Help!- 96 Explorer Very Bad Idle

[CynicsaurusRex]

My girlfriend has a '96 Explorer with a 4.0L engine. Starting last month the vehicle has begun to have a really difficult time running at idle. When I start I have to depress the gas and let it run for several minutes otherwise when I let it try to return to idle it will stall. Also when it is idling it will only idle very very low, at tops 500RPM. Last week the CEL came on so I took to an autozone to get the codes. They were a P0171 (too lean) and some other code for the IAC valve (I forgot the number). I picked up some electronic parts cleaner and popped the IAC valve off and gave it a good cleaning. After reinstalling the IAC valve and topping off her fluids the truck ran like a dream. Normal start up, easily returned to idle, and it drove without any hesitation. Fast forward two days and I am having the same trouble. The truck is having a hard time starting and will not idle when cold. Please any advice would be appreciated. I need to be able to depend on this truck getting her to work safely and reliably.

 

[CynicsaurusRex]

To add a little bit more to my conundrum, I found out today that her temp gauge isn't reading properly and it is taking a long time to get hot air in the cab. Could it all be linked to a thermostat being stuck open?

 

[devlin michael]

My girlfriend has a '96 Explorer with a 4.0L engine. Starting last month the vehicle has begun to have a really difficult time running at idle. When I start I have to depress the gas and let it run for several minutes otherwise when I let it try to return to idle it will stall. Also when it is idling it will only idle very very low, at tops 500RPM. Last week the CEL came on so I took to an autozone to get the codes. They were a P0171 (too lean) and some other code for the IAC valve (I forgot the number). I picked up some electronic parts cleaner and popped the IAC valve off and gave it a good cleaning. After reinstalling the IAC valve and topping off her fluids the truck ran like a dream. Normal start up, easily returned to idle, and it drove without any hesitation. Fast forward two days and I am having the same trouble. The truck is having a hard time starting and will not idle when cold. Please any advice would be appreciated. I need to be able to depend on this truck getting her to work safely and reliably.

 

[devlin michael]

last year my explorer idled poorly, long story short- burt brake light. short time later same low idle, turnsw out stuck thermostat keeps car in lean condition because it never reached norm operating temp, new thermostat cvured it that time. couple months ago same low idle returs with a friend, rough and low idle. had a short in my wiring harness that runs down pass side of intake. fixed that and windows stared working, 4x4 low and high lights quit flashing,dome lights also work. and idles perfect. great huh, bull****, transmission went out today.good luck with yours. best advise is sale, sale, sale,

 

[devlin michael]

hate your car

last year my explorer idled poorly, long story short- burt brake light. short time later same low idle, turnsw out stuck thermostat keeps car in lean condition because it never reached norm operating temp, new thermostat cvured it that time. couple months ago same low idle returs with a friend, rough and low idle. had a short in my wiring harness that runs down pass side of intake. fixed that and windows stared working, 4x4 low and high lights quit flashing,dome lights also work. and idles perfect. great huh, bull****, transmission went out today.good luck with yours. best advise is sale, sale, sale,

 

[swshawaii]

I picked up some electronic parts cleaner and popped the IAC valve off and gave it a good cleaning. After reinstalling the IAC valve and topping off her fluids the truck ran like a dream. Normal start up, easily returned to idle, and it drove without any hesitation. Fast forward two days and I am having the same trouble. The truck is having a hard time starting and will not idle when cold.

Sounds like you need a new IAC valve, OEM preferred. The p0171 lean code is probably unrelated. Any vacuum leaks?

 

[Flash]

I'd replace the IAC valve and check the thermostat.

If a thermostat fails open the truck won't get up to temperature and it will continue to run rich.

 

[CynicsaurusRex]

No vacuum leaks that I have found so far. That being said I haven't done the most thorough check yet. I'm wondering if I have two unrelated problems. The first being a faulty IAC valve causing the bad idle, and a open thermostat causing that low temp readings and lean code. Is this possible/probable?

 

[NeuroResid]

No vacuum leaks that I have found so far. That being said I haven't done the most thorough check yet. I'm wondering if I have two unrelated problems. The first being a faulty IAC valve causing the bad idle, and a open thermostat causing that low temp readings and lean code. Is this possible/probable?

How many miles are on the Explorer?

 

[lakelanier]

Just replaced my IAC valve on my 96 4.0 Problem gone

 

[CynicsaurusRex]

Just replaced my IAC valve on my 96 4.0 Problem gone

Were you experiencing a similar issue?

The thermostat stuck open will cause it to run rich? Our explorer is running way too lean. Its got ~150K miles

 

[Flash]

Were you experiencing a similar issue?

The thermostat stuck open will cause it to run rich? Our explorer is running way too lean. Its got ~150K miles

If the thermostat is stuck open the engine will run too cool and the ecu will instruct the injectors to run rich to compensate.

This can dilute the oil on the bores causing excessive wear and blowby can contaminate the oil.

 

[CynicsaurusRex]

Well I definitely believe that I need a new thermostat mainly due to the time the engine takes to warm up and the fact that there is never any warm air in the cab, but I'm not sure it's the root of my problem because the engine is running lean, not rich. Also the oil looks fine at the moment.

 

[lakelanier]

Were you experiencing a similar issue?

The thermostat stuck open will cause it to run rich? Our explorer is running way too lean. Its got ~150K miles

It was running rough at idle only and a code did come up showing it might be one of the issues. Cheap and easy to replace and it would be good to change with your miles.