Gen III Caught on Fire - Possibly Catalytic Converter

[johnnyk_6]

I was out doing some spirited driving with a buddy the other night when I noticed smoke coming from the driver's side wheel well at a stoplight. I quickly pulled off onto a service road where we hopped out to look for the source of the smoke. We didn't find anything obvious in the engine bay, but when my buddy looked under the car he saw a small fire that appeared to be near the catalytic converter on the driver side.

I ran around the area frantically trying to find someone with water or a fire extinguisher while my buddy called the fire department. Fortunately, there happened to be a police officer nearby who had a fire extinguisher in his cruiser. The fire appeared to be in the hole near the front-driver-side jack point, so that's where I aimed the extinguisher and was able to put out the fire.

I called a tow truck and had the car towed home, then jacked it up to try and locate the source of the fire. I found what appeared to be some kind of heat shielding around the exhaust/cat bracket that had melted:

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My guess is that the catalytic converter plugged up and started running hot enough to melt/ignite some nearby components. Does anybody have advice on how I could confirm that the catalytic converter is the cause? I haven't had the car towed to Woodhouse yet because I'm afraid I won't be able to find an OEM cat, so I'd ideally like to confirm that it's the cat and look around for the part myself before towing it and having the car sit in a lot for potentially weeks or month while I wait to find one.

If it is in fact the catalytic converter, then this would indicate some other underlying problem that's causing my cats to fail. I had to replace a plugged cat last year within the first 3k miles of ownership (around 22k miles on the car when it failed). My theory is that the car came with a tune on it because it makes exhaust pops which I don't think are from a stock tune. I'm guessing a previous owner ran catless with a pop tune, then threw the cats back on before selling it, so I've been running a pop tune that smoked both of my cats.

So I'm curious if I can check for signs of a bad cat myself before having the car towed to the shop and potentially waiting weeks for a replacement cat. I'd also like to know the best way to go about checking for a tune. Any insight or advice would be greatly appreciated!

[Martyb]

It almost looks like copper wire inside the heat shield, never seen that. If the cat was clogged I would think you would have noticed as my bet would be it was running less than optimal. Just my 2 cents. Glad it didn’t burn!

[13COBRA]

Just take it in. Even if it's a catalytic converter, just put high flows in, you'll be happy you did.

[Viper98]

johnnyk 6, put hi flow cats on. There are other places, local, so you don’t have to take it to Woodhouse. Mark Jorgensen, out at Bentley, doesn’t do that type of work, but there are other shops that can help. Extreme down on 132/L St can do it. I had mine done by them. I have a Gen 2.
The Gen 3 guys can tell you if are any codes or whatever after install. I didn’t have any CELs.
We don’t have emissions here or any inspections so you can make changes. Just keep the old exhaust just in case.

[johnnyk_6]

It almost looks like copper wire inside the heat shield, never seen that. If the cat was clogged I would think you would have noticed as my bet would be it was running less than optimal. Just my 2 cents. Glad it didn’t burn!

When I previously had a plugged cat, the car had noticeable power loss and hesitation for several days and eventually threw a code. I didn't notice any performance decrease while driving before it caught fire so I wonder if it could be something else?

[Viper98]

Woodhouse will leave your car outside like the common Neon while waiting for parts. Extreme and others will pull your car inside.

[johnnyk_6]

Just take it in. Even if it's a catalytic converter, just put high flows in, you'll be happy you did.

This is definitely an option I am considering - maybe cheaper in the long run than replacing OEM cats.


johnnyk 6, put hi flow cats on. There are other places, local, so you don’t have to take it to Woodhouse. Mark Jorgensen, out at Bentley, doesn’t do that type of work, but there are other shops that can help. Extreme down on 132/L St can do it. I had mine done by them. I have a Gen 2.
The Gen 3 guys can tell you if are any codes or whatever after install. I didn’t have any CELs.
We don’t have emissions here or any inspections so you can make changes. Just keep the old exhaust just in case.

I will probably go with hi-flow cats if it turns out to be the stock catalytic converter. I will check out Extreme and look around for some hi-flow cats in the likely case I go with that option. Thanks for the recommendation!

[johnnyk_6]

Woodhouse will leave your car outside like the common Neon while waiting for parts. Extreme and others will pull your car inside.

That's exactly what I am afraid of. Don't want to tow it there and leave it outside for weeks, or have to tow it home again and back once the part comes in (Woodhouse is an hour away so a flatbed tow isn't cheap).

[13COBRA]

If I were closer, I'd help out. My shop is 25 minutes NE of Kansas City.

[Viper98]

I suggest you purchase the hi-flow cats, once received make an appointment with the shop and have it towed once. Mike Moss, at Extreme, is an artist. He is very meticulous.

[1Willy1]

Glad it's ok , could of been so much worse

If it was my car id order two high flow cats and have a reputable exhaust shop weld them in same day

Is there any reason we would need a viper specialist for a simple cat install ?

[Mbccenter]

I purchased a gen 3 that had a cat fire. Car was running so rich on the one side that it put extra fuel in the cat. I figured I would just have to replace o2 sensor and be done. I was wrong. Took forever to figure out what was going on. Turned out to be a knock sensor. Computer can not read them on the gen 3 and they can do some crazy stuff to the tune. Funny thing was the car was pretty fast when it had the issue but slowed down once fixed.

[Viper Specialty]

Can you further explain what you found?

We have pretty good access to G3 knock sensing parameters, and they have always served us well.

However... one thing I have seen more than once is knock sensor wiring being zapped by old plug wires and damaging the PCM and/or knock inputs.

[johnnyk_6]

After taking the side sills off, it appears the heat shielding above the secondary cat burned through to the fiberglass layer.

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It looks like the rubber exhaust isolator piece is what caught on fire.

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So I'm fairly certain it's the secondary cat that failed. I guess it's time to look for some hi-flow cats :D

[johnnyk_6]

I purchased a gen 3 that had a cat fire. Car was running so rich on the one side that it put extra fuel in the cat. I figured I would just have to replace o2 sensor and be done. I was wrong. Took forever to figure out what was going on. Turned out to be a knock sensor. Computer can not read them on the gen 3 and they can do some crazy stuff to the tune. Funny thing was the car was pretty fast when it had the issue but slowed down once fixed.

How did you diagnose the knock sensor issue? Were there any other symptoms that could indicate this being the cause?

[JonB ~ PartsRack]

Cats dont plug themselves.something Up-stream is fouling the cat

Plugs, wires, coils, oxy sensors, and more, and now KNOCK sensors!?!

Dont just replace the cats without finding and fixing the fouler or you are doomed to chapter-2


ps we can offer HF, and OE used cats: JonB@PartsRack.com

Thanks and good luck

[johnnyk_6]

Cats dont plug themselves.something Up-stream is fouling the cat

Plugs, wires, coils, oxy sensors, and more, and now KNOCK sensors!?!

Dont just replace the cats without finding and fixing the fouler or you are doomed to chapter-2


ps we have HF, and OE used cats JonB@PartsRack.com Thanks and good luck


I will take it to Woodhouse to see if they can't figure out what's plugging up the cats. Hoping it's just a pop tune that's dumping fuel into the cats. Regardless, I will be reaching out about some new HF cats. Thanks JonB!

[Scott Mannny]

Cats dont plug themselves.something Up-stream is fouling the cat

Plugs, wires, coils, oxy sensors, and more, and now KNOCK sensors!?!

Dont just replace the cats without finding and fixing the fouler or you are doomed to chapter-2


ps we can offer HF, and OE used cats: JonB@PartsRack.com

Thanks and good luck

Jon B is the place to go, he'll have the parts to you QUICK!!! He has helped me so much, I don't go anywhere else.

[RT SERPENT]

Jon B is the place to go, he'll have the parts to you QUICK!!! He has helped me so much, I don't go anywhere else.

:t1236: ... What he said :)

[JonB ~ PartsRack]

Used OE cats and rubber bracket in a UPS box, shipping tomorrow to get you driving....
HF cats ship in 5-6 weeks.

Thanks

Thanks Manny and Serpent for the kind words.......

[RCR88]

Fred at the Blair store is great to deal with. Very knowledgeable.

[johnnyk_6]

JonB got me set up with some high-flow cats, and an OEM to tie me over until those ship. Thanks so much for your help JonB!

[Garron]

I will take it to Woodhouse to see if they can't figure out what's plugging up the cats. Hoping it's just a pop tune that's dumping fuel into the cats. Regardless, I will be reaching out about some new HF cats. Thanks JonB!

I repaired several Gen 3 cars that would repeatedly go through cats. It was almost always a cracked factory shorty header. There is an oxygen sensor in the header when the inside bracing cracks the oxygen sensor will read lean the computer dumps extra fuel until the cat plugs.

This is very easy to smoke test through the exhaust pipe and check. Do not just install cats you will have the same problem in 1500 miles.

On a lot of Ontario cars we would just install the full Belanger system because with the expense of the cats and manifolds you are almost at the same cost.

Good luck

[SRT_BluByU]

You could have a bad injector on that bank uf this is the second converter on that side.. maybe running extreme rich. Could be washing cyl down also. Oil smell like fuel?

[johnnyk_6]

I repaired several Gen 3 cars that would repeatedly go through cats. It was almost always a cracked factory shorty header. There is an oxygen sensor in the header when the inside bracing cracks the oxygen sensor will read lean the computer dumps extra fuel until the cat plugs.

This is very easy to smoke test through the exhaust pipe and check. Do not just install cats you will have the same problem in 1500 miles.

On a lot of Ontario cars we would just install the full Belanger system because with the expense of the cats and manifolds you are almost at the same cost.

Good luck

I will ask the shop to check for this - thanks a lot for the info.


You could have a bad injector on that bank uf this is the second converter on that side.. maybe running extreme rich. Could be washing cyl down also. Oil smell like fuel?

Oil doesn't seem to smell like fuel. The previous cat that failed was on the passenger side, so now cats have failed on both sides. Will ask the shop to check all injectors regardless. Thanks!

[johnnyk_6]

A friend and I have been doing some troubleshooting on the car while I wait to get it serviced at Woodhouse next week. At this point, we've pretty much ruled out the catalytic converter.

The first theory I had was a plugged cat. Jon B helped me out and shipped an OEM replacement while I wait for the high-flows that I ordered.

Once that arrived, a buddy and I took off the old cat to look for damage but couldn't find anything obvious. Before putting the new OEM on, I used a borescope to look at the catalyst material inside each one. Here's what they looked like:

Original cat:
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The replacement:
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We put the replacement on and fired up the car. Within about a minute we started to see smoke coming from the replacement cat. I looked around with a flashlight and saw smoke coming from near the flex pipe. At this point I realized the same issue is still happening and it probably isn't the catalytic converter.

Next, we checked the O2 sensors with a multimeter. Both pre-cat and post-cat sensors have continuity. Then we fired up the car and used an OBD scanner to confirm that they are working fine.

While running the OBD test, my friend used a socket extension as a redneck stethoscope to listen to each injector. Each injector seemed to be opening and closing just fine. We also used the multimeter to check if each injector had continuity, which they all did.

The only remaining thing I could think of was the spark plug wires. The plugs were replaced about a year ago so we didn't bother to pull them out. We did however check the inside of each of the rubber boots and found one that appeared to be damaged. I stuck a borescope in each of the boots to get a closer look and here's what I found:

The damaged one:
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What the other ones look like:
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So at this point, I'm pretty sure it's a bad spark plug wire. My current theory is that one cylinder isn't getting spark so unburnt fuel is being dumped into the exhaust, either burning up and superheating the cat, or causing the O2 sensor to run that side extremely lean and causing excessive heat. It hasn't thrown a code yet, but I haven't ran it for more than a couple minutes at a time.

Could a bad spark plug boot/wire be causing the cat to get hot enough to the point that it smokes or catches something on fire? Any input is appreciated.

[usmcfieldmp]

The smoke on first start up is most likely just the oils and such burning off. If you put your bare hands all over the exhaust pipe or catalytic converter, it'll smoke a bit when you start it back up. Plus factory/manufacturing oils, etc.

Have you pulled and checked your spark plugs and read them? https://ngksparkplugs.com/en/resources/read-spark-plug

If it does actually have a pop/crackle tune on it, then that is definitely your problem as those will destroy catalytic converters. Definitely check all other avenues before assuming this is the case.

Simply running pig rich will also clog them. This was a common issue with the early Cobalt SS's when I bought mine in 2006. From the factory it was running around a 10.2:1 AFR at WOT. Ridiculously rich.

[GTS Dean]

First, check for bad plug boots and obvious signs of damaged ignition cables. If those look good, open the hood and run the engine in the garage with the door open at night with no lights on. Use a spray bottle to mist the wires with Windex or soapy water and look for sparks. I found that my 20+ year old Magnecor wires which looked perfect in every way were arcing trough pinholes on multiple cables. Gen 3-5 engines have much shorter wires than Gen 1&2.

[johnnyk_6]

First, check for bad plug boots and obvious signs of damaged ignition cables. If those look good, open the hood and run the engine in the garage with the door open at night with no lights on. Use a spray bottle to mist the wires with Windex or soapy water and look for sparks. I found that my 20+ year old Magnecor wires which looked perfect in every way were arcing trough pinholes on multiple cables. Gen 3-5 engines have much shorter wires than Gen 1&2.

Thanks for the tip. I checked all of the plug boots last night and found one that looks damaged on the inside compared to all of the other ones. Since the issue doesn't appear to be a catalytic converter, O2 sensors, or fuel injectors, I'm thinking it has to be the plug wire. I'm ordering a new set of ignition cables today. Will post another update once I get them installed.

[ViperSRT]

If you have arcing down the plug ceramic you may have to replace both plug and wire at the same time. Visible by a carbon track either on the plug ceramic or the inside of the boot.

[Johnny ViperBro]

It almost looks like copper wire inside the heat shield, never seen that. If the cat was clogged I would think you would have noticed as my bet would be it was running less than optimal. Just my 2 cents. Glad it didn’t burn!

Correct. I had a clogged Cat that had to be replaced ($2200). Car ran like a slug and smelled like unburned gas in the cockpit.

[JonB ~ PartsRack]

Correct. I had a clogged Cat that had to be replaced ($2200). Car ran like a slug and smelled like unburned gas in the cockpit.


YIKES ! ONE clogged cat for $2200? Did that include repairing whatever caused the un-burned fuel clog?



FYI, HiFlow cats for the entire car cost about 35% of that, and offer several driveability benefits.