Extreme Missfiring and Red Hot Cat

[S-lime]

So my car started running terribly a while ago, bucking under full throttle, shaking, loss of power.. I ran it through vagcom and the only codes present were low input to MAF and missfires you all four cylinders. So I unplugged the MAF as recommended by an online forum. That completely fixed the problem and the car ran amazing.. Until today. It started running so rough it was barely even drivable, the entire car was shakin horrendously and when I opened the hood the catalytic converter was glowing red hot.. Tried plugging my MAF back in with no luck.. What's going on??

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It has only been running with the MAF unplugged for a day prior while my new one is on order.

[xdewaynex]

Sounds like you have a clogged catalytic converter.

[redline380]

Yeah, cat could be bad. But if unplugging the MAF helped, you could have fueling issues too.

Either way, if the cat was glowing, it is most likely shot. I would start there.

[ECS Tuning-Audi]

I wouldn't necessarily deem the cat shot after it has been running while missing very badly. Un-burnt fuel from the misfiring makes its way out the exhaust ports and into the cat where it eventually burns which creates more heat. Thus causing the cat to glow.

This is why they do not recommend that you drive your vehicle if it's misfiring badly or your check engine light is flashing.

Start with the basics, check your plugs and coils. Your MAF may need cleaned or replaced. Do the easy/cost effective things first before you start throwing parts at it.

Good luck!

Jason

[redline380]

I wouldn't necessarily deem the cat shot after it has been running while missing very badly. Un-burnt fuel from the misfiring makes its way out the exhaust ports and into the cat where it eventually burns which creates more heat. Thus causing the cat to glow.

That's exactly why I think the cat is plugged. Unburn fuel makes its way to the cat, where it burns and causes the catalyst to melt and plug up, thus restricting flow of exhaust and causes massive back pressure.

[ECS Tuning-Audi]

That's exactly why I think the cat is plugged. Unburn fuel makes its way to the cat, where it burns and causes the catalyst to melt and plug up, thus restricting flow of exhaust and causes massive back pressure.

Definitely not out of the question. Though it seems that the glowing cat just started happening because of the misfires. If its not something that has gone on for a long period of time I would think the cat is OK. Extensive driving while misfiring will definitely cause havoc to the cat so I'd avoid driving it as much as possible until its fixed.

Replacing the cat can get expensive unless you go aftermarket/used. I'd rather try the simple/cost effective possible fixes first. Then if you are still experiencing the issue pull the cat off an inspect it then replace it if needed.

Jason

[Davdraco1]

Buy a test pipe and use it for its original purpose. If the car runs fine, bad cat, if it still runs like crap, then check the other stuff. I think the eBay test pipes work well and you might have an issue with the o2 sensor location but for 65 bucks why not.

[S-lime]

Replaced cat with with a test pipe today.. No change

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Update: replaced catalytic converter with a test pipe today. Problem persists.

[Davdraco1]

If it still runs like hell then the cat was not clogged. Are you throwing any codes?

[S-lime]

Yes, Missfiring on all 4 cylinders.

[Davdraco1]

Like Jason said, start with the plugs and work you way backwards thru the ignition system. What engine code is it? Do you have an ICM?

[nemick]

I saw this just once and it turned out to be bad plugs. Exactly the same symptoms.