Hello, I have a 98 f150 4.2 v6 that idles around 1100 RPM during a cold start and then will drop to around 900 after it warms up. Is this typical or too high? And if so....is there anything I can do to get it back within a normal range? I am selling this truck soon, so any major repair would prob be out of the question. Thanks guys.

 

I'd start at the IAC, TPS, and MAF (Idle Air Control, Throttle Position Sensor, and Mass Airflow sensor.)

The IAC and MAF can be cleaned but I've personally never had luck with that, others have so I may be doing something wrong. :P IAC
TPS
MAF

I had bad luck with the autozone TPS's on my Ranger so I'd suggest getting the motocraft for that.

 

Try what Aragorn said. I'd start with the MAF.

No codes, right?

 

no codes. What am I doing...just spraying carb cleaner in them?

 

Electronic cleaner, carb cleaner will kill them.

 

I'd start with the PCV system. It's the most common problem with a high idle. Then the IAC. If it's IAC, you can hit them with something to see if the plunger is hanging. The 4two is just as notorious with PCV problems as the V8's. Yours takes an elbow (usually the problem) that is stocked at Auto Zone hanging in the help isle. Looks like this, -



BTW- Auto Zone has their own packaging, perhaps it's Dorman packaging. The one I posted is indeed the Ford part for your 4.2L. I'm not sure about the V6's, but when everything is running right with the V8's, warm idle should be between 725 and 730. Ford has it between 700 and 750 but right around 730 is perfect and these engines have a history of idling great in the past. So great and smooth it's how you can tell if there's problem.

 

I am assuming you mean to clean the MAF? Use a Q-tip and Acetone or Isopropyl Alcohol to delicately clean the two wires on the sensor itself. You'll need whatever torx bit or phillips it takes (two screws) to get it off.

Don't use the spray in MAF cleaner. It will leave a residue, and not be properly cleaned.

 

Yea that's the best way. The wires are tough, very hard to break those. I guess what you have to watch out for is snagging a rag while cleaning by hand. When I use to service mine I used in combination a Q-tip initially, soaked in isopropyl. Then used a eye glasses cleaning cloth (the very thin micro fiber type) wrapped around a q-tip to get any residual residue. Doing it this way wouldn't snag the wires since they can be wrapped tight around the q-tip.. The wires are wrapped around posts and just end. It's where they end on the posts that snag. The wire on both sides stick out and catch the cleaning rag.

Since I set my box up with a 100,000 mile nano fiber filter, I no longer have to service the MAF or air filter.....well it's been years. Since I converted in 2008 anyway. Dirt doesn't embed with those filters. It falls to the bottom of the box asa you cut the engine. When I ran a oiled element, it totally trashed the MAF and tube in no time. Was always cleaning the damn thing. What a gimmick that was. They seem to filter great at first, but it just doesn't last. Then there's all the maintenance and recharging correctly. A scam for sure lol.

Anyway that's a great way to clean them, by hand carefully. Every electronics cleaner I've used that says residue free never has panned out. The only way that could work is if it wasen't dirty in the first place and you would have to hit the contacts point blank and nothing else. The MAF cleaner hose down method especially can never work because you contaminate the fluid before it reaches the MAF. You chances of making the MAF even more contaminated than they were are better than doing them any good.

Sorry, went long on this one.