I drive a 1985 Fiero with a 4.9L conversion from the Fiero Factory. The following upgrades were added shortly after the install of the 4.9L:
• Vss signal connected to the Caddy ECM.
• Also had my MEM-CAL Chip reprogrammed by Fiero Addiction.
Fast forward several years and I had to have the injectors replaced, but another problem appeared and may be a coincidence.
The engine starts on fast idle (2000 Rpm) and drives normally with no stalling, but idles at 1200-1500 RPM. I have twice replaced the ISC motor following the adjustment procedure, replaced the ECM, checked and reset the TPS setting, checked for obvious vacuum leaks, cleaned the throttle plate, and ran several code scans, with no improvement whatsoever.
If you have any ideas or recommendations I would really appreciate your response