1986 2.9L Surging Idle/Stalling Issue
I've been fixing up this 1986 2.9L V6 Ranger and I've run into an issue I absolutely cannot figure out. The engine starts fine and idles at the correct RPM but short blips of the throttle will always cause it to either stall or switch into what seems like a different run mode in the computer where it absolutely cannot figure out how to manage the engine anymore.
In the first video you can see the engine idling, and running through higher RPMs and then settling back down to idle as I release the throttle cable connection. As long as the deceleration is gentle there is no issue. If you quickly blip the throttle the engine stalls as you see in the first video or it starts surging over and over as in the second video. It seems to get stuck in this other run mode and can't find its way back to a stable idle. If you turn the car off and restart it the engine idles normally again.
The only OBD code I get is 42 which is "(R) System rich – Fuel control", and the exhaust definitely smells like it's running rich. The only lead I can think of right now is that when I remove the spout connector and run the KOER test it does not report the 42 code, but I've had timing set from 10 BTDC to 12 BTDC and it will always report the 42 code when the spout connecter is in. Maybe some issue with the signals from the distributor?
I've done a mix of fixing actual problems and some blasting the parts cannon and it is definitely running way better than before but I can't get this particular issue figured out. Any help would be appreciated!
Parts replaced:
Throttle position sensor
Idle air control valve
MAP sensor
EGR solenoid
PCV valve
Crankcase breather
Spark plugs (replaced with Motorcraft)
TFI module
Ignition coil
Fuel injectors (one was leaking)
Fuel pressure regulator (Fuel rail would not maintain pressure, also related to leaking injector)
Fuel pump
Fuel sending unit (pump in gas tank)
Air charge temperature sensor
Coolant temperature sensor
Oxygen sensor
Tests / other work:
Vacuum leaks fixed, no other leaks found with smoke test
Cleaned and verified EGR valve function
All cylinders have good compression and are within a couple of PSI of each other
Tested coolant system for exhaust gasses (none)
Verified timing