For the past few months after the truck would heat up a little, the rpm's would drop to about 500 or 600 and idle rough. This happens while its in park and also while in gear. Occasionally it will die. I have 75,000 miles on it right now. I replaced the fuel filter back at 65,000 and just last night, I replaced all plugs and wires, thinking that this would fix the problem. Well that didn't fix it. I still have the rough idle at those low rpm's. I've been told to check the IAC but since I'm not getting a CEL light, it shouldn't be a sensor. Should I check this and how do I check the IAC? Is there something else I am missing? Should I check for a vacum leak around the intake manifold? Thanks for any help.

 

hope someone knows what's happening cause i have the same problem with the 4.0L in my explorer

 

Vacuum leak.

In my case, it was in the EGR line, right where it passes under the upper radiator hose. There's a little right-angle elbow there made out of reinforced rubber (that apparently tends to rot away after a while). Just pull the upper radiator hose out of the way and visually inspect it... on my truck, it was quite obvious. The part is not available at a standard auto parts store, but it's only around $30 from the dealer, and is the entire EGR assembly (not just that little rubber elbow). Takes all of 10 minutes to install.

My truck was performing exactly as you describe, above... and now it's running like a champ. Give it a check, and see if that's where your problem is...

 

Thanks, I'll check that out and see what it looks like.

 

That is not the EGR line, it is the PCV tube. Specifically it is the PCV elbow that disintegrates and causes the vacuum leak. I was able to find a silicone elbow that could be used instead of replacing the entire tube.

 

ah, okay.. thanks for the clarification. a car mechanic, I am not. ...but I can read a flowchart and follow directions. :D

 

If you can turn a wrench your halfway there.

It seems that PCV finds a way to wiggle out of the intake tube as well. I always check it in the summer since that seems to be the only time it happens.

 

Had the same thing happen to mine. Quick, simple fix that doesn't cost a fortune.

 

Had the same problem with the elbow breaking, paid the dealer 26 for both elbows and the 90* hose and fixed the problem

 

Cams, somebody must have swapped in some cams when you asleep one night! haha! J/M. Prolly a vaccum hose, had the same problem with my 302 in my other ranger. It was a vaccum line off on the MAP sensor.

 

Could you snap a quick photo when you get a chance, at the hose your talking about? I looked any my hoses look fine but with all the hoses and wires, I'm a little confused on the one your talking about.

Thanks.

 

If you do a search under "PVC elbow" you will find a thread I started. I posted pictures of that elbow.

 

Thanks. Thats what I was looking for. Now to check that elbow and see if its causing the problem.

 

Well I checked that hose and it seems fine. I didn't see anything wrong with it and there was no holes or cuts in it. Could it be a faulty IAC or MAF even though I'm not getting a CEL?

 

After reading this thread I went outside to my truck which had exactly this problem and my pcv elbow was shredded. I used rescue tape and tape the holes shut and my truck is running great! I also cleaned the MAF sensor and the throttle body plus put 3 zip ties on the throttle cable to get rid of the slack near the pedal and my truck is doing fantastic. Thank you guys for putting this up!