Still breaking up and backfiring
07-29-2010, 10:27 PM
#1
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Still breaking up and backfiring I've nearly reached the end of the road with what to do to solve this. I've brought up this problem at different stages trying to solve it and since it's progressed quite a bit further I'll try again to get someone who might have an idea of what's wrong with.
The problem is every time you get in it WOT and the rpms get around 6K sometimes less it just breaks up backfires sputters and proceeds to like clockwork shoot a flame out the exhaust. Here's the kicker so far we can't reproduce on the dyno only on pavement.
LS1 418CI Camaro
F1A Procharger @17 PSI
TH400 with 730RWHP
96LB Delphi LI Injectors
TR8 Plugs tried all gaps from .018-.030
Tuned for 93 octane have run 112 octane to try and rule out pre-ign
Timing around 16* depending on circumstances have brought it all the way back to 10* again to rule out detonation.
Lonnies twin pumper kit -8 feed with boost reference regulator fuel pressure is good and boost reference is working correctly.
3 Bar MAP
Open loop SD tune
The whole entire wiring harness has been removed checked inside and out and no problems. The PCM has been swapped out as well. Changed the battery and alternator added grounds checked grounds swapped out the + wire to the starter alternator and battery. Starter has been replaced. Crank position sensor has been replaced. TPS has been replaced. Valve springs are patriot dual springs.
The only thing I can say is that when it's relatively cold not heat soaked it doesn't do it. The hotter it gets the easier it seems to do it. One observation and the reason I changed the alternator is the when cold the voltmeter says 14-14.5 once it heats up the voltage 12.5-13 the new alternator does the same thing.
It really seems electrical in nature since it's not just one cylinder dropping off its all of them like there's a major short or it runs out of juice.
The trigger for this was when I re flashed my TQ to a lower stall it was way loose before. This obviously loads the engine more. The tune worked before now it doesn't I did have it retuned on the dyno but only very minor tweaks were needed and it ran perfect. Once on the track it started this.
I know it's a lot of stuff but the pro's around here are giving up and just want to tear everything down to try and find it (which we may do) but any ideas would be greatly appreciated.
The problem is every time you get in it WOT and the rpms get around 6K sometimes less it just breaks up backfires sputters and proceeds to like clockwork shoot a flame out the exhaust. Here's the kicker so far we can't reproduce on the dyno only on pavement.
LS1 418CI Camaro
F1A Procharger @17 PSI
TH400 with 730RWHP
96LB Delphi LI Injectors
TR8 Plugs tried all gaps from .018-.030
Tuned for 93 octane have run 112 octane to try and rule out pre-ign
Timing around 16* depending on circumstances have brought it all the way back to 10* again to rule out detonation.
Lonnies twin pumper kit -8 feed with boost reference regulator fuel pressure is good and boost reference is working correctly.
3 Bar MAP
Open loop SD tune
The whole entire wiring harness has been removed checked inside and out and no problems. The PCM has been swapped out as well. Changed the battery and alternator added grounds checked grounds swapped out the + wire to the starter alternator and battery. Starter has been replaced. Crank position sensor has been replaced. TPS has been replaced. Valve springs are patriot dual springs.
The only thing I can say is that when it's relatively cold not heat soaked it doesn't do it. The hotter it gets the easier it seems to do it. One observation and the reason I changed the alternator is the when cold the voltmeter says 14-14.5 once it heats up the voltage 12.5-13 the new alternator does the same thing.
It really seems electrical in nature since it's not just one cylinder dropping off its all of them like there's a major short or it runs out of juice.
The trigger for this was when I re flashed my TQ to a lower stall it was way loose before. This obviously loads the engine more. The tune worked before now it doesn't I did have it retuned on the dyno but only very minor tweaks were needed and it ran perfect. Once on the track it started this.
I know it's a lot of stuff but the pro's around here are giving up and just want to tear everything down to try and find it (which we may do) but any ideas would be greatly appreciated.
Last edited by laughatrice; 08-08-2010 at 02:24 PM.
07-29-2010, 10:46 PM
#2
i presume you are scanning the car every time you have this problem dyno/street, where is the rev limiter set? I presume you are manual valve body tranny?
It sounds like you are on the limiter, when you are on the street does it kill the tires, if so your tack in the car may not be sweeping as fast as the engine accelerating
just a thought try back to back pulls, try bumping the limter up 300rpms and see
It sounds like you are on the limiter, when you are on the street does it kill the tires, if so your tack in the car may not be sweeping as fast as the engine accelerating
just a thought try back to back pulls, try bumping the limter up 300rpms and see
07-29-2010, 11:08 PM
#3
Launching!
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i presume you are scanning the car every time you have this problem dyno/street, where is the rev limiter set? I presume you are manual valve body tranny?
It sounds like you are on the limiter, when you are on the street does it kill the tires, if so your tack in the car may not be sweeping as fast as the engine accelerating
just a thought try back to back pulls, try bumping the limter up 300rpms and see
It sounds like you are on the limiter, when you are on the street does it kill the tires, if so your tack in the car may not be sweeping as fast as the engine accelerating
just a thought try back to back pulls, try bumping the limter up 300rpms and see
Another thing is often times while its on the street and the tires are spinning you can hear it bounce off the limiter normally without any violence. It only has a tendency to backfire when it's loaded like when the tires hook good. Maybe when it's loaded and catches the limiter good it sputters and backfires but again the scan shows it only getting to 6K
Here's the link to my other thread with the scan file and the tune FWIW. The timing tables have been drastically reduced to see if it help it didn't.
https://ls1tech.com/forums/pcm-diagn...nce-table.html
07-29-2010, 11:11 PM
#4
What's the AFR doing leading up to the problem? Does it only happen in high gear? What compression are you running?
16*, 17#, and 93 oct seems like your pushing a little hard there unless this thing has real low compression not that that is causing this problem but just sayin'.
16*, 17#, and 93 oct seems like your pushing a little hard there unless this thing has real low compression not that that is causing this problem but just sayin'.
07-29-2010, 11:50 PM
#5
Just looked at the other thread, Have you checked plugs again lately, it def. sounds like it is going lean, If the same plugs are melted, you may have some injectors getting weak on the car, if you have a couple weak injectors the ones that are working correctly are just dumping extra fuel in those cylinders making the afr in the ball park
pull the plugs and read if the fuel rings are way off
pull the plugs and read if the fuel rings are way off
07-30-2010, 06:28 AM
#6
I agree, I'd swap out the injectors and see if they take care of the problem. Bob
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PM's disabled, please e-mail me
E-mail: brutespeed@gmail.comob@brutespeed.com
https://brutespeed.com/ Link to website
07-30-2010, 02:18 PM
#7
Launching!
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On the injector subject I did have one random injector go bad over the winter for no reason I put zero street miles on this car it's all track. One cylinder wasn't firing at all I mean the plug was pristine didn't hit once I swapped out the injector and it was fine. Funny thing was the injector still worked if you activated it off the car and blew some carb cleaner through it but on the fuel rail nothing.
Maybe the other ones are going bad as well.
Maybe the other ones are going bad as well.
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07-30-2010, 04:22 PM
#8
If plugs look ok replace wires. I had some burnt wires ,problem of course worse with turbo cars burning them from the heat but still burnt /bad wire can do this.I even had a dud new gmpp wire lately.Accidentally touched the wire and it zapped me good.Replaced it of course.
If its not gap and you have tried that then usually its wires and sometimes coils. Can you borrow some coils to try. Also its harder to find problems when running speed density since it usually means you can't check misfires. On my hptuners I can put maf back in for temp and turn maf back on and watch individual cylinder misfires. If you have misfires you will also usually see o2s being weird on that bank if you run sd closed loop for a bit.
And fuel well guess it could be an individual injector maybe but key is where is it backfiring, in exhaust or intake. In exhaust pretty much unburnt fuel and that usually is
igntion. You could have a damaged plug wire or one not making good solid contact or one not even plugged in fully.I would bet on a wire issue. Mine was exactly similar.You could go part throttle fine but hit boost and go wot instant machine gun noises.
Found the bad wires and ran like butter after that.
If its not gap and you have tried that then usually its wires and sometimes coils. Can you borrow some coils to try. Also its harder to find problems when running speed density since it usually means you can't check misfires. On my hptuners I can put maf back in for temp and turn maf back on and watch individual cylinder misfires. If you have misfires you will also usually see o2s being weird on that bank if you run sd closed loop for a bit.
And fuel well guess it could be an individual injector maybe but key is where is it backfiring, in exhaust or intake. In exhaust pretty much unburnt fuel and that usually is
igntion. You could have a damaged plug wire or one not making good solid contact or one not even plugged in fully.I would bet on a wire issue. Mine was exactly similar.You could go part throttle fine but hit boost and go wot instant machine gun noises.
Found the bad wires and ran like butter after that.
07-30-2010, 04:38 PM
#9
Launching!
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If plugs look ok replace wires. I had some burnt wires ,problem of course worse with turbo cars burning them from the heat but still burnt /bad wire can do this.I even had a dud new gmpp wire lately.Accidentally touched the wire and it zapped me good.Replaced it of course.
If its not gap and you have tried that then usually its wires and sometimes coils. Can you borrow some coils to try. Also its harder to find problems when running speed density since it usually means you can't check misfires. On my hptuners I can put maf back in for temp and turn maf back on and watch individual cylinder misfires. If you have misfires you will also usually see o2s being weird on that bank if you run sd closed loop for a bit.
And fuel well guess it could be an individual injector maybe but key is where is it backfiring, in exhaust or intake. In exhaust pretty much unburnt fuel and that usually is
igntion. You could have a damaged plug wire or one not making good solid contact or one not even plugged in fully.I would bet on a wire issue. Mine was exactly similar.You could go part throttle fine but hit boost and go wot instant machine gun noises.
Found the bad wires and ran like butter after that.
If its not gap and you have tried that then usually its wires and sometimes coils. Can you borrow some coils to try. Also its harder to find problems when running speed density since it usually means you can't check misfires. On my hptuners I can put maf back in for temp and turn maf back on and watch individual cylinder misfires. If you have misfires you will also usually see o2s being weird on that bank if you run sd closed loop for a bit.
And fuel well guess it could be an individual injector maybe but key is where is it backfiring, in exhaust or intake. In exhaust pretty much unburnt fuel and that usually is
igntion. You could have a damaged plug wire or one not making good solid contact or one not even plugged in fully.I would bet on a wire issue. Mine was exactly similar.You could go part throttle fine but hit boost and go wot instant machine gun noises.
Found the bad wires and ran like butter after that.
I'm with you though it seems like an ignition issue but so far that has tuned up nothing and I've checked all I know. Here's why I'm leaning away from coil packs. What are the odds that all of the or most of them would go bad at once. One coil pack would certainly cause a drop in power and some popping but it wouldn't cause the car to die I don't think. This isn't just one cylinder dropping off this is the whole engine popping like hell followed by an instant shutdown and then a backfire a second or so later after the engine cutoff it sounds horrible like a gunshot. It's like the key was turned off and then turned back on. That leads me to a loose wire under the dash or bad PCM but we swapped that out and something along those lines would cause intermittent issues all the time not just at peak HP/TQ.
I don't know much though so maybe one coil pack could cause this but I was thinking something more broad since the car completely dies.
Unfortunately I don't have the option to go back to MAF or open loop the wiring harness has been made to delete all that stuff.
Thanks for the help
07-30-2010, 08:28 PM
#10
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I've nearly reached the end of the road with what to do to solve this. I've brought up this problem at different stages trying to solve it and since it's progressed quite a bit further I'll try again to get someone who might have an idea of what's wrong with.
The problem is every time you get in it WOT and the rpms get around 6K sometimes less it just breaks up backfires sputters and proceeds to like clockwork shoot a flame out the exhaust. Here's the kicker so far we can't reproduce on the dyno only on pavement.
LS1 418CI Camaro
F1A Procharger @17 PSI
TH400 with 730RWHP
96LB Delphi LI Injectors
TR8 Plugs tried all gaps from .018-.030
Tuned for 93 octane have run 112 octane to try and rule out pre-ign
Timing around 16* depending on circumstances have brought it all the way back to 10* again to rule out detonation.
Lonnies twin pumper kit -8 feed with boost reference regulator fuel pressure is good and boost reference is working correctly.
3 Bar MAP
Open loop SD tune
The whole entire wiring harness has been removed checked inside and out and no problems. The PCM has been swapped out as well. Changed the battery and alternator added grounds checked grounds swapped out the + wire to the starter alternator and battery. Starter has been replaced. Crank position sensor has been replaced. TPS has been replaced. Valve springs are patriot dual springs.
The only thing I can say is that when it's relatively cold not heat soaked it doesn't do it. The hotter it gets the easier it seems to do it. One observation and the reason I changed the alternator is the when cold the voltmeter says 14-14.5 once it heats up the voltage 12.5-13 the new alternator does the same thing.
It really seems electrical in nature since it's not just one cylinder dropping off its all of them like there's a major short or it runs out of juice. The tuner is convinced there's no way it's the tune but I have damn near replaced everything but the tune.
The trigger for this was when I re flashed my TQ to a lower stall it was way loose before. This obviously loads the engine more. The tune worked before now it doesn't I did have it retuned on the dyno but only very minor tweaks were needed and it ran perfect. Once on the track it started this.
I know it's a lot of stuff but the pro's around here are giving up and just want to tear everything down to try and find it (which we may do) but any ideas would be greatly appreciated.
The problem is every time you get in it WOT and the rpms get around 6K sometimes less it just breaks up backfires sputters and proceeds to like clockwork shoot a flame out the exhaust. Here's the kicker so far we can't reproduce on the dyno only on pavement.
LS1 418CI Camaro
F1A Procharger @17 PSI
TH400 with 730RWHP
96LB Delphi LI Injectors
TR8 Plugs tried all gaps from .018-.030
Tuned for 93 octane have run 112 octane to try and rule out pre-ign
Timing around 16* depending on circumstances have brought it all the way back to 10* again to rule out detonation.
Lonnies twin pumper kit -8 feed with boost reference regulator fuel pressure is good and boost reference is working correctly.
3 Bar MAP
Open loop SD tune
The whole entire wiring harness has been removed checked inside and out and no problems. The PCM has been swapped out as well. Changed the battery and alternator added grounds checked grounds swapped out the + wire to the starter alternator and battery. Starter has been replaced. Crank position sensor has been replaced. TPS has been replaced. Valve springs are patriot dual springs.
The only thing I can say is that when it's relatively cold not heat soaked it doesn't do it. The hotter it gets the easier it seems to do it. One observation and the reason I changed the alternator is the when cold the voltmeter says 14-14.5 once it heats up the voltage 12.5-13 the new alternator does the same thing.
It really seems electrical in nature since it's not just one cylinder dropping off its all of them like there's a major short or it runs out of juice. The tuner is convinced there's no way it's the tune but I have damn near replaced everything but the tune.
The trigger for this was when I re flashed my TQ to a lower stall it was way loose before. This obviously loads the engine more. The tune worked before now it doesn't I did have it retuned on the dyno but only very minor tweaks were needed and it ran perfect. Once on the track it started this.
I know it's a lot of stuff but the pro's around here are giving up and just want to tear everything down to try and find it (which we may do) but any ideas would be greatly appreciated.
07-30-2010, 09:07 PM
#12
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Yeah you were lined beside Nick in my car and Nick didnt go for some reason so I could hear yours good and it didnt sound like it could be a plug or plug wire or an injector because the whole engine stopped and then backfired not just a miss it quit firing completely but whats weird is that it wont do it on the dyno so that means that it has something to do with the launch like something moving backwards and shorting out a wire or something. Ive seen this happen before when a battery slides back and shorts out. j
07-31-2010, 04:16 PM
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Yea I remember you car what you heard was pretty much in line with what it does everytime. We thought it was the battery as well unfortunately we ruled it out. Yea you would think it's a loose wire or something somewhere since it's fine on the dyno however no luck finding that so far. The thing about it being something loose why doesn't it do it when the car hits a bump or brakes hard it only does it at peak power not even when it's under the most g's right at the launch it almost always waits until the top of the power band.
07-31-2010, 04:39 PM
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Yea quite a bit I removed my two step and soldered all the connections back didn't fix it still have my water pump, line lock, t-brake, and shift light. I'm considering removing all my accessories of the + post and pulling fuse out for stock stuff and seeing if it fix's it. With any luck it would and I could add them back until I isolate the problem.
07-31-2010, 05:15 PM
#17
Just trash canned a set of those injs for the very same reason. [V-sicks Buick turbo, in the mid nines.]
The customer complained about a particular cyl being fubar. I flow tested them, and found them all over the map..Didn't finish the cleaning.. In the trashcan...
A flow test would be a good idea.. Maybe you won't be so likely to drive over the crank!
The customer complained about a particular cyl being fubar. I flow tested them, and found them all over the map..Didn't finish the cleaning.. In the trashcan...
A flow test would be a good idea.. Maybe you won't be so likely to drive over the crank!
07-31-2010, 06:56 PM
#18
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Fuel slosh was one of the first thing I assumed since I had a crappy DIY fuel bucket with two pumps jammed in there. Anyway I put lonnies kit in no change and I'm not using the HOBBS switch as not to complicate this problem further.
Interesting would you say the car did the same thing where it lost all power at high rpms and then proceeded to sputter die and backfire. If so I'll replace the injectors ASAP of course I'll have to probably retune it.
Yea no kidding about the crank I can't imagine the stress this is putting on my engine trying to diagnose this.
Just trash canned a set of those injs for the very same reason. [V-sicks Buick turbo, in the mid nines.]
The customer complained about a particular cyl being fubar. I flow tested them, and found them all over the map..Didn't finish the cleaning.. In the trashcan...
A flow test would be a good idea.. Maybe you won't be so likely to drive over the crank!
The customer complained about a particular cyl being fubar. I flow tested them, and found them all over the map..Didn't finish the cleaning.. In the trashcan...
A flow test would be a good idea.. Maybe you won't be so likely to drive over the crank!
Yea no kidding about the crank I can't imagine the stress this is putting on my engine trying to diagnose this.
07-31-2010, 07:26 PM
#19
Yea quite a bit I removed my two step and soldered all the connections back didn't fix it still have my water pump, line lock, t-brake, and shift light. I'm considering removing all my accessories of the + post and pulling fuse out for stock stuff and seeing if it fix's it. With any luck it would and I could add them back until I isolate the problem.
07-31-2010, 07:29 PM
#20
Also, not sure if it has been mentioned but a slightly damaged reluctor could become a problem at higher RPM's. Maybe when the oil pushes back to the back of the pan, it's having problems picking up the damaged tooth? I'm just reaching here as it seems that you have addressed all the obvious stuff.