Strange Afternoon- Cat Converter Fire?

[REVROK]

So I replaced the water pump and radiator in the XJ yesterday and reassembled the jeep, fired it up and it ran fine at first and then started barely operating, so I revved it to see if it would simply clear up. I was leaning over the throttle looking down and see a glow under my XJ. I wonder what is going on? Drop down to look and the cat is cherry red and the undercoating is fully aflame! :flame: I grabbed the hose and put the fire out and cooled off the parts... there appears to be no other damage.

Has anyone else ever had this happen? It definitely ruined an otherwise perfectly good afternoon and scared me... loving that poly gas tank with flames licking at it. Suggestions on a California legal cat? Obviously I'm in the market!

 

[nismo5]

you can get a magnaflow universal cat from autozone,kragan,pepboys for less than $200 and save a few bucks if you or a buddy can weld otherwise i got quoted from $275-$350 to have one installed on my pathfinder

 

[old_man]

The underlying reason the cat was red hot is what you need to worry about. This is commonly a sign of the engine running way too rich.

 

[SeansXJ]

had that happen on my Bronco after the mechanic put my vacuum lines on wrong..i asked him why it was running funny...he stated that its running the way it should and that the previous owner adjusted the timeing to help it run better. long story short i drove maybe 3 blocks to the gas station and when i pulled in the cat was dripping aluminum, same story as yours..but this was in a gas station at the pump..i had to change my shorts after that one.

 

[Alex E]

The underlying reason the cat was red hot is what you need to worry about. This is commonly a sign of the engine running way too rich.

Yeah, its running rich for some reason. Did you touch or leave the engine coolant temp sensor disconnected?

 

[REVROK]

Yeah, its running rich for some reason. Did you touch or leave the engine coolant temp sensor disconnected?

Thanks, that is helpful... as it was burning :bawl: I noticed the short vacuum hose at the back of the intake manifold was disconnected. Since I was working on the cooling system I have no idea how that vacuum hose happened. Pretty frustrating. No to the coolant temp sensor, never disco'd. I will check everything once I get a new cat on it now that I know what to look for.

 

[REVROK]

had that happen on my Bronco after the mechanic put my vacuum lines on wrong..i asked him why it was running funny...he stated that its running the way it should and that the previous owner adjusted the timeing to help it run better. long story short i drove maybe 3 blocks to the gas station and when i pulled in the cat was dripping aluminum, same story as yours..but this was in a gas station at the pump..i had to change my shorts after that one.

Yeah, I understand... mine is 3.5 feet from my house flames probably 4 feet from the wood siding, with my kids inside and flames licking at the plastic gas tank... So very NOT fun. I initially frantically started looking for my extinguisher (in a convenient spot in the garage), but realized the hose was better under the circumstances (and close) with that converter nearly white hot. With the hose right there... definitely better than a gas station!!

I may slap a length of pipe in there since it is my DD, until I have the coin for a cat. I am pretty environmentally conscious though and it will bug me til I get it fixed. Just checked Summit.... Application specific Magnaflow is $144 and Universals are around $60-70

 

[REVROK]

OK... Now I have a new question. If I make the drive to Sparks and, hypothetically speaking of course, get a 49 state Magnaflow for $50 less, will my local smog guy even know the difference? i really don't see how he could??? I am fairly sure there is no emissions difference as there rarely is any rhyme or reason to CARB rules.

 

[Bryan C.]

OK... Now I have a new question. If I make the drive to Sparks and, hypothetically speaking of course, get a 49 state Magnaflow for $50 less, will my local smog guy even know the difference? i really don't see how he could??? I am fairly sure there is no emissions difference as there rarely is any rhyme or reason to CARB rules.

Just because it will pass the visual inspection doesn't mean it will pass the tailpipe test. Another point is an exhaust shop will not install a non-approved cat.

 

[l1kenother]

I talked to my smog guy about getting a 49 state legal cat.. He said not worth it at all. I guess new emission laws are very strict and it definately wont pass smog.

OK... Now I have a new question. If I make the drive to Sparks and, hypothetically speaking of course, get a 49 state Magnaflow for $50 less, will my local smog guy even know the difference? i really don't see how he could??? I am fairly sure there is no emissions difference as there rarely is any rhyme or reason to CARB rules.

 

[REVROK]

I talked to my smog guy about getting a 49 state legal cat.. He said not worth it at all. I guess new emission laws are very strict and it definately wont pass smog.

Oh well... I guess I spend the $50 extra and don't get a free drive to the mountains. As to installing it... easy to put in, doesn't even require welding (which I could do).

 

[old_man]

Before spending the money on the CAT, pull the plugs and do a plug reading. CATs don't overheat by themselves. I have seen a stuck open injector flood one cylinder and pump raw gas into the exhaust and cause a glowing exhaust. The other bad thing this will cause is it will wash the oil from the cylinder walls and leave them scored. Before fixing the results, fix the cause.

Sorry to harp on this if you have already done it, but I just don't like to see an engine ruined when it can be prevented.

 

[kastein]

Check to see if the old one was plugged up... if not, definitely figure out what got it so hot.

My bets - leak in the exhaust system upstream of the O2 sensor, stuck injector, bad CTS, vac leak, lousy spark plugs, etc.

 

[Shorty]

if the vacuum hose on the intake that was disconnected went to the MAP sensor, you would have been running very rich-- it may not have any other underlying problems.

 

[REVROK]

Before spending the money on the CAT, pull the plugs and do a plug reading. CATs don't overheat by themselves. I have seen a stuck open injector flood one cylinder and pump raw gas into the exhaust and cause a glowing exhaust. The other bad thing this will cause is it will wash the oil from the cylinder walls and leave them scored. Before fixing the results, fix the cause.

Sorry to harp on this if you have already done it, but I just don't like to see an engine ruined when it can be prevented.

Good advise guys... believe me I couldn't afford this, let alone any other problems! If you have any other things that have not been mentioned that I should check... keep em comin'! The plan is to make weekend project of fully investigating and THEN replacing the cat.

 

[REVROK]

if the vacuum hose on the intake that was disconnected went to the MAP sensor, you would have been running very rich-- it may not have any other underlying problems.

Where is the MAP sensor? Then I can tell you. Never mind... it's on the firewall in the right general area, I can scope it out when I get home.