New guy needs help with 96 4.0 idle problem

[bahamacop]

So sometimes the idle on my '96 Exporer (V6, 4WD) just drops down to about 500 and stays there. It drives fine, acceleration is good, but then again sometimes when I slow down to a stop the RPM's dip to under 500, then rebound quick to 500. Sometimes it'll idle at about 900. The check engine light has come on, and gone off. Usually it'll stay on a day or so. I ahve noticed that during these problems the battery meter will sink fairly low, but that may be a result of the low idle. The battery is a fairly new Die Hard.

I have put new plugs and wires in it (all Motorcraft) and cleaned the throttle body the best I could (without taking it off). the throttle body was pretty dirtied up. Don't believe it had ever been cleaned, it's got 135K miles on it currently.

Any ideas on what it could be? Eventually when I get a chance I will run it by someone that can read the code the engine occasionally produces, but I like to hear any ideas as to the culprit.

 

[alohamonte]

I have a similar problem and haven't been able to figure it out... I don't have a CEL and it doesn't stall out, but it will drop to 500 or so during braking to a stop. It will drop a bit further if I'm doing a sharp turn at low speed.

I replaced much more than you: IAC, TPS, MAF, Plugs, Wires, PCV, Fuel Filter, etc and problem persists.

I think it's a vacuum leak... I suspect the brake booster or upper intake gaskets. but I haven't been able to locate it yet.

 

[marragtop]

To baha: try cleaning or replacing the IAC.

To Aloha: I agree sound like a vac leak. Do a vac leak test.

 

[bahamacop]

I thought the same thing. Checked all the vacuum lines, they looked good. Checked and cleaned IAC and MAF sensor. I'll drive into town tomorrow and hook it up to a code reader, see what happens.

 

[bahamacop]

Well, read the code, bought the part, car runs like a top now. It was the IAC. A couple of things of note here- I cleaned it with mass air flow sensor cleaner when the problem popped up. It didn't look "clean", just cleaner than before. The new one came with a gasket, which my old one did not have when I removed it. Nor was there any sign of there ever being a gasket. Included a pic of the old one. I guess the good that came out of this was that I got to trace all the vacuum lines and check them.