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Guys, My Truck Is Running Like Pure Crap.


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It threw and engine code last night. I read the code with a code reader. It Shows

 

P0300 Random multiple cylinder misfire detected.

and p0332 knock sensor 2 circuit low input.

 

So I cleared the codes and the truck ran fine until I layed into it and the engine light came back on. This time it read

 

P0101 MAP or VAF CKT range/perf

and

P0300 Random Multiple cylinder misfire detected.

 

I cleared it again, and ran her easy home. Never above 55. I ran it low on gas in case the gas was bad. This morning, I fire it up, let it warm up 5 mins, shoot up the street for gas (91). Filled up, left the parking lot and gave it a bit more gas and the light came back on causing the truck to buck and stutter a bit. When I first looked at the truck it had a little ching ching ching noise under it which I contributed to the exhaust as it was coming from the area where the cat convertors are. Fast forward to 5pm tonight. Truck runs fine, I get on the highway and slowly take the truck up to 55 and it's fine. I set the cruise and run at 55 for 2-3 miles, then gently accelorate up to 70 and reset cruise to stay with the flow of traffic. About 2 miles later, the truck loses forward momentum and the RPMs go up to about 5000. The check engine light is flashing indicating a misfire. The truck begins to buck again like it has a bad miss and throws the check engine light again. I make it to the advanced auto. I opened the door and immediately smelled FOUL FOUL exhaust. I mean it REALLY stunk. I am thinking it's a cat gone bad. My exhaust has 2 mufflers. One for each bank of cyliders and goes out the back at 45s to 2 tips. I put hand over the drivers side tip and can barely feel air movement at all. At the pass side, you can feel it very strong at 18 inches away. I call another buddy in Ohio with an SS (Bowtie70SS) and he says to turn the truck off, let her cool off (the exhaust) and then drive it again. While I am waiting, I rescan the codes and it comes up as

 

P0101 MAF or VAF CKT range/perf

 

P0300 Random/Multiple clylinder misfire detected

 

P0332 Knock sensor 2 Circuit low input (Bank 2)

 

Well I shut the truck down for about 2 hours and then climb back in and start it up, put it in drive. I can instantly tell a different. It's not perfect, but it's alot better. Within 1 mile it's back to being as bad as it was before.

 

 

My question is, do you think that I have a bad cat causing all of this mayhem? If so, will cutting the cats off TEMPORARILY until I get REPLACEMENTS next week make my problems go away and the truck drive normally?

 

I my theory is that the cat is clogged up like an artery, and the engine is cutting spark to several cylinders in order to relieve pressure and protect itself.

 

I could really use your folks help.

 

 

Please please help!

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Yeah it sounds like one of your cats is plugged. You can cut them out temporarily an drive with open exhaust, but you will still throw codes for the two rear O2 sensors. Do NOT let this problem go too much longer, plugged cats have blown engines in the past. FYI, on any GM vehicle when the SES light starts to flash, you are supposed to pull over and turn the engine off immediatly. The flashing light means an active misfire......a lot of times due to a faulty cat like your case, and to continue driving like this will only make the condition worse and could damage your engine in time. :chevy:

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So, it's agreed then. Monday, my truck gets cats removed.

 

 

Anyone else who wants to, please chime in. I'm new to this and am soaking it all in. The more knowledge you folks present me with the better.

 

 

P.S Thanks so much for your time!

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also sounds like a knock sensro is going bad. that will cause timing to be pulled. the p0101 could be a few things.

 

 

I also feel you have multiple issues here. Your second knock sensor (one nearest the "firewall") is having issues. I suspect the sensor is going / gone south and needs replacement or a pinched wire somewhere. They take some time to replace since the entire intake manifold needs to come off. Do you regularly wash your engine? Water is a big contributer to knock sensor corrosion in these LSx motors.

 

I would "fix" / replace your cat converters post haste. This condition will not last too long as your motor will be damaged if you continue to drive it like this. Keep in mind that your cats are under warranty for 80K I believe (as long as you didn't void your warranty) and a trip to the dealer may be in order. :smash:

 

The P0101 MAF code may be resolved with the correction of the two aforementioned issues.

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The driver's cat was the culprit. I cut the off rear of the cat. Fired to truck up and the thing turned cherry red. So, I fixed it :) Truck is load right now until I get that exhaust repaired in the morning. Thank you folks very much for your help, I couldn't have done it with out you.

 

 

P.S. The truck runs like a scalded cat!

Edited by YenkoChevelle69 (see edit history)
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I also feel you have multiple issues here. Your second knock sensor (one nearest the "firewall") is having issues. I suspect the sensor is going / gone south and needs replacement or a pinched wire somewhere. They take some time to replace since the entire intake manifold needs to come off. Do you regularly wash your engine? Water is a big contributer to knock sensor corrosion in these LSx motors.

 

I would "fix" / replace your cat converters post haste. This condition will not last too long as your motor will be damaged if you continue to drive it like this. Keep in mind that your cats are under warranty for 80K I believe (as long as you didn't void your warranty) and a trip to the dealer may be in order. :smash:

 

The P0101 MAF code may be resolved with the correction of the two aforementioned issues.

 

The sensor is getting replaced this coming saturday if all goes well. I do not wash the engine due to fear of something like THIS. And that Cat was SOLID. No wonder the truck didn't run.

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these guys know there stuff

 

I'll say! Thanks again fellas! Went to the exhaust shop today and get the cats repaired :) and other than the crappy droan of the chock masters or whatever mufflers are on there, this this sure runs a heck of alot better. Still throwing the code for knock sensor, along with rear O2s, but I know the fix for that. Thanks again! Hopefully I'll be able to contribute knowledge too soon enough.

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I'll say! Thanks again fellas! Went to the exhaust shop today and get the cats repaired :) and other than the crappy droan of the chock masters or whatever mufflers are on there, this this sure runs a heck of alot better. Still throwing the code for knock sensor, along with rear O2s, but I know the fix for that. Thanks again! Hopefully I'll be able to contribute knowledge too soon enough.

The 332 code means that the computer is not receiving any signal from the rear knock sensor - either it has failed or there is a wire loose. I had the same code, and when I removed the engine cover I found that the connector for the knock sensors had come loose/unplugged! :wtf:

 

Glad you got the cat replaced, but I'd be worried as they rarely go bad for "no reason" - the engine has been running very rich, enough to foul the cat. I would suggest making sure the computer is fueling correctly and your AFR is correct because if it is running pig-rich you'll be fouling cats again. Also is this a nitrous motor? or heavy F/I? Those can also cause cat-killing situations. Also running gasoline above 93-octane... - just thinking out loud...

 

Mr. P.

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Yenko, these guys have given you a ton of GOOD info. PLEASE do the work required to find out what caused this cat to go bad. There have been several members on here that lost their motors due to a bad cat problem.

 

"Now check for damage. Run a compression test pull the plugs take a look at em. Just a double check on the inside of your engine"

Please take this advice to heart and invest the time and $$ to KNOW what the status of your motor is after this major problem.

 

Just trying to save you future grief brother.

 

CD

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