backfiring =/
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12-27-2009, 10:05 AM
#9
It could be a fuel issue since it's only on the big end under WOT. In the meantime, I'd also check your fuel filter and make sure the plugs have the same gap you were running before to rule out it blowing out the spark.
Do you have a fuel pressure and wideband A/F gauge in the car? Does it still do it if you turn the boost down a bit?
Do you have a fuel pressure and wideband A/F gauge in the car? Does it still do it if you turn the boost down a bit?
12-27-2009, 10:46 AM
#12
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My first guess woulld be a gas issue.
Unless you are using a different tank. It will take a tank or two to get all the resedue of bad gas out.
I'd put some octane booster, or stp gum out in it. That way the injectors or carb jets get cleaned.
Are you carb or injected?
Unless you are using a different tank. It will take a tank or two to get all the resedue of bad gas out.
I'd put some octane booster, or stp gum out in it. That way the injectors or carb jets get cleaned.
Are you carb or injected?
12-27-2009, 10:53 AM
#13
I had machine gun noises on my tt a few times. It was burnt wires every time.Finally went to stock wires with stock ls1 heat shields and that works best,fancy granatelli wires cooked bad in my car. Never figured it was wires but it was.
Plug gap for sure can let spark blow out under boost. I run .028 with current autolite 103s.
You can turn up dwell if you have tuning program like hptuners or upgrade to truck coils.
Check fuel supply, filter,pump and hopefully you are not running out of injector.
It should be one of the above things and valve springs might be gone too.
Plug gap for sure can let spark blow out under boost. I run .028 with current autolite 103s.
You can turn up dwell if you have tuning program like hptuners or upgrade to truck coils.
Check fuel supply, filter,pump and hopefully you are not running out of injector.
It should be one of the above things and valve springs might be gone too.
12-28-2009, 07:44 PM
#14
Launching!
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thanks for all the tips ill do that over the weekend and let you guys know whats up ....the sparkplug wires arent touching anything hot and they go arround the headers so ill look at that too ,ill look inside the valve covers too but the springs were new ,maybe a bad valve ?
01-13-2010, 01:12 AM
#16
You definitely need some sort of scan tool so you can monitor your data or you are flying blind. I wouldn't go WOT again without some data - creep up on WOT in small stages, confirming that your AFR and Knock Retard #'s are solid before you continue. Consider investing in some race gas for insurance against detonation while you troubleshoot. $50 in gas is nothing if it saves you a piston or valve, eh? I wanna see that thing running good again next time we meet 
Jim
Jim
01-13-2010, 08:57 AM
#17
Had the problem repeatedly. It was wires every time. Even cooked some very expensive granatelli wires. Finally went back to stock gmpp wires with the stock heat shields and so far seem to be fine. I didn't ceramic coat my exhaust manifolds and turbo exhaust housings but do plan on doing this sooner or later. I have heat shields on my exhaust manifolds from aps though. Course a lot depends on your particular setup.
As said other things that cause similar problems are spark plug gap.I run around .028 to .030 currently. Might go down to .025 at higher boost. Also iridium plugs last longer and you can run a colder heat range than the normal copper plugs people like to run.
I am currently running autolite think 103 but going to ngktr8ix this coming season.Plan on upping boost to around the 15 range for daily driving and 20 maybe occasional max.
At least plugs are pretty easy to change out on my setup.Seen some that are real nightmares.
Fuel is of course another thing that can affect things. Checking fuel pressure,making sure you have adequate fuel and the injectors are not at the end of their capability are good ideas, unrestricted fuel filter is a good thing.
But 99/100 when the car brakes up under wot and I called it a machine gun sound it is wires or plugs.
And it is a good idea to check valve springs every couple years and maybe even more often if you are running high lift and the springs are close. Turbos are hard on valve springs.
As said other things that cause similar problems are spark plug gap.I run around .028 to .030 currently. Might go down to .025 at higher boost. Also iridium plugs last longer and you can run a colder heat range than the normal copper plugs people like to run.
I am currently running autolite think 103 but going to ngktr8ix this coming season.Plan on upping boost to around the 15 range for daily driving and 20 maybe occasional max.
At least plugs are pretty easy to change out on my setup.Seen some that are real nightmares.
Fuel is of course another thing that can affect things. Checking fuel pressure,making sure you have adequate fuel and the injectors are not at the end of their capability are good ideas, unrestricted fuel filter is a good thing.
But 99/100 when the car brakes up under wot and I called it a machine gun sound it is wires or plugs.
And it is a good idea to check valve springs every couple years and maybe even more often if you are running high lift and the springs are close. Turbos are hard on valve springs.
01-13-2010, 09:58 AM
#18
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well thanks for all the info ,I will replace the wires for sure but im kinda wondering where to get them ,last time i pieced some msd wires together ,is there any out there for custom lenght ? i run them arround the headers not straight down from the coil ,and the only diagnose equipment i have is a snap-on solus ,I dont have any hp tuners or efilive
Jim we will meet again soon !
Jim we will meet again soon !
