'02 T/A - random no start, dying, then 3000 RPM idle
03-30-2019, 09:46 PM
#1
'02 T/A - random no start, dying, then 3000 RPM idle I recently bought my first F-body. 2002 Trans Am LS1 M6 with 117k miles. New engine installed at dealer, Trick Flow Cam, LT headers, SLP exhaust. I have been dealing with an intermittent condition that has me pulling my hair out. The first time I noticed any issue, I was accelerating, and the car just lost all power for about half a second, then resumed accelerating. When I let off the throttle, the idle would not drop below 3000 rpm. I drove to my destination about 10 miles away, turned it off, and even when I started the car back up about 30 minutes later, it was still at high idle. The idle finally dropped to normal (~1000 rpm), and the issue did not occur again for a few weeks.
The next time I had any issue, I went to drive the car, and it would turn over, but made no effort to actually start. Turns out I had no power to the fuel or ignition relays. the starter would engage, but absolutely nothing to the relays that should be energized in RUN (underhood FRC 2). While I was trying to identify the problem, key still in RUN, I randomly heard all the relays engage, fuel pump prime, and coils hum. I turned the key to START, and it started immediately.
I decided to be bold enough to drive the car a few days later and it repeated the brief loss of power, followed by 3000 rpm idle, then about 3 minutes later, it just died in the middle of driving 55mph on the highway. I left the key in run and persistently tried to clutch start the entire time it was coasting to absolutely no avail. After I came to a stop beside the road, I tried turning the key repeatedly from OFF to RUN listening to relays and fuel prime, but absolutely nothing. I had the car towed home, left it to sit for few days, and it started again beautifully and drove without a hiccup.
Today, I installed an Optima red top battery and changed the ignition switch (not the key cylinder, but the actual switch on the column) hoping that would resolve the problem, as the symptoms seemed to fit, but the car still cuts out and idles at 3000 rpm, so it appears to have done absolutely nothing to address the problem. Any idea what else this could be? Losing a ground? Any logical points of failure in the wiring harness apart from the ignition switch? Really bizarre VATS issue?
Additional info: No relevant OBD2 codes, speedometer randomly bounces all over the place while otherwise driving fine. all gauges randomly go dead and SERVICE VEHICLE and CHECK GAGES lights come on for about 2 minutes at a time (speedometer just goes back to bouncing all over). Cruise control has not worked since I bought the car, TCS OFF light ramdomly comes on, and touching the switch does not always toggle TCS back on. I have to assume these electrical problems are likely related.
The next time I had any issue, I went to drive the car, and it would turn over, but made no effort to actually start. Turns out I had no power to the fuel or ignition relays. the starter would engage, but absolutely nothing to the relays that should be energized in RUN (underhood FRC 2). While I was trying to identify the problem, key still in RUN, I randomly heard all the relays engage, fuel pump prime, and coils hum. I turned the key to START, and it started immediately.
I decided to be bold enough to drive the car a few days later and it repeated the brief loss of power, followed by 3000 rpm idle, then about 3 minutes later, it just died in the middle of driving 55mph on the highway. I left the key in run and persistently tried to clutch start the entire time it was coasting to absolutely no avail. After I came to a stop beside the road, I tried turning the key repeatedly from OFF to RUN listening to relays and fuel prime, but absolutely nothing. I had the car towed home, left it to sit for few days, and it started again beautifully and drove without a hiccup.
Today, I installed an Optima red top battery and changed the ignition switch (not the key cylinder, but the actual switch on the column) hoping that would resolve the problem, as the symptoms seemed to fit, but the car still cuts out and idles at 3000 rpm, so it appears to have done absolutely nothing to address the problem. Any idea what else this could be? Losing a ground? Any logical points of failure in the wiring harness apart from the ignition switch? Really bizarre VATS issue?
Additional info: No relevant OBD2 codes, speedometer randomly bounces all over the place while otherwise driving fine. all gauges randomly go dead and SERVICE VEHICLE and CHECK GAGES lights come on for about 2 minutes at a time (speedometer just goes back to bouncing all over). Cruise control has not worked since I bought the car, TCS OFF light ramdomly comes on, and touching the switch does not always toggle TCS back on. I have to assume these electrical problems are likely related.
04-04-2019, 01:44 PM
#2
Update for anyone having this problem in the future. It was a grounding issue. I found the grounding bolt on the rear of the driver's cylinder head to be loose, so the three wires landing on it were making intermittent connection. I tightened the bolt, and the dying/no start/high idle resolved completely. The gauges also no longer go haywire, and I have not had any issue with TCS since.
Cruise control is still inoperable, but I will diagnose separately. HTH the next person.
Cruise control is still inoperable, but I will diagnose separately. HTH the next person.
