Need help
Thread Starter
Junior Member
Joined: Dec 2004
Posts: 3
Likes: 0
From: Pflugerville, TX
Car: 89 GTA
Engine: 5.7
Transmission: automatic
Need help
My cousin is working on my 87 GTA 350 AUTO. At high RPM the car has a backfire. Here is the post from another forum. Any ideas would be apreciated.
Well Berts car hates me..........
Yesterday I borrowed Waynes scanner so I could see what the various sensors were seeing. All looked good. Swapped the MAF and the TB. no help. Wayne suggested I swap the distributor since I had a spare to rule out module and pickup coil. Today I removed the plenum and runners and installed the 87 style runners and plenum I have for the Z. the 88 and older car have a vary different idle air circuit. No help. I put the distributor for the Z in. the ignition module was cracked in it so I got a new one. No help. When I got the car running a few weeks ago the first sign of trouble was a miss at high RPM and then a dead hole when I went back to idle. I am not sure if that issue is part of the backfire issue or not but now the dead hole happens after the car has run for about 1 minute if the motor is cold when I start it. If the motor is at operating temp then the hole is dead as soon as it starts. I have pulled the plenum and runners again. replaced the injectors and EGR valve. Will test it all again tomorrow. If this does not help the only thing left is the wireing. so I might end up pulling the entire harness out of the car and looking for issues.
Thanks in advance for any help.
Bert
Well Berts car hates me..........
Yesterday I borrowed Waynes scanner so I could see what the various sensors were seeing. All looked good. Swapped the MAF and the TB. no help. Wayne suggested I swap the distributor since I had a spare to rule out module and pickup coil. Today I removed the plenum and runners and installed the 87 style runners and plenum I have for the Z. the 88 and older car have a vary different idle air circuit. No help. I put the distributor for the Z in. the ignition module was cracked in it so I got a new one. No help. When I got the car running a few weeks ago the first sign of trouble was a miss at high RPM and then a dead hole when I went back to idle. I am not sure if that issue is part of the backfire issue or not but now the dead hole happens after the car has run for about 1 minute if the motor is cold when I start it. If the motor is at operating temp then the hole is dead as soon as it starts. I have pulled the plenum and runners again. replaced the injectors and EGR valve. Will test it all again tomorrow. If this does not help the only thing left is the wireing. so I might end up pulling the entire harness out of the car and looking for issues.
Thanks in advance for any help.
Bert
Joined: Sep 2005
Posts: 27,918
Likes: 2,448
Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
What does the spark plug in the dead cyl look like?
Checked for broken valve springs?
There's no ONE WIRE that works ONE CYL, except for the spark plug wires. Therefore, there's NO WAY that anything in the "wiring harness" can do that, or that you can fix it by dinking with the harness. I'd leave the wiring alone, and do some basic troubleshooting instead.
You're welcome. Any time.
Checked for broken valve springs?
There's no ONE WIRE that works ONE CYL, except for the spark plug wires. Therefore, there's NO WAY that anything in the "wiring harness" can do that, or that you can fix it by dinking with the harness. I'd leave the wiring alone, and do some basic troubleshooting instead.
You're welcome. Any time.
Thread Starter
Junior Member
Joined: Dec 2004
Posts: 3
Likes: 0
From: Pflugerville, TX
Car: 89 GTA
Engine: 5.7
Transmission: automatic
Originally posted by sofakingdom
What does the spark plug in the dead cyl look like?
Checked for broken valve springs?
There's no ONE WIRE that works ONE CYL, except for the spark plug wires. Therefore, there's NO WAY that anything in the "wiring harness" can do that, or that you can fix it by dinking with the harness. I'd leave the wiring alone, and do some basic troubleshooting instead.
You're welcome. Any time.
What does the spark plug in the dead cyl look like?
Checked for broken valve springs?
There's no ONE WIRE that works ONE CYL, except for the spark plug wires. Therefore, there's NO WAY that anything in the "wiring harness" can do that, or that you can fix it by dinking with the harness. I'd leave the wiring alone, and do some basic troubleshooting instead.
You're welcome. Any time.
Well the GTA is fixed. I fould 2 of the 4 wires from the distibutor to the PCM were cut almost in half and freighed very bad. Must have been causing a noise in the advace retard signal. Fixed them and the car runs great.
about 30 plus hours of TS time and energy into finding 2 bad wires in the wire harness at the very back of the motor.