as well order all my gaskets/'o' rings prior to meeting up with Jim just in case they are needed. You mentioned a couple:

W-pipe gaskets: http://www.delorean.com/store/p-6436-intake-manifold-gaskets-pair.aspx

'o' ring for this pipe: http://www.delorean.com/store/p-6739-auxiliary-air-pipe.aspx
I didn't see the 'o' ring associated with this. Do you have a part number?

Any other gaskets/'o' rings I should have on hand just in case? I'd rather spend a few extra bucks to have the parts on hand than to realize we need it and be unable to do anything about it.

[delornut]

I appreciate the advice. I may as well order all my gaskets/'o' rings prior to meeting up with Jim just in case they are needed. You mentioned a couple:

W-pipe gaskets: http://www.delorean.com/store/p-6436-intake-manifold-gaskets-pair.aspx

'o' ring for this pipe: http://www.delorean.com/store/p-6739-auxiliary-air-pipe.aspx
I didn't see the 'o' ring associated with this. Do you have a part number?

Any other gaskets/'o' rings I should have on hand just in case? I'd rather spend a few extra bucks to have the parts on hand than to realize we need it and be unable to do anything about it.



This is the "O"ring. It's held in place by a brass cup that presses into the mixture unit
housing.
SKU:102293 $2.66

The brass cup has a price listing of zero which I assume means they don't have them.

[Nicholas R]

Yup, had the same issue. Lean situation and glowing cat.

+1

Same thing happened to me from clogged injectors. In fact I've never heard of a car getting hotter because of running rich. Less oxygen would in fact cause it to run a bit cooler. I remember when Cliff S. was driving his EFI car in a parade and his radiator fans weren't working so he intentionally richened the mixture and turned the heater on to make it through the parade.