Hoping to revisit this 7 years later LOL. I actually sold the truck after having a baby and immediately regretted it. I bought it back from the guy I sold it to last year, and I'm trying to fix this issue correctly.
The PO taped up the FIAV/ISC bypass passage inlet in the throttle body, just to get it driveable. I took out the tape, and want to fix it correctly. At cold start, the engine is at 1500RPM but will eventually climb up to 2200RPM and will stay there. I have checked:
- Engine Coolant Temp sensor tested within spec
- Idle Position Switch adjusted per FSM
- TPS tested and adjusted per FSM
- FIAV port sealed off
- Smoke tested, and no vacuum leaks
- Idle screw on throttle body closed all the way
- ISC replaced with new
Tried to adjust base idle speed per FSM by grounding ignition timing adjusting connector on firewall and #10 on the diagnosis connector in the glovebox (per FSM procedures) but adjusting screw is all the way in and RPM has no discernable difference.
I replaced the original ISC that tested out of spec, with a new Standard AC99 (black housing) that tests within spec (35-40s ohm). I also replaced the ISC harness that was cracking, and tested 0.2ohm resistance all the way to the ECU for all 6 wires. I opened up the ECU and no caps are leaking, but went ahead and preemptively replaced two caps, and there are no traces of leaks or burns of any kind anywhere in the ECU. I am certain the ISC is either not working or not getting the correct signal because I tested with the old ISC manually rotated it to the closed (furthest) position with the harness disconnected, and the RPMs were super low, which is basically how the PO had it with both ISC and FIAV ports blocked off manually. So basically, the ISC is allowing too much air through, but everything checks out.
I gave up and went to C&A in Van Nuys to get an opinion and he mentioned to get the throttle body rebuilt. Would rebuilding the throttle body address my high idle issue?? What would you do in my position? Can anyone enlighten me if I missed anything before I start throwing more money at it?
