Rough idle, And dying.

[4.0Rerolpxe]

I have a '93 4.0 X, and after i've been around town on warm days, stopping and going, when I start it up it tends to sputter and idle roughly, but when you get going it runs fine. On hotter days, after you've been around town when you go to start it, it will just go dead, to get it running you have to give it gas, enough to get it up around 3k rpms, then it tends to run normally again. It doesn't seem to have a correlation to engine temp. And i've replaced my IAC, and my Air Charge Temperature Sensor, but to no avail. Help please.

 

[doonze]

Mine was doing the same thing, but only when I was running it VERY hot (like hotter then L on temp gauge), Both times I've gone over L it's acted exactly like that when I tried to start it after shutting it off. I wonder if you may not be overheating but for some reason the under hood temp is getting hot enough to boil the gas. Old carb cars could have a problem like that if they ran too hot. Are you SURE your temp gauge is correct? Like I said I had the EXACT problem you had, but both times it was running really hot, didn't boil over just hot.

 

[4.0Rerolpxe]

Normally i run b/t R and M, but i do get hot alot during the summer, what was the solution to your problem?

 

[doonze]

LOL, mine is ongoing!

http://www.explorerforum.com/forums/showthread.php?t=246423

http://www.explorerforum.com/forums/showthread.php?t=245108

These are the treads about that, the 2nd one I kinda hijacked from someone else, so I started my own....

I'm determened to get my temp back into line! One way or the other!

 

[MrShorty]

I'd probably start with some basic diagnostics: pull codes from the computer, even if the CEL isn't on (some problems don't always trigger the CEL to light up). It's easy and only takes 5-10 minutes.

I'd probably also check fuel delivery. Check the vacuum line to the regulator for gasoline (gasoline=bad FPR). Put a fuel pressure gauge on it and make sure the pressure looks right at idle.

Check for vacuum leaks and missing/disconnected vacuum lines.

 

[924dr4x4]

when my old one ran hot,i put an external fan next to the tranny cooler and on a 90+ day with alot of humidity the temp guage never climbed past the r

 

[appletonbill]

Maybe cleaning your MAF might help. I think there is a sticky somewhere on this site to show you how.

 

[4.0Rerolpxe]

Thanks all for the suggestions, i'll let you know how it turns out.

 

[kingchicken318]

Probably the MAF, unplug it while its running. Your CEL should come on and the ECU will run it on defaults. Should smooth out the idle from a cold start. It could also be a fuel delivery issue like previously stated. I have a leaking fuel line and that is exactly how it acted when it was pissing out fuel above the back drivers side wheel.

 

[TedJ]

Maybe a possible vacuum leak somewhere? Check that the cap on the unused vacuum port on the tree has not fallen off, and just give all the lines a visual check.