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Discussion Starter · #1 ·
my car after being turbo'd for 70,000 miles suddenly started to backfire. I had a leaky valve cover and thought that my coilpacks were leaking. My car is running hella rich, 4 foot flames shoot out of my tail pipe when i backfire. It back fires a 4200 rpm and 5300 rmp. If i smash on the gas to 10 psi or higher it runs through it without backfiring. I did a search and could find nothing that would help. Will check for vacuum leaks.

Derek

As some of you thought. Air temp. See cold weather post above.

Thanks for your help.
 

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Discussion Starter · #2 ·
i may have found the problem, They T'd my vacuum lines with my BOV, when i'm driving in vacuum does it not leak abit? if so this would create a vacuum leak in my system would it not? This is a F/I car to answer the 3 pm's


Derek
 

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maxxpsi said:
i may have found the problem, They T'd my vacuum lines with my BOV, when i'm driving in vacuum does it not leak abit? if so this would create a vacuum leak in my system would it not? This is a F/I car to answer the 3 pm's


Derek
Derek, are you running a MAP sensor setup? If so, make sure the vacuum line to it in good shape and is not shared with anything such as a boost gauge or BOV. try to run a separate line for each thing in your vacuum line setup, i.e Bov, Wastegate, Boost gauge, MAP if you have one, etc..

Not sure if this would cause a backfire issue, but if you've changed anything recently, could be a possibility. Check to see if any lines have any cracks in them, etc...

What is your vacuum at idle? is it stable, or does it oscillate?

Basically, has ANYTHING changed since you've had the backfire issues?


Kane
 

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Another thought, look through you exhaust system, make sure it's all nice and tight, no leaks. Same with you intake tract. A leaky gasket allowing extra air in during a vacuum pull can ignite in the system somewhere, causing a backfire.

Kane
 

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Discussion Starter · #5 ·
fixed the vacuum line-still does it. My car is running really rich for some reason. Could it be that it is so cold. Does the motor compinsate for dense air and add fuel? I started when we go really cold. The air entering my motor today was 21 degreed post intercooler-highway speed. You can feel it bog down after 4200 rpm and up. I am solid blue on my arm1. you can see the fuel dump out the tail pipe.
 

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I take it you've reset the ecu by dissconnecting the battery? If not, try that.

With such cold air coming in, it might just be maxing out the injector pulse width trying to compensate for the high oxygen content and just saturating the mixture when going full duty cycle.

What are you running for an EMS besides the AIC? emanage or something?


Kane

maxxpsi said:
fixed the vacuum line-still does it. My car is running really rich for some reason. Could it be that it is so cold. Does the motor compinsate for dense air and add fuel? I started when we go really cold. The air entering my motor today was 21 degreed post intercooler-highway speed. You can feel it bog down after 4200 rpm and up. I am solid blue on my arm1. you can see the fuel dump out the tail pipe.
 

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Discussion Starter · #7 ·
i reset it. The car ran awesome in the shop when we dyno'd it. On the way home it started running weird. I can play with my stock fuel maps-add fuel,remove fuel,advance timing and retard it. with the FTC1. I am just nervous about touching the fuel maps again.

Derek
 

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Discussion Starter · #8 ·
oh ya, the coolant running through my intake manifold has been disconnected. So it is not heated.
 

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Discussion Starter · #10 ·
is300sam2002 said:
Intermittent ignition loss would cause backfiring due to excess fuel/air buildup, but you would notice if it was misfiring.
i can see it in my tach, what would cause this after being turbo'd for so long. We are extremely cold here. could that do it?


Derek
 

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maxxpsi said:
is300sam2002 said:
Intermittent ignition loss would cause backfiring due to excess fuel/air buildup, but you would notice if it was misfiring.
i can see it in my tach, what would cause this after being turbo'd for so long. We are extremely cold here. could that do it?


Derek
From what I've read, with a turbo setup and the controllers that go with it, you need to retune for extreme temperature changes. I think you're on the right track re the air temperature.

If it's ignition, wires can break down or coils, etc can get weak and fail under extreme conditions.

The reason I thought of the ignition fault is that with old cars we used to turn off the ignition for a few seconds while coasting, and then turn it back on and get some really awesome backfires. Just for kicks.
 
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