a6 c5 misfire issues

[singerj95]

heres a rundown on the things that lead up to my current situation of my car sitting in the parking lot not able to move under its own power..
First started out with a pretty bad misfire when i was home for thanksgiving, that turned into an intermittent one for a couple weeks, my mechanic at home looked at it and couldn't replicate what i was feeling.
Drove back to school, and put in new spark plugs, wires, and coils thinking that was the first thing that could be the issue. And it worked, for two weeks.
I was coming back one day pulling into school, and the car has a bad misfire again, shaking the car with the CEL blinking, so i park it and schedule it to get looked at in 2 days. I assume i can drive it the 3 miles to the shop without a tow. On the way the misfire isn't as noticeable when moving faster (higher revs). I come to a stop and notice my car is smoking, the insulation around the passenger side cat is on fire. Call the police and fire, and they put it out, get towed the last mile to the shop. They said it was the cat being clogged that caused the misfires, and that also made it heat up too much.
Is this reasonable? Or could it be something else, and the misfire killed the cat?
Not sure where to go from here. Help would be appreciated.
last checked these were the codes it was throwing
p0300
p0301
p0306
p1432
p0113
I was also having intermittent connection/ bad catalyst sensor on bank 2, the one that caught fire. Even though i spaced them out.

If i cant figure this out as definite im going to just sell the car, because i cant afford 2 new cats, and then have the car still not run

[PaperToast]

need more info about the car; year, engine code, mileage, recent work . . .

[singerj95]

need more info about the car; year, engine code, mileage, recent work . . .

A6 c5 1999 with 161k. Codes are above. Those are the only that we're read

[chris86vw]

They said it was the cat being clogged that caused the misfires, and that also made it heat up too much.
Is this reasonable? Or could it be something else, and the misfire killed the cat?


misfires could damage a cat causing it to clog causing it to overheat causing it to catch fire

Or a clogged cat could cause misfires causing it to burn off the fuel in the exhaust causing it to get hot causing it to catch fire.

Kind of hard to say, this is a chicken or the egg situation.

Your P1432 code could be a kombi valve stuck open, or a result of it thinking that was the problem and this was it's best guess as there is no sensor on the kombi valve, maybe the solenoid is stuck.

A suck open combi valve could be introducing air to the exhaust when it doesn't need to be, then with a misfire fuel that didn't burn in your cylinder is now burning in the exhaust just like it is designed to do but only on cold starts to get the cats up to temp more quickly. If this is occuring all the time then this could have overheated the cats, causing them to fail and created the misfire.

the P0113 is high intake temps. This could be due to the cats being clogged and running hot, it could be form the misfires causing excess under hood temps, it could be that kombi valve being open routing hot air back into the intake raising actual combustion temps.. causing misfires.

No matter what on this car and any car you ever own again you need to put your 02 sensors where they should be, I really hope you mean you spaced out the post cat sensors.. even then this is the answer to no question ever asked. This likely didn't cause any problems unless you spaced the fronts out, but it certainly did not help by telling the car the wrong information especially since you had cats. Just say no to 02 spacers.


Really this is a complicated issue further complicated by the fire that no one here can do anything but guess. Personally I would temporarily gut the cats since they are bad anyway, fix any damage from the fire and see what happens. If it is fine, and you check the kombi valves etc to be functioning right then the cats may have been the cause and then replacing them should be fine. If you are still having problems with the car with the cats gutted then you'll need to evaluate if repairing that problem and installing new cats will be worth it to you.

[singerj95]

Thanks for the help. I'll try that and see if it works. I think the combi valve sensor went off because I had unplugged the sensor. But I'll look at that too

[nochance9]

I would also replace ICM's for good measure. I got the China made ones from Amazon and they have worked fine for me.

Good luck!

[PaperToast]

I would also replace ICM's for good measure. I got the China made ones from Amazon and they have worked fine for me.

Good luck!
i have a set with about 50k on them, they are typically good for 150k +/-

[singerj95]

pretty sure my car doesnt have ICM's, '99 a6 c5 avant. i think those were on the next model, or the 2.7t
Going to bring it into the shop next month when im back at school. its going to have to sit her until then...