Backfire/missing out

[calvinespree]

It's been awhile since I posted (someone decided to hit my car) now that the body work is out of the way I almost have the car running perfect but I ran into a problem with it missing out, or backfiring. Sometimes it sounds like a miss and sometimes it sounds like a pop. Really anywhere between 4k - 5k rpm. Any ideas what it could be? Timing too low?
2010 Camaro ss. 278/297 .625 cam. Pulley. Headers. Cai. Tb spacer. Straight pipe up to glass packs.
I'm on mobile right now but I can post the tune of anyone can help me.

[calvinespree]

Anybody?

[GHuggins]

I've seen this on Fords being caused by spark plugs. Plugs glow red and while incoming fuel hits them, they pop back out the intake.

Could also be a valve sticking or if you've got dual valve springs a broken outer spring not allowing valve to fully seat, but this usually shows up on idle. Guess it could show up at high revs due to valve floatage?

[calvinespree]

I've seen this on Fords being caused by spark plugs. Plugs glow red and while incoming fuel hits them, they pop back out the intake.

Could also be a valve sticking or if you've got dual valve springs a broken outer spring not allowing valve to fully seat, but this usually shows up on idle. Guess it could show up at high revs due to valve floatage?

Thanks, I will check springs in the morning and play with the tune a little more

[calvinespree]

This is a log i made with a MAF config, fuel trims, kr, etc as well as my current tune. The problem seems to be above 4k rpm it was hesitating and popping not wanting to go. Now it seems as it wants to go but its still popping sputtering when i push it the the top end.
Checked fuel pressure its fine. 57-58psi
No broken valve springs.
Brand new plugs installed today before the log.
Wires are 3 months old.
I had the car running nearly perfect with no backfiring or popping, i sent it to the body shop to repair the damages from an accident and the car has been doing this since the day i picked it up from them.
I've heard that it could be my glasspacks have came apart and are causing a restriction? any opinions on this? Its the first time ive heard of something like that. Thanks to anyone who can help!

[GHuggins]

This is a log i made with a MAF config, fuel trims, kr, etc as well as my current tune. The problem seems to be above 4k rpm it was hesitating and popping not wanting to go. Now it seems as it wants to go but its still popping sputtering when i push it the the top end.
Checked fuel pressure its fine. 57-58psi
No broken valve springs.
Brand new plugs installed today before the log.
Wires are 3 months old.
I had the car running nearly perfect with no backfiring or popping, i sent it to the body shop to repair the damages from an accident and the car has been doing this since the day i picked it up from them.
I've heard that it could be my glasspacks have came apart and are causing a restriction? any opinions on this? Its the first time ive heard of something like that. Thanks to anyone who can help!

The absolute only other thing I can think of since "the bodyshop" is when this started, is to check all of you grounds and make sure there both tight and not tightened down onto paint. Have also seen grounds cause some serious problems. I guess that all depends on where the body work was done or what part of the vehicle was repaired. Would also be interrested in how they drove it or if they noticed a problem.

The only thing I saw in your datalog was some serious timing being pulled and the fact that fueling wasn't just right. You running negative fuel trims at cold idle then up to +10's hot when the problem was occuring. In fact all I could really see in the datalog was a "hinted" misfire, I didn't even see the map spiking like it was popping back out the intake. Hopefully someone on here can help.

How long was it at the body shop? Weather suddenly change?

[calvinespree]

The absolute only other thing I can think of since "the bodyshop" is when this started, is to check all of you grounds and make sure there both tight and not tightened down onto paint. Have also seen grounds cause some serious problems. I guess that all depends on where the body work was done or what part of the vehicle was repaired. Would also be interrested in how they drove it or if they noticed a problem.

The only thing I saw in your datalog was some serious timing being pulled and the fact that fueling wasn't just right. You running negative fuel trims at cold idle then up to +10's hot when the problem was occuring. In fact all I could really see in the datalog was a "hinted" misfire, I didn't even see the map spiking like it was popping back out the intake. Hopefully someone on here can help.

How long was it at the body shop? Weather suddenly change?

They repaired the entire driver side of the the car, it stayed in the body shop almost a month. Weather is pretty close to the same weather that I tuned it in, not sure what else to go at but I will retune in the am. The backfire is definitely coming through the exhaust. Sounds like I'm firing cannons out the truck with my exhaust set up

[GHuggins]

They repaired the entire driver side of the the car, it stayed in the body shop almost a month. Weather is pretty close to the same weather that I tuned it in, not sure what else to go at but I will retune in the am. The backfire is definitely coming through the exhaust. Sounds like I'm firing cannons out the truck with my exhaust set up

If it's in the exhaust it's misfiring... Try replacing the plug wires since you haven't replaced them yet. Thought it looked like a "hinted miss" in the datalog with the maf and map dropping out a little. Since it just started after body work, don't worry about the tune just yet.

[calvinespree]

If it's in the exhaust it's misfiring... Try replacing the plug wires since you haven't replaced them yet. Thought it looked like a "hinted miss" in the datalog with the maf and map dropping out a little. Since it just started after body work, don't worry about the tune just yet.

Current plug wires are only about 3 months old? Think they could be bad already?

[GHuggins]

Current plug wires are only about 3 months old? Think they could be bad already?

Tell ya what. Find a cheap set and put them on, just for a check. If you have headers, the heat really does a number on them. Reason why we only recommend installing headers with plug wires with socks... Put headers on a guys ls6 last month. He didn't want wires. Had msd's. Needless to say they lasted 1.5 weeks with the headers.

It's definately missing. Just need to cover the basics.

[GHuggins]

Just wanted to check and see if you figured anything out yet or not? Just dawned on me that you could possibly use a scanner and check your misfire history, but I can't for the life of me remember if gm even watches misfires above 3000 rpms or not. I know above a certain rpm it's almost impossible for the ecm to detect the miss, so it won't look for it or atleast as far as I know that's how they are.

[calvinespree]

Just wanted to check and see if you figured anything out yet or not? Just dawned on me that you could possibly use a scanner and check your misfire history, but I can't for the life of me remember if gm even watches misfires above 3000 rpms or not. I know above a certain rpm it's almost impossible for the ecm to detect the miss, so it won't look for it or atleast as far as I know that's how they are.

I found out something caused my maf to lose calibrion and make me run extremely lean. I hooked the wideband up to it and I was nearly 3 afr points away from what I was commanding in most places. So I've been driving around today logging afr error and correcting my maf curve and it has cured the problem. I would still like to know what happened with my maf it confuses me completely on how it ran so good with the calibration before and for it to be all the way off track now.

[GHuggins]

Guess it could have been some sort of unusual "logic lock" if they had the battery disconnected for a long period of time, but I agree, you should have had more off in the tune than just the MAF cals if this were the case.

I was assuming that the tune had been unchanged and is why I was focussing more on actual misfire causes in my previous post.

Are you sure your MAF doesn't have some trash on the sensor "heat" wires? I would take it out and clean it before adjusting the tune if you compare your previous tune to your new one and they're way off. I could definately see "trash" or body filler dust getting on them for some reason or another being more likely over just completely losing the MAF cal and only the MAF cal.