C6 Backfiring while accelerating
Thread Starter
Intermediate
Joined: Sep 2015
Posts: 33
Likes: 1
C6 Backfiring while accelerating
Well my first run at the track Saturday night kinda sucked. Wasted 30 min cause they couldn't get things in order with my car number.
It's a stock 2008 c6 M6 Z51 NPP gutted cats
Then it does a gun shot of a back fire while doing a burnout people start yelling shot gun.... Going down the track it backfired several times. On takeoff there was a bit of a bog I launched at 2500 guess I needed a higher rpm, then it did a small screach and hooked.
I tried adhering to rangers advice on launching it. I gutted my cats the other day and wonder if now I need tuning.
.6573 reaction
2.1971. 60ft
5.7739 330ft
8.6403. 1/8 et
86.79. 1/8mph
11.05. 1000 et
13.0971 1/4 mile et
112.61. 1/4 mile Mph
Any thoughts guys?
https://youtu.be/N55CIJMVHzA
Here's a link to my run. It's been 3 years since I last ran a car at the track. So I'm trying to get back in the groove. This back fire issue needs to be resolved.
Thanks in advance for any advice
It's a stock 2008 c6 M6 Z51 NPP gutted cats
Then it does a gun shot of a back fire while doing a burnout people start yelling shot gun.... Going down the track it backfired several times. On takeoff there was a bit of a bog I launched at 2500 guess I needed a higher rpm, then it did a small screach and hooked.
I tried adhering to rangers advice on launching it. I gutted my cats the other day and wonder if now I need tuning.
.6573 reaction
2.1971. 60ft
5.7739 330ft
8.6403. 1/8 et
86.79. 1/8mph
11.05. 1000 et
13.0971 1/4 mile et
112.61. 1/4 mile Mph
Any thoughts guys?
https://youtu.be/N55CIJMVHzA
Here's a link to my run. It's been 3 years since I last ran a car at the track. So I'm trying to get back in the groove. This back fire issue needs to be resolved.
Thanks in advance for any advice
Last edited by Magnvox; Sep 21, 2015 at 07:39 PM.
Drifting
Joined: Apr 2006
Posts: 1,278
Likes: 2
From: Lexington TN. Retired Navy
Well my first run at the track Saturday night kinda sucked. Wasted 30 min cause they couldn't get things in order with my car number.
It's a stock 2008 c6 M6 Z51 NPP gutted cats
Then it does a gun shot of a back fire while doing a burnout people start yelling shot gun.... Going down the track it backfired several times. On takeoff there was a bit of a bog I launched at 2500 guess I needed a higher rpm, then it did a small screach and hooked.
I tried adhering to rangers advice on launching it. I gutted my cats the other day and wonder if now I need tuning.
.6573 reaction
2.1971. 60ft
5.7739 330ft
8.6403. 1/8 et
86.79. 1/8mph
11.05. 1000 et
13.0971 1/4 mile et
112.61. 1/4 mile Mph
Any thoughts guys?
https://youtu.be/N55CIJMVHzA
Here's a link to my run. It's been 3 years since I last ran a car at the track. So I'm trying to get back in the groove. This back fire issue needs to be resolved.
Thanks in advance for any advice
It's a stock 2008 c6 M6 Z51 NPP gutted cats
Then it does a gun shot of a back fire while doing a burnout people start yelling shot gun.... Going down the track it backfired several times. On takeoff there was a bit of a bog I launched at 2500 guess I needed a higher rpm, then it did a small screach and hooked.
I tried adhering to rangers advice on launching it. I gutted my cats the other day and wonder if now I need tuning.
.6573 reaction
2.1971. 60ft
5.7739 330ft
8.6403. 1/8 et
86.79. 1/8mph
11.05. 1000 et
13.0971 1/4 mile et
112.61. 1/4 mile Mph
Any thoughts guys?
https://youtu.be/N55CIJMVHzA
Here's a link to my run. It's been 3 years since I last ran a car at the track. So I'm trying to get back in the groove. This back fire issue needs to be resolved.
Thanks in advance for any advice
Why are the cats gutted? is that causing it to throw a code? may need a tune just for that.
How many miles on the car?
what octane gas were you running at the track?
is this the first time is back fired on ya?
Was it cutting out, or miss firing going down the track or even the hwy for that matter?
Thread Starter
Intermediate
Joined: Sep 2015
Posts: 33
Likes: 1
I was having issues with the heat messing up my starter solenoid twice already in 2 months. So I replaced all battery cables with thicker guage wiring. I added thermal insulation ofer the cables that go to the starter and a wrapped the starter as well. Actually I did away with the alternator cable going to the starter. Chevy has not changed that stupid idea for many years. I had a 76 and 89 Chevy pickups and they put too many wires on a starter stud for my liking.
The cats were starting to degrade so I figured It was causing extra heat in the area by the starter. I figure I never ran them before so it shouldn't be a big deal. The only codes were po420 and po430 for the cats
However I read conflicting info on me needing a tune.
I only run 93 octane from shell, texaco or chevron gas from valero is horrible so I don't use that.
Im in San Antonio TX
The cats were starting to degrade so I figured It was causing extra heat in the area by the starter. I figure I never ran them before so it shouldn't be a big deal. The only codes were po420 and po430 for the cats
However I read conflicting info on me needing a tune.
I only run 93 octane from shell, texaco or chevron gas from valero is horrible so I don't use that.
Im in San Antonio TX
Safety Car
Joined: Nov 2006
Posts: 3,667
Likes: 159
I'm thinking you had other issues that was causing your exhaust to be too hot, and gutting the cats was not the solution to fix that problem.
There are a lot of things that can cause backfiring under acceleration, I would start out by trying to figure out why you were frying wires first, then go from there.
Have you looked at your spark plugs yet?
There are a lot of things that can cause backfiring under acceleration, I would start out by trying to figure out why you were frying wires first, then go from there.
Have you looked at your spark plugs yet?
Thread Starter
Intermediate
Joined: Sep 2015
Posts: 33
Likes: 1
I was was getting very high engine colant temps 230-245 after swapping the thermostat nothing changed so I gutted the cats. I think wires were getting cooked from exhaust/engine heat. Plus these cars have a undersized radiator. After that on highway I get 196-201 where before the car was always at 220 -230 babying it.
I figured it can't hurt gutting the cats since its emissions junk anyways. All my fords and other chevys never had a issue without them. However some say that's enough to mess up the computers tune. Plus lots of people run headders without cats so I figured no biggie. Maybe that's not the case with vettes.
Good point I haven't checked the plugs I'll try today. I changed plugs and wires 5k miles ago. The car has 70k miles now. Thanks
I figured it can't hurt gutting the cats since its emissions junk anyways. All my fords and other chevys never had a issue without them. However some say that's enough to mess up the computers tune. Plus lots of people run headders without cats so I figured no biggie. Maybe that's not the case with vettes.
Good point I haven't checked the plugs I'll try today. I changed plugs and wires 5k miles ago. The car has 70k miles now. Thanks
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Racer
Joined: Jun 2009
Posts: 374
Likes: 0
From: Houston Texas
No, that will do nothing for your issues. You need to have someone with tuning software turn off the rear o2s in the computer. This will trick the computer into thinking all is well and not throw any codes or act funny.
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,106
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
I recently had the same problem. Pull the plugs and check to see if the platinum tip is still there. The gap is supposed to be .040, but if the tip is missing, it'll be close to .080.
Thread Starter
Intermediate
Joined: Sep 2015
Posts: 33
Likes: 1
With these ls3 motors in a vette its easy to get to the plugs. Atleast with stock exhaust manifolds.
How about with headders? Is it a pain?
Also is there a limit on picture upload size? I tried and it said wrong format.
I'm using my phone to surf this forum.
Thanks
How about with headders? Is it a pain?
Also is there a limit on picture upload size? I tried and it said wrong format.
I'm using my phone to surf this forum.
Thanks
Safety Car
Joined: Nov 2006
Posts: 3,667
Likes: 159
It should be even easier to get to the plugs with headers, and inspect your plug wires, you may have a bad wire (overheated from the headers), if it is broken, you could be getting your backfire from a bad wire. Be careful removing and reinstalling the wires, same as any other vehicle.
Yes, there is a size limit on the file, but I also occasionally get that wrong format error too, don't know why. I can load the pic later and it loads fine.....
Something else still may be the issue with your engine overheating though...I run in close to 100 heat here in Florida, and have never seen over 210, even when sitting in heavy Orlando/Tampa traffic for long stop and go periods. I'm stock thermostat with my LS3 sounds like something is making it run lean to me. The plugs will tell if that is the case or not.
Yes, there is a size limit on the file, but I also occasionally get that wrong format error too, don't know why. I can load the pic later and it loads fine.....
Something else still may be the issue with your engine overheating though...I run in close to 100 heat here in Florida, and have never seen over 210, even when sitting in heavy Orlando/Tampa traffic for long stop and go periods. I'm stock thermostat with my LS3 sounds like something is making it run lean to me. The plugs will tell if that is the case or not.
Last edited by Seadawg; Sep 22, 2015 at 03:20 PM.
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,106
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
Thread Starter
Intermediate
Joined: Sep 2015
Posts: 33
Likes: 1
Most were 40 a couple were 45 and one was 50. Now all are exactly 40. <br/><br/>#6 had a little black soot on it.
Thread Starter
Intermediate
Joined: Sep 2015
Posts: 33
Likes: 1
Thsee were removed right after I turned the engine off after a 45 min drive home. I cleaned the MAF too. I did notice I was able to better seat a couple plug wires on the coil pack side. I pushed them in a little maybe a 1/8" or so.
I wasn't abe to fully check it out. Too many cops on my bacon detector lol. But on a quick down shift it pulled real strong and smooth. Tomorrow I'll romp it a little and see if it makes the gunshot style backfires.
I wasn't abe to fully check it out. Too many cops on my bacon detector lol. But on a quick down shift it pulled real strong and smooth. Tomorrow I'll romp it a little and see if it makes the gunshot style backfires.