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93 4.0 exhaust running red hot
- Thread starter poomero
- Start date
Jeep Driver
NAXJA Forum User
- Location
- Parrottsville
Clogged cat.............other than that....IDK
Dragonlich1961
NAXJA Forum User
- Location
- Ohio
like he said a clogged cat, or you are running stupidly pig rich. either way, don't drive it more than absolutely necessary, that cat is a fire waiting to happen, and it will probably take your truck with it if not careful.
clydefrog
NAXJA Forum User
- Location
- Northern California
Where is it hot? The whole exhaust or just a section. More info would help, although it sounds like you have a clog somewhere. Why did it need a cat? Maybe there is another problem that took out the first cat (running rich).
jeepingben
NAXJA Forum User
- Location
- Maine
A clogged injector caused this on my 95 YJ.
You say new manifold? Any leaks? If air gets in, the O2 sensor sees it as lean and the PCM will add fuel. The extra fuel will make the cat work harder.
You say new manifold? Any leaks? If air gets in, the O2 sensor sees it as lean and the PCM will add fuel. The extra fuel will make the cat work harder.
Needed a CAT so the shop would work on it. I dont know if that was true or not but they put one on it. The CAT is running red nothing else.
ParadiseXJ
NAXJA Forum User
- Location
- Paradise, CA 95969
The cat is likely the hottest spot on the whole vehicle, which it is supposed to be, to burn off excess fuel/emissions that got by the engine. On all the cats I've installed there is an arrow to indicate flow direction. Don't know if that makes a difference, but may be worth looking under there.
If it didn't have a cat, the shop either can't or won't work on it to avoid liability (or they may just say that) as it's illegal to remove a cat if it came with one from the factory (federal law) and/or do work on an illegal vehicle. Just sayin'
If it didn't have a cat, the shop either can't or won't work on it to avoid liability (or they may just say that) as it's illegal to remove a cat if it came with one from the factory (federal law) and/or do work on an illegal vehicle. Just sayin'
Jeep Driver
NAXJA Forum User
- Location
- Parrottsville
Get that POS off there........if what you are saying is true? red hot? Get rid of it.
Find a different shop.
- Location
- Southern Maryland
exhaust leak will cause air to get sucked in, making o2 sensor think the engine is running lean, resulting in the computer dumping fuel to balance it out. The excess fuel burns off in the exhaust, making it super hot
- Location
- Waukegan, IL
If it's just the cat getting red hot, I'd lean towards the fuel system being extremely rich. If its the manifold, then I'd suspect a lean condition,(vacuum leak, clogged injector, bad o2.)
1)Check tune up first, excessive spark gaps can ship unburnt fuel down stream.
2)Check O2 sensor, they can skew lean over time and cause excess fuel delivery
1)Check tune up first, excessive spark gaps can ship unburnt fuel down stream.
2)Check O2 sensor, they can skew lean over time and cause excess fuel delivery
Jeep Driver
NAXJA Forum User
- Location
- Parrottsville
Lean = hot. Rich = cool.
How is it you had such a leak and not figured that out immediately?
- Location
- Southern Maryland
Lean will make the engine hot, rich will make the exhaust hot
- Location
- Golden, CO
Good job!
Back in the '90s, I used a company truck that the carburetor started dumping excessive fuel down the intake. I did not notice any problem until one night I saw an orange glow under the truck. That excess fuel was burning off in the muffler.
- Location
- MilkyWay Galaxy
X2!!!! Precisely correct. But lets call it rich=cool, extra rich or late timing= glowing in the dark hot.
The other poster was correct too, just left out the middle area detail.
With a dead CAT, and dead O2 sensor they run a little rich and cooler.
Lean enough the engine will overheat and other bad things happen....
Rich with a new CAT may over heat the CAT, rich enough it will make the CAT glow also. Late ignition or leaking exhaust valve, or sticking injector can make the exhaust manifold glow before it gets the CAT. Assuming no pre CATs.
- Location
- MilkyWay Galaxy
If it was running rich, that burned up/out the old Cat, and will do it again very fast if you do not fix the excess fuel problem.
- Location
- MilkyWay Galaxy
Yes and no, the extra fuel simply takes the jeep back to stoich to match the extra air IF it is a leak into the intake. The excess air and fuel still go through combustion cylinders and just boosts the rpms-power, IF it is a leak into the Exhaust, I can see that, yes.
- Location
- MilkyWay Galaxy
OK. Then somebody explain to me blow by blow how an intake leak can make it run rich if all else is working?
HUGE leak by passing the MAP or IAT and screwing with fuel calcs? Or a screwed up O2 sensor as well as a leak and other things? Or the leak was too close to the MAP sensor Vac line?
I'm just buying a simple intake leak only can do that. Gotta something else going on there I think.
- Location
- MilkyWay Galaxy
I had a 73 Ford LTD burn up 2 exhaust manifold gaskets in days. Then one night I popped the hood and the exh manifold was cherry red
Turned out the Vacuum advance on the Dizzy was rusted and not moving. The spark was too late and a lot of the fuel was still burning when the exh valves opened.
I also had a no start from 1 gallon of gasoline in the engine oil, 78 Dodge V-8. The Carb float stuck open and flooded the oil pan with fuel while I drained 2 batteries cranking and testing it..... The old style fuel pumps ran off the cam shaft and would rupture the diaphragm and dump fuel into the oil too. Had that happen twice as I recall.