i have a 1999 f-150 super cab 4.2l. my truck runs fine when i am driving around, but when i stop and let it idle for a few minutes the truck shudders real bad and starts to idle real bad. i took it to auto zone and checked on their computer it said "bank 1 too lean, bank 2 too lean". i also took it to a ford dealership and used their computer. they said my fuel pump was bad and i needed an oxygen sensor (sensor 2). i replaced both of those items plus 2 more o2 sensors plus a complete tune up. it still does it. i have to replaced one more sensor (passenger side - after converter). someone told me it be a M.A.P.P. sensor. i am tired of buying parts to solve my problem. someone please help me!!!!!!

 

Check for vacuum leaks.

 

David,
Did your tuneup include new plugs and wires?
These are known culprits in situations like you describe.

 

we don't have Mapp sensors.

Who did the tuneup? You or a tune up place? I bet they didn't gap the plugs correctly.

Also, you could be running lean if your injectors are dirty. Too much air, not enough fuel. Try running some fuel injector cleaner through the tank.

Mass air flow sensor may need a shot of electrical cleaner, especially if you're using a K&N oil filter.

How many miles on your truck?

Tom

 

Actually, its not Tune Up, its Two Nup. That's the proper term. Also, try what everyone above has already said.

let us know how it works out!

Armand

 

i haven't checked for vacuum leaks yet. hope that isn't the problem. i changed all the plugs, plug wires, switched to a k&n replacement filter, fuel filter, oil filter, oil. i spent 300.00 bucks on everything. i have tried the fuel injection cleaner, no effect. i didn't check the plugs, they were supposed to be pre-gapped. maybe i should check that. and by the way, a 1999 f-150 DOES have a M.A.P. sensor. (Manifold Air Pressure sensor) page 4-14 chilton's repair manual. taking my truck to a repair place to get the injectors cleaned is my next step.

 

Any loss of power?

 

no, no loss of power or of fuel consumption. i still get 14 mpg's.

 

Any updates on your idle problem. I have a 97 4.2 with 112,000 miles that does the same thing. I have changed the spark plugs, wires, fuel filter, air filter, cleand the MAF and cleaned the IAC. My trucj still shudders form time to time when idleing. After reading through this forum i think i will replace this IAC. If you check for vacuum leaks, I would like to know how you did that. I do not know where to begin to check for leaks.

 

I think someone has mentioned that the plugs come gapped somewhere at like 0.45 or whatever, but the truck actually calls for 0.54 or something of that sort. Not exactly sure, but the haynes/chilton's manuals go over the proper gapping. Even the motorcraft plugs, to my understanding, come pre-gapped at a different gap then what is called for.

Anyone here know the answer? I haven't had to change my plugs yet.

Rman

 

The real answer is they come gapped at .040 and need to be re-gapped to .052 - .056.

If you had any vacuum leaks, especially in the evap department, you should throw a code. But you can still check for them by crawling around inside there and looking for cracked tubes and signs of deterioration. Also, check your PCV valve as well. Kind of hard to get to unless your sitting on top of your motor but it's just a buck or two to replace.

Tom

 

Honey, I Shrunk the Kids comes to mind.....

 

Yeah I wish. Then I could crawl into one of my cylinders through the sparkplug hole and try to figure out where that darn carbon buildup is and freakin' clean it off with a tiny airhammer.

 

no, no update yet. someone makes a vacuum leak detector kit. don't know who though. just seems funny that it runs good. just idles bad after about 2 minutes. i did change the pcv valve though when i did the tune up. i thought it might be the map sensor. called my local ford dealership and they can't find one on the 4.2. says it's only on the 5.4. so that option is out. about to take it in to the dealership and let them handle it.

 

I also experienced the same problems. I just cleaned the MAP sensor with a brake cleaner. Let it dry for a couple of minutes and it seemed to have worked.