My 98 4.2 starts very rough and then the idle will immediately even out and has an uneven/surging idle at very low speed. I've tried everything suggested here with no luck.

Today I popped out the Intake Air Temp Sensor and wiped it with a Qtip and rubbing alcohol. I did bent it a bit, 1/8 inch, and pushed it back into it's original position and then reinstalled it. I also disconnected the battery to reset the computer hoping the idiot light would shut off. Now I'm the one feeling like an idiot.

I touched nothing else on the motor! I swear! I tried to start it and now it won't run. It will start but then immediately stall. If I goose the gas it will rev a bit, has a giant sucking/whistling sound, and then stalls.

I tested the connector, it's fine. I must have cracked the sensor wire itself when I wiped it. I read that the default setting on the sensor is -40 degrees with a range of -40 to 150 degrees. I thought if it won't run due to a broken sensor wire maybe it will if I jump the connector. Nope...same result. If it's fully choked you'd think it would smoke but it seems like it starved for gas and there's no smoke. I don't know.

It seems silly that something so small could shut the whole motor down. I'll be ordering a new IAT but in the meantime I have a fishing lodge full of guests. I'm on an island and it'll take a week to get the part flown in. Is there a way to bypass the sensor to get the truck running in the meantime?

Thanks in advance.....feeling like an idiot.

 

I would check for a loose vacuum hose. The PCV hose on my truck hooks up close to the IAT sensor. Also make sure your intake clamps are secure.

 

Cleaned the idle air control valve?

What are the codes if the CEL is on? That would most likely tell you exactly what is going on.

 

It's highly unlikely an IAT sensor will cause those symptoms. If in doubt, just unplug it and the PCM will substitute default values so as to keep running.

I'm going to agree with the recommendation to check for a massive vacuum leak.

 

I've been looking for a vacuum leak ever since I bought the truck, can't find one. Maybe I pulled the hard plastic vacuum line from the breather loose at the motor connection when I took the breather assembly off to wipe the IAT sensor. I'll check it again. Like I said, there is a giant sucking/whistling sound before it stalls.

The PCV valve is new and I put clamps on both ends. I did clean the IAC valve with a slight improvement. New one on the way. Someone said to clean the throttle body but there is a sticker on it that is quite clear and says not to clean because it has some special coating....so I didn't clean it.

I don't have a code reader here on the island and don't have access to one.

 

Yep, I am an idiot. My spark plug elbow that attaches to the manifold from the PCV popped loose. Runs good now. Slap me with a baseball bat.....