Posting for a friend, need help with an 88 GTA
Thread Starter
Joined: Oct 2001
Posts: 646
Likes: 1
From: Sedalia, MO
Car: 1991 Z28 convertible
Engine: 305 TPI
Transmission: TH-700R4
Axle/Gears: 3.73 posi 4th gen 10-bolt
Posting for a friend, need help with an 88 GTA
Buddy of mine has an 88 GTA with a 305 TPI/auto. I feel bad for him because he got the car a while back and is in complete love with it, but he's really getting frustrated with it, and the more I think about it, I am too.
The car has never run 100% right. We tinkered with it a bit and set the TPS per the service manual, along with the timing. A tune-up was also done on it. He just had the plenum and runners off it, and added an adjustable fuel pressure regulator. We set the fuel pressure per the service manual.
The stupid car has this real bad chugging up until you hit about 3K RPMs. I had an 88 camaro the previous owner installed an 85 305 TPI in, and really goobered up, but heck even that thing didn't chug like this. We have checked the firing order, and the wires (which are new) to ensure there was no arcing in case one got too close to a manifold and the coating burned off. None of that is present.
Only thing we haven't done yet is check the IAC, which we have never messed with, and are almost certain is not the issue.
What we know was done to the car is as follows:
MSD coil
MSD ignition control box (6AL i think)
airfoil in TB
Accel replacement fuel injectors (19#) that came off my 85 TPI
adjustable fuel pressure regulator
Car had some ADS aftermarket chip in it, in fact I think it still does. Is it possible the ECM or PROM has dumped and is no good anymore? We spent a good part of the morning fooling with the MAF, we even checked the wire at CKT 998 (IIRC) and it checked out good.
I have experience working on TPI cars, both MAF and SD, and the only other one I've ever seen that ran this bad was my 91 Z28 after heads and a cam, and all it took was a timing adjustment to fix that...
Timing is set at 2* BTDC, which was as close as we could get it. I know these cars can be picky sometimes as to the timing, could this be an issue, and we need to advance it more to 6* or 8* to smooth it out? Any help is appreciated, thanks!
The car has never run 100% right. We tinkered with it a bit and set the TPS per the service manual, along with the timing. A tune-up was also done on it. He just had the plenum and runners off it, and added an adjustable fuel pressure regulator. We set the fuel pressure per the service manual.
The stupid car has this real bad chugging up until you hit about 3K RPMs. I had an 88 camaro the previous owner installed an 85 305 TPI in, and really goobered up, but heck even that thing didn't chug like this. We have checked the firing order, and the wires (which are new) to ensure there was no arcing in case one got too close to a manifold and the coating burned off. None of that is present.
Only thing we haven't done yet is check the IAC, which we have never messed with, and are almost certain is not the issue.
What we know was done to the car is as follows:
MSD coil
MSD ignition control box (6AL i think)
airfoil in TB
Accel replacement fuel injectors (19#) that came off my 85 TPI
adjustable fuel pressure regulator
Car had some ADS aftermarket chip in it, in fact I think it still does. Is it possible the ECM or PROM has dumped and is no good anymore? We spent a good part of the morning fooling with the MAF, we even checked the wire at CKT 998 (IIRC) and it checked out good.
I have experience working on TPI cars, both MAF and SD, and the only other one I've ever seen that ran this bad was my 91 Z28 after heads and a cam, and all it took was a timing adjustment to fix that...
Timing is set at 2* BTDC, which was as close as we could get it. I know these cars can be picky sometimes as to the timing, could this be an issue, and we need to advance it more to 6* or 8* to smooth it out? Any help is appreciated, thanks!
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Joined: Aug 1999
Posts: 2,842
Likes: 6
From: Rowlett, TX
Car: 1988 GTA
Engine: 5.0 TPI
Transmission: T5
Axle/Gears: 9 Bolt, 3.45
Re: Posting for a friend, need help with an 88 GTA
Do you get an SES light, or any codes from the ECM? The 86-89 ECMs are flaky and trouble prone, I have 2 of them with bad solder joints that cause random problems. One of them goes into limp mode, the other one the TPS doesn't read right. If all else fails, it could actually be a bad ECM.
Thread Starter
Joined: Oct 2001
Posts: 646
Likes: 1
From: Sedalia, MO
Car: 1991 Z28 convertible
Engine: 305 TPI
Transmission: TH-700R4
Axle/Gears: 3.73 posi 4th gen 10-bolt
Re: Posting for a friend, need help with an 88 GTA
yeah we keep getting a code 34...the maf is new, btw. we're gonna get a new ecm today and check that out.
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