My wifes 1992 explorer has serious idle problems. It will barely idle with out stalling. Then once it warms up it wants to go up to about 3000. The idle control motor has been replaced. It is real intermitent after it has warmed up, you could be sitting at a stop light and be at 600 rpm then it will shoot up to 3000 in no time flat. Please help!!

 

Vacuum leaks?

 

no vacume leaks

 

hmm

What has been checked on the vehicle so far? Make sure that it is tuned up first of all. Plugs/wires if needed/fuel filter/air filter, etc. It sounds like it is either air related, ie vacuum leak or unmetered air, or fuel related, ie fuel pressure, clogged filter, etc.

 

Oh, one other thing to check is the plastic tube that goes from the throttle body to the air box. Mine developed a rip in the fins of it by the air box. I used some Blue RTV to seal it up. Unmetered air could get in through a leak in the intake tube and cause some problems.

 

I guess i can tune it up this weekend and check the filters. I just don't understand how that can effect the idle. What about low compression on a cylinder? It does have that on #4.

 

That could be it. Start with the basics first when troubleshooting. It could be that it gets starved for fuel and then overcompensates which causes the idle to surge up.

 

I have a '93 explorer V-6, 4.0L that developed severe idle problems this weekend. I've owned this truck since new and never saw anything like it. Lots of smoke, rich smell, chemical (burnt match stink), lots of water vapor in the air, black soot on the ground at tail pipe with lots of condensed water too. (Weather's like in mid 20's so some water happens but this was excessive.) Idle was surging and almost stalled at lights. RPMs over 2500 was steady but still not right. Compression test passed all cyl. in 160-170 range cold. I checked and cleaned sensor connectors, cleared accumulated oil in vacuum line to fuel pressure regulator. Checked fuel regulator return flow. Thanks to the great posts on this forum (and Ranger forum), I learned how to read KOEO codes thru the CEL. MisterCMK is right basic maintenance first. My problem was vacuum leaks around the vacuum ports on intake manifold (rubber expanded from oil) and a bad MAF sensor. After fixing vacuum leaks, I reset computer (disconnected neg term. bat. for >20min.) and restarted engine. Ran KOEO test and got code 159 - MAF out of range. Replaced MAF - She's purring and I'm back on the road in time for work on Monday....damn; but really glad all you folks post to this site. Thanks