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205 Posts
Alright, been a while since I tore into my Trans Am to figure this out, but here is my car and situation :
1988 GTA with transplanted 1994 LT1/T56, running ****LTCC LS-Coil ignition system****. Ran fine for one year on normal opti, end of the season, original used opti I had failed, and I replaced it the following season and added LTCC and ran fine, then the issues started...two years ago. At the time I was putting it up for the winter, and it was a very fast transition from driving it every day, to it wanting to die out of no where. The car would randomly die, and if I was cruising, it would pop it's own clutch and keep going.
Getting it around to it lately, a few months ago, hooked up my laptop, got some data reports, and followed the results. I know the car was running rich for the two years, so wasn't surprised to see my O2 sensors were dirty, otherwise everything runs fine. Idles at around 750-800 rpms, throttle response is flawless, operates with an exhaust leak, but otherwise everything monitored like it was supposed to. The glitch was when it hit closed loop, it shut everything down like someone just shut the key off, no choking, no fighting to continue to run, just shut off. When it dies you do hear the fuel pump prime, again like someone flips the key off and back on. Which brings me to today.
I have tested/replace the throttle position sensor (old one was cracked badly around plug area), replaced O2s (carbon-ed up), replaced coolant temp sensor for fun, and using a sensor tester, tested the mass air flow sensor, but also tested a spare, tested map sensor, tested knock sensor. I also tested the hi and low resolution signals coming from the opti, and those are coming through clearly. Only sensor I haven't really tested was the idle air control valve, but again, it can hold a 7-800 rpm idle just fine, so I know that is working. Also replaced the fuel filter for precaution of it sitting for two years, and plan on doing oil change and filter, check tranny fluid condition/level, and if I can get my car running properly, getting an S60/drive shaft/clutch. As far as my diagnosis is going, process of elimination is leaving me the assumption my ECU is failing me, and it's the only thing I don't have a spare of to try. Can anyone elaborate any other tests I can do?
1988 GTA with transplanted 1994 LT1/T56, running ****LTCC LS-Coil ignition system****. Ran fine for one year on normal opti, end of the season, original used opti I had failed, and I replaced it the following season and added LTCC and ran fine, then the issues started...two years ago. At the time I was putting it up for the winter, and it was a very fast transition from driving it every day, to it wanting to die out of no where. The car would randomly die, and if I was cruising, it would pop it's own clutch and keep going.
Getting it around to it lately, a few months ago, hooked up my laptop, got some data reports, and followed the results. I know the car was running rich for the two years, so wasn't surprised to see my O2 sensors were dirty, otherwise everything runs fine. Idles at around 750-800 rpms, throttle response is flawless, operates with an exhaust leak, but otherwise everything monitored like it was supposed to. The glitch was when it hit closed loop, it shut everything down like someone just shut the key off, no choking, no fighting to continue to run, just shut off. When it dies you do hear the fuel pump prime, again like someone flips the key off and back on. Which brings me to today.
I have tested/replace the throttle position sensor (old one was cracked badly around plug area), replaced O2s (carbon-ed up), replaced coolant temp sensor for fun, and using a sensor tester, tested the mass air flow sensor, but also tested a spare, tested map sensor, tested knock sensor. I also tested the hi and low resolution signals coming from the opti, and those are coming through clearly. Only sensor I haven't really tested was the idle air control valve, but again, it can hold a 7-800 rpm idle just fine, so I know that is working. Also replaced the fuel filter for precaution of it sitting for two years, and plan on doing oil change and filter, check tranny fluid condition/level, and if I can get my car running properly, getting an S60/drive shaft/clutch. As far as my diagnosis is going, process of elimination is leaving me the assumption my ECU is failing me, and it's the only thing I don't have a spare of to try. Can anyone elaborate any other tests I can do?