'95 Ranger intermittently stalls out

[dave_enns]

1995 Ford Ranger XL 4 Cyl 2.30L

Engine intermittently stalls out. more often, during cold weather

My boy's first truck...trying to make it reliable! In these colder mornings, the engine will intermittently stall out. It happened during last winter...thought we fixed it as it didn't happen in spring, summer, fall (in CA weather).

TEMPERATURE - Doesn't happen during engine warmup process, but even when the dashboard shows good engine temp (while driving), it intermittently goes into a rough idle. I keep on gas and it will stay alive, but with no power. I come off gas and it will stall. However, by late AM through PM, it operates totally fine.

IDLE DESCRIPTION: Hard to diagnose, because it can be fine in all gears/speeds, but when it goes funky, it stays there until a stall. I need to wait a few minutes before it will successfully restart. It can run fine for a good amount of time, but something seems to trigger it into this intermittent stall out. Maybe a computer or sensor glitch is changing the mixture or maybe oil is getting in there and causing it to be weird.

No codes are happening now, but a few had led to these things being serviced:
ATTEMPTS – Auto shop couldn't diagnose...because the truck didn't stall out for them. They did find a few EGR lines to replace as some vacuum leakage was happening. Continuing with my own research: I replaced these sensors: IAC, MAF. Carb cleaner + wipe out the back of air intake. New air filter, fuel filter. Several of these seemed helpful to performance, but didn’t fix the problem.
My latest discovery was some oil in the large air hose inbetween air filter and the intake. Cleaned out and replaced the PCV. Oil has come back into this area. Next steps? Compression test? Other? But yet, why would this intermittent problem happen during cold weather but be fine for Spring, Summer, Fall?

Any ideas?? Thanks so much!

[shorod]

Because there does seem to be an ambient temperature correlation, I'd first check the function of the Intake Air Temperature (IAT) sensor and the Engine Coolant Temperature (ECT) sensor. It's possible the IAT sensor is integrated in with the MAF, but I think that became more common after 1995.

I recall the 2.3L Ford engines had quite a problem with Ignition Control Modules being temperature sensitive and causing stalling, but they generally acted up more when hot which should have still happened in the Spring and Summer. Similarly, the Crankshaft Position Sensors would commonly cause stalling, but they were less intermittent.

-Rod

[dave_enns]

Shorod,
Thanks so much for the tips, I will check both the IAT and ECT sensors. Once I get some conclusive thoughts, I'll reply. Hoping to find the solution!