backfiring and breaking up off throttle
02-01-2006, 12:19 AM
#1
TECH Regular
Thread Starter
Join Date: Feb 2006
Location: Long Island
Posts: 471
Likes: 0
Received 0 Likes
on
0 Posts
backfiring and breaking up off throttle I've got a 95 T/A 6 speed w/ stock manifolds and cat, and a Borla Catback with the right side baffle removed..so the right side is basically wide open exhaust and the left goes through the muffler. The car (and cat) have about 80k miles.
when I let off the gas the car breaks up a lot and usually backfires a couple of times too. my buddy was driving behind me one time and he told me some flames were coming out too. I'm wondering if the old cat and free flowing catback have anything to do with the backfiring..weird backpressure? Or is it something else. The check engine light is on and it threw a code - something about low voltage to sensor, I dont remember which one I'll have to scan it again. Any ideas?
when I let off the gas the car breaks up a lot and usually backfires a couple of times too. my buddy was driving behind me one time and he told me some flames were coming out too. I'm wondering if the old cat and free flowing catback have anything to do with the backfiring..weird backpressure? Or is it something else. The check engine light is on and it threw a code - something about low voltage to sensor, I dont remember which one I'll have to scan it again. Any ideas?
Last edited by f50nut; 02-01-2006 at 12:24 AM.
02-01-2006, 10:50 AM
#4
TECH Regular
iTrader: (4)
Join Date: Mar 2004
Location: GSO
Posts: 483
Likes: 0
Received 0 Likes
on
0 Posts
its an occurance thats common on alot of trans am. i dont know weather or not its because of the cat or the free flowing exhaust. but i do no that my old trans am was running rich and doing it alot more. i thought maybe changing the o2s would help. it made the rich part stop but the popping kept going. the car ive got now has mid-tubes, ory, high flow cat, and straight pipes after that. no resonator or muffler. the only time it does it now is when the car is cranked cold and reved. i also took off the air pump off so that slows the heating of the cat. so what i drew from all of my experience so far is that the cat being cold with the exhaust flowing over it is what causes the popping and crackling. as for flames i dont know. let me know if you need anymore information.
02-01-2006, 01:40 PM
#6
TECH Regular
Thread Starter
Join Date: Feb 2006
Location: Long Island
Posts: 471
Likes: 0
Received 0 Likes
on
0 Posts
hmm, well it isnt running too rich...and I haven't noticed that it's better or worse when it warms up. I'll have to check out the cat, although the crackling isnt affecting performance
Trending Topics
02-01-2006, 04:59 PM
#8
Teching In
Join Date: Dec 2005
Location: Phoenix AZ
Posts: 45
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by 2fast97Z
same thing is happening with me but im running rich as hell and backfiring and cracklinng like no other but i just need a tune and ill be good
02-01-2006, 06:22 PM
#9
Banned
Join Date: Dec 2005
Location: pittsburgh,pa
Posts: 265
Likes: 0
Received 0 Likes
on
0 Posts
when i had stock manifolds gutted cats and a wide open borla it did the same thing(mostly when cold). replaced my cap,rotor, coil, plug and wires and it went away. it only does it when it cold now. i heard a lot of lt1's run real lean in the upper rpm range and a fuel regulator would correct it. also every lt1 i have driven backfired when it was cold. even if the all stock ones.
02-01-2006, 06:31 PM
#10
TECH Regular
Thread Starter
Join Date: Feb 2006
Location: Long Island
Posts: 471
Likes: 0
Received 0 Likes
on
0 Posts
i am very new to lt1's, doesnt it not have a cap and rotor - just the optispark?
for instance if i am to do a tuneup, obviously plugs and wires, and is there something i replace in the opti? mine does it even after it's warm
for instance if i am to do a tuneup, obviously plugs and wires, and is there something i replace in the opti? mine does it even after it's warm
02-01-2006, 07:17 PM
#11
Banned
Join Date: Dec 2005
Location: pittsburgh,pa
Posts: 265
Likes: 0
Received 0 Likes
on
0 Posts
it does have a cap and rotor. the cap looks like it's the whole thing but's not. one of the reason's you never about it because most people just replace the whole unit because of the amount of work involved. a cap and rotor from gm is like 130 bux. msd recently came out with a cap and rotor for a 150.00. msd just came out with a whole optispark unit thats billit and you can adjust the timing +/-7 degree's but i have no idea how well it works or how much it is. you can get a gm one from summit for like 250.00 for the 95-97. the 93-93 are more money.
02-02-2006, 10:39 AM
#14
TECH Regular
iTrader: (4)
Join Date: Mar 2004
Location: GSO
Posts: 483
Likes: 0
Received 0 Likes
on
0 Posts
if youre gonna get a new opti go ahead and pick up a hayness manual. thats proably one of the best things i did when i replaced mine. step by step telling you the easiest way to get it off. best thing to do is to take the fans out to get to the water pump. but will your down there you mite as well take the air pump off and cap the manifolds or headers off. save a little weight and frees up some space under the hood.
02-02-2006, 01:52 PM
#15
On The Tree
Join Date: Nov 2004
Posts: 119
Likes: 0
Received 0 Likes
on
0 Posts
Flames and backfires indicate unburned fuel.
1. Either the car is too rich, (not enough air to mix with fuel)
2. Or the plugs are fouled. Vicious cycle: Foul plugs cause misfire causing foul plugs.
3. Or bad/burnt wires causing misfires.
4. Spark plugs with wrong heat range.
5. Bad coil (usually symptoms show at low rpm or cruising.)
At higher RPM you have more air and fuel so it is more likely to burn. Most likely it is too rich at low rpm but that could be only part of what is wrong.
1. Either the car is too rich, (not enough air to mix with fuel)
2. Or the plugs are fouled. Vicious cycle: Foul plugs cause misfire causing foul plugs.
3. Or bad/burnt wires causing misfires.
4. Spark plugs with wrong heat range.
5. Bad coil (usually symptoms show at low rpm or cruising.)
At higher RPM you have more air and fuel so it is more likely to burn. Most likely it is too rich at low rpm but that could be only part of what is wrong.
02-02-2006, 10:10 PM
#16
TECH Fanatic
iTrader: (8)
Join Date: Oct 2005
Location: Holland Twp/Milford, New Jersey
Posts: 1,419
Likes: 0
Received 1 Like
on
1 Post
Assuming there are no mechanical problems, the car is definitely running rich. the flames are due to extra oxygen getting into the exhaust system somewhere, re-igniting the unburnt fuel (which means you have a leak). have someone plug up the tailpipes by holding a rag tight against both tips, and listen for a leak somewhere up the pipes (while the car is running, of course). it'll be easy to find, if you have a leak. definitely scan for codes for that indicating light. if you think it's the cat, take a temp reading just before and after using a thermal detector, or pyrometer, and the exhaust coming out should be hotter (at least 150 deg. difference). if not, your cat is bad. you didn't mention anything about misfiring, so your plugs/wires shouldn't be the case... you'll definitely notice if it's misfiring anyway, so I doubt that's the problem, considering you said the motor still runs strong. I hope this helps!
02-02-2006, 11:37 PM
#18
11 Second Club
iTrader: (4)
Join Date: Dec 2003
Location: FL
Posts: 553
Likes: 0
Received 0 Likes
on
0 Posts
It's normal....if the car runs hard, don't try to fix it. 
Oh, and if it's an O2 sensor code, then it's in open loop with a 15.7:1 A/F ratio. Pull the PCM fuse for a minute, pop it back in and see if it goes away. PCM fuse is in the interior driver side fuse block when you open the door.
Oh, and if it's an O2 sensor code, then it's in open loop with a 15.7:1 A/F ratio. Pull the PCM fuse for a minute, pop it back in and see if it goes away. PCM fuse is in the interior driver side fuse block when you open the door.
02-03-2006, 01:38 AM
#19
TECH Regular
Thread Starter
Join Date: Feb 2006
Location: Long Island
Posts: 471
Likes: 0
Received 0 Likes
on
0 Posts
already checked for the open loop - picked up a scanner over the holidays and flashed the computer a couple of times...tomorrow i'll go ahead and scan it again, check the plugs and find the exhaust leak. it does run hard but the sound pisses me off..