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Popping out exhaust when going slow/slowing down, rough idle...

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New User

Aug 4, 2019, 3:12 PM

Post #1 of 2 (2368 views)
Popping out exhaust when going slow/slowing down, rough idle... Sign In

Sierra /c 3500 (regular wheel drive, non-dually)
168,xxx miles

Popping out exhaust when going slow, running rough.
Changed plugs, wires, cleaned maf sensor, added new muffler, deleted rear cat cause i was told it might be clogged ( previous owner deleted O2 sensors in the rear so I figured it wouldn't matter if I deleted that cat temporarily).
Had a shop tell me its a burnt valve, trying to make sure before I pull the trigger on a 1500 - $2,000 repair.
It's also throwing a PO174 code, however that happened after I clean the mass airflow sensor so I might have triggered it? Engine light comes on for a while and then it goes away. I'm tired of throwing money at this thing, can't afford to get it wrong anymore. Help?
And here's the weird thing - it was running beautifully a few weeks ago as I was going down the highway at 65-70 mph and then all of a sudden it started acting up, so I pulled over and there's a board in between the cab and bed of my truck laying on the exhaust smoldering and what appears to be a piece of trash stuck to my exhaust area on fire! The symptoms sprung up at the time of this fire... Maybe a coincidence? I don't know.
A cop happened to be nearby and sprayed a fire extinguisher on it. And down the road I went with the exhaust popping and running rough.
Any suggestions?

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Aug 4, 2019, 3:41 PM

Post #2 of 2 (2355 views)
Re: Popping out exhaust when going slow/slowing down, rough idle... Sign In

You don't have to ask us if it has a burnt valve. There are plenty of tests that can confirm that.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

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