1990 Ranger 2.9 Update and IAT sensor
Finally got some time to dig into the motor on my 1990 2.9. I bought it with 235k dead, replaced fuel pump and almost all EVAP hoses to make it run and pass smog.
Replaced the valve cover gaskets and oil pan gasket, the sources of all the leaking. Under the valve covers looked to be two banks of valve train in perfect condition. Cleaned the valve covers off and there they were, stickers with a manufacture date of 2001. The stock motor must have had a catastrophic failure (Im guessing overheating and kaboom) in 2002 and was replaced with a factory motor. Estimated mileage 120k miles roughly (half of the 235k on the odometer). HECK YEAH!
Pulled the intake and cleaned it out and the throttle body, tons of dirt in there. The oem air box was destroyed (plastic deteriorated) and it had been sucking some dirt. This is where all my problems were. The truck was throwing a code but I couldnt keep it running good enough to get the code out of it. After cleaning everything I replaced the IAT sensor and bolted it all back together and it runs freaking perfect! No more engine light (must have been that sensor...), no more stumbling, purs like a kitten and runs very strong.
Symptoms were hard cold starting, would run very very rough. But sometimes it was fine, other times it would warm up fine and then run crappy. Mornings it seemed to act different than in the afternoon, ambient temperature changes seemed to make it act different.
If your intake is dirtly at all, clean it and replace that IAT sensor if you havent already. Dont ignore this $17 sensor if your having these kinds of symptoms.
Looks like I wont be replacing this motor any time soon after all! : )