need help car is backfiring
Thread Starter
Pro
Joined: Feb 2003
Posts: 540
Likes: 1
From: Taunton MA
need help car is backfiring
i need help when i took the car out of storage this year the car was backfiring slightly. I thought that the backfire was due to having bad gas or the opti was going bad. so i put 5 gal of fresh gas in the tank with a fuel stablizer. still was backfiring. I then instslled an msd opti and it ran about the same for a little while and progressivley got worst. so i then pulled the spark plugs and all of bank 2 was carbon fouled and bank 1 was gas fouled. any ideas of what it might be?
Race Director
Joined: Sep 2005
Posts: 10,878
Likes: 1
St. Jude Donor '07
Lots of possibilities.
Running rich?
Leaking injectors?
Timing way off?
Wrong temperature plugs?
Lots of short drives?
Plug wiress in wrong order?
FYI:
Fuel stabilizer is worthless in a summer vehicle. So is iso-alcohol in all vehicles. Winter stored vehicles' fuel stays cool enough to not lose the additives to aid in evaporation. Summer stored vehicles' tanks can get warm enough to allow these to evaporate and cause varnish. All fuel in the US is 10% alcohol minimum. Anything more than 10% will not absorb any more water or un freeze a line.
Running rich?
Leaking injectors?
Timing way off?
Wrong temperature plugs?
Lots of short drives?
Plug wiress in wrong order?
FYI:
Fuel stabilizer is worthless in a summer vehicle. So is iso-alcohol in all vehicles. Winter stored vehicles' fuel stays cool enough to not lose the additives to aid in evaporation. Summer stored vehicles' tanks can get warm enough to allow these to evaporate and cause varnish. All fuel in the US is 10% alcohol minimum. Anything more than 10% will not absorb any more water or un freeze a line.
Thread Starter
Pro
Joined: Feb 2003
Posts: 540
Likes: 1
From: Taunton MA
Lots of possibilities.
Running rich?
Leaking injectors?
Timing way off?
Wrong temperature plugs?
Lots of short drives?
Plug wiress in wrong order?
FYI:
Fuel stabilizer is worthless in a summer vehicle. So is iso-alcohol in all vehicles. Winter stored vehicles' fuel stays cool enough to not lose the additives to aid in evaporation. Summer stored vehicles' tanks can get warm enough to allow these to evaporate and cause varnish. All fuel in the US is 10% alcohol minimum. Anything more than 10% will not absorb any more water or un freeze a line.
Running rich?
Leaking injectors?
Timing way off?
Wrong temperature plugs?
Lots of short drives?
Plug wiress in wrong order?
FYI:
Fuel stabilizer is worthless in a summer vehicle. So is iso-alcohol in all vehicles. Winter stored vehicles' fuel stays cool enough to not lose the additives to aid in evaporation. Summer stored vehicles' tanks can get warm enough to allow these to evaporate and cause varnish. All fuel in the US is 10% alcohol minimum. Anything more than 10% will not absorb any more water or un freeze a line.
any other input on this would be great because i dont want to start throwing parts at the car.
Safety Car
Joined: Jan 2006
Posts: 3,566
Likes: 4
From: Mt Laurel NJ
St. Jude Donor '06-'07
I Hate to be the one to ask, but do you have a FSM? You should be able to figure it out w/ one. I will say that it sounds like a injector problem. Try ohming each injector, I think LT1 injectors should be about 14 to 15 ohms.
I would try that first, just to make sure they are OK.
Randy
I would try that first, just to make sure they are OK.
Randy
Race Director
Joined: Sep 2005
Posts: 10,878
Likes: 1
St. Jude Donor '07
Are you getting any codes?
I'm not an LT1 expert, but I would imagine that any sensor issues that would cause performance issues would throw a code or two.
Generally, carbon fouled plugs indicate a weak ignition system or computer driven control issues. That it is bank-biased tells me that it could be the sensors.
I'm not an LT1 expert, but I would imagine that any sensor issues that would cause performance issues would throw a code or two.
Generally, carbon fouled plugs indicate a weak ignition system or computer driven control issues. That it is bank-biased tells me that it could be the sensors.
Racer
Joined: Jul 2002
Posts: 466
Likes: 0
Have you cHecked your exhaust to see if there are any rust holes in it.
My dad's 89 has the left side exhaust missing right now and when you tap the gas it backfires each time, i removed the exhaust because of the rust.
My dad's 89 has the left side exhaust missing right now and when you tap the gas it backfires each time, i removed the exhaust because of the rust.
Thread Starter
Pro
Joined: Feb 2003
Posts: 540
Likes: 1
From: Taunton MA
the whole exhaust is less than a year old and is stainlee w/the exception of the headers.
Race Director
Joined: Sep 2005
Posts: 10,878
Likes: 1
St. Jude Donor '07
Did the headers move the position of the O2 sensor further 'down line?' If so, I think you need a heated O2 sensor to operate properly. It may not throw a code and will run the mix off. (So it was with my L98, anyhow.)
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Thread Starter
Pro
Joined: Feb 2003
Posts: 540
Likes: 1
From: Taunton MA
Are you getting any codes?
I'm not an LT1 expert, but I would imagine that any sensor issues that would cause performance issues would throw a code or two.
Generally, carbon fouled plugs indicate a weak ignition system or computer driven control issues. That it is bank-biased tells me that it could be the sensors.
I'm not an LT1 expert, but I would imagine that any sensor issues that would cause performance issues would throw a code or two.
Generally, carbon fouled plugs indicate a weak ignition system or computer driven control issues. That it is bank-biased tells me that it could be the sensors.
I did replace the o2 sensors a few years ago and it is showing some of the same signs of when they went bad the first time the only real diffence is the backfiring. The other thing that leads me to belive that its the o2 sensors is that i replaced them w/autozone replacements (money was alote tighter when i replaced them).
Thread Starter
Pro
Joined: Feb 2003
Posts: 540
Likes: 1
From: Taunton MA
yes they did move the location of the o2 sensors further away but i think that they are heated o2's from the factory because they are 4 wire.
Thread Starter
Pro
Joined: Feb 2003
Posts: 540
Likes: 1
From: Taunton MA
I Hate to be the one to ask, but do you have a FSM? You should be able to figure it out w/ one. I will say that it sounds like a injector problem. Try ohming each injector, I think LT1 injectors should be about 14 to 15 ohms.
I would try that first, just to make sure they are OK.
Randy
I would try that first, just to make sure they are OK.
Randy
Melting Slicks
Joined: Jul 2004
Posts: 2,018
Likes: 1
From: OR
Is it back firing through the intake or out the exhaust? Is there a mis-fire or loss of power accompanying this or do you just hear a popping sound? Does it happen on acceleration, deceleration, at cruise, or random?
Thread Starter
Pro
Joined: Feb 2003
Posts: 540
Likes: 1
From: Taunton MA
its backfiring throught the exhaust and there is a loss of power (car stalls out) i havent even driven the car on the road yet just moving it in and out of the garage.
