LT1 diagnostic help...
Thread Starter
Teching In
Joined: Nov 2008
Posts: 6
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LT1 diagnostic help... An old project of mine is back to haunt me.
It was brought in not running. The water pump had gone bad and killed the opti. I've got it back up and running, but...
Fires right up when cold, but it will only idle. Idle seems a little rough, but not a dead out miss. Move the throttle at all and it dies. Once it dies, a little difficult to get started again. I was able to fiddle with it a couple times and raise the rpm a few hundred before it choked but that's it.
I was positive it was classic MAF (looks like he's been running it without a filter and the screen is missing) but the replacement didn't change a thing. Now I'm thinking TPS but I'm also starting to throw parts at a problem I'm not sure of, and that gets expensive...
Any .02 is welcome.
Jeff-
It was brought in not running. The water pump had gone bad and killed the opti. I've got it back up and running, but...
Fires right up when cold, but it will only idle. Idle seems a little rough, but not a dead out miss. Move the throttle at all and it dies. Once it dies, a little difficult to get started again. I was able to fiddle with it a couple times and raise the rpm a few hundred before it choked but that's it.
I was positive it was classic MAF (looks like he's been running it without a filter and the screen is missing) but the replacement didn't change a thing. Now I'm thinking TPS but I'm also starting to throw parts at a problem I'm not sure of, and that gets expensive...
Any .02 is welcome.
Jeff-
Thread Starter
Teching In
Joined: Nov 2008
Posts: 6
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I have a scan tool, the owner had a fancy alarm and stereo installed and they moved the diag port (why in the ___ would they do that?). I've been digging through all the extra wiring and relays trying to find what they did with it.
I'd love to see the tps %.
The owner said it was running fine before the w/p crapped. As far as mods, it doesn't have any that I'm aware of. I don't think it has run in over a year.
Jeff-
I'd love to see the tps %.
The owner said it was running fine before the w/p crapped. As far as mods, it doesn't have any that I'm aware of. I don't think it has run in over a year.
Jeff-
Thread Starter
Teching In
Joined: Nov 2008
Posts: 6
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TPS seems to be working based on voltage output (.57 closed and rises like it should with throttle).
I finally found the ADL (diag port) but scan tool says it cannot make connection. I know that my scanner works on this, I bought it for this vehicle and used it several times and gave it to the new owner.
Any ideas welcome.
Jeff-
I finally found the ADL (diag port) but scan tool says it cannot make connection. I know that my scanner works on this, I bought it for this vehicle and used it several times and gave it to the new owner.
Any ideas welcome.
Jeff-
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Teching In
Joined: Nov 2008
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Too much info and folks seem to stop helping... It is a conversion
87 Astro with a 96 T/A engine. All stock except headers. An outfit in Texas did the harness for me 11 years ago (took the Astro harness from the firewall out and combined it with the T/A harness. I got sick of the opti dance and sold it 8-9 years ago. Been thru 2 owners since, they've gutted the tranny once and the rearend twice. Obviously, no one in town will touch it when it has a problem. He's been begging me for a year to look at it, I've tried successfully to forget all I know about LTs and now I'm suffering because of it...
Latest diag info...
I just happened to think about the fuel pressure, pulled the cap off and stuck a thumbnail on the schrader... nothing came out. I went and got the gauge and put on it, turned the key, hear the pump running, gauge doesn't move. I start it up, it will barely idle, still no pressure showing on the gauge. How can it even idle?
Looks like it needs a pump. G-d, what a nightmare.
Jeff-
87 Astro with a 96 T/A engine. All stock except headers. An outfit in Texas did the harness for me 11 years ago (took the Astro harness from the firewall out and combined it with the T/A harness. I got sick of the opti dance and sold it 8-9 years ago. Been thru 2 owners since, they've gutted the tranny once and the rearend twice. Obviously, no one in town will touch it when it has a problem. He's been begging me for a year to look at it, I've tried successfully to forget all I know about LTs and now I'm suffering because of it...
Latest diag info...
I just happened to think about the fuel pressure, pulled the cap off and stuck a thumbnail on the schrader... nothing came out. I went and got the gauge and put on it, turned the key, hear the pump running, gauge doesn't move. I start it up, it will barely idle, still no pressure showing on the gauge. How can it even idle?
Looks like it needs a pump. G-d, what a nightmare.
Jeff-
