misfire with bad exhaust - Toyota 4Runner Forum

Previologist · 10-30-2023, 11:45 AM

apparently a misfire can be caused by bad exhaust. Does anyone have experience with this, and did fixing the exhaust fix the misfire? My muffler has been getting progressively worse and now I'm getting rough running and a misfire code. I'm hoping I haven't burnt a valve or something. I'm scheduled to get the exhaust fixed tomorrow but if I have more serious problems maybe I shouldn't bother.

Of course the misfire could be completely unrelated

Jungoes · 10-30-2023, 11:54 AM

I just replaced a ruptured muffler ( after I was running a straight pipe installed after my Catalytic convertor was stolen) no misfire issues when it happened .
All repaired now with new cat and muffler.

My misfire issue that came up once was a bad plug wire on one of the coil packs, the terminal inside the wire attaching to the head terminal in the coil pack was bad, replaced wires and misfire eliminated.

Previologist · 10-30-2023, 05:14 PM

Quote:

Originally Posted by Jungoes

I just replaced a ruptured muffler ( after I was running a straight pipe installed after my Catalytic convertor was stolen) no misfire issues when it happened . .

I also have experience with misfires caused by other things, but I'm wondering about misfires caused by leaky exhaust

Previologist · 11-07-2023, 04:44 PM

It appears that fixing my exhaust fixed my misfiring, so now there is someone here with that experience.

gamefreakgc · 11-07-2023, 06:01 PM

I could see that if the exhaust was either plugged or if the issue is upstream of one of the O2 sensors. Glad you got it sorted out.

Previologist · 11-10-2023, 12:41 AM

Maybe. The CEL came back on and I haven't pulled the code yet. It was running great but I may have detected a misfire

The O2 sensor had lost its nuts and was just wobbling around and leaking. But I never pulled an O2 code before the exhaust repairs, just misfire code

gamefreakgc · 11-11-2023, 06:57 PM

Quote:

Originally Posted by Previologist

Maybe. The CEL came back on and I haven't pulled the code yet. It was running great but I may have detected a misfire

The O2 sensor had lost its nuts and was just wobbling around and leaking. But I never pulled an O2 code before the exhaust repairs, just misfire code

It wouldn't throw an O2 code, it would throw a P0171 lean code. The O2 is one of two sensors that controls fuel flow and is vital that it is airtight.

Previologist · 11-12-2023, 11:22 AM

Quote:

Originally Posted by gamefreakgc

It wouldn't throw an O2 code, it would throw a P0171 lean code. The O2 is one of two sensors that controls fuel flow and is vital that it is airtight.

Well it didn't throw that code either and it was so loose you could pull it out.

Vehicle ran fine yesterday after clearing the misfire code, so I'll just have to keep an eye on it

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