I have a 1999 F-150 Regular Cab/Short bed with the 5.4 V* and 2 wheel drive. I have had a full tune up, the fuel injectors cleaned at the dealership and still have what feels like a rough idle when when in park and when in gear with the brake on. It has been suggested that it could be my motor mounts gone bad causing excessive vibration and not really rough idle. DOes anybody have any experience with this?

 

what was included in a "full tune-up"

 

be more specific. is it just rough? or are the RPM's fluctuating?

the 5.4 is famous for a few idle problem causing things that some dealerships just aren't sharp enough or up to dat to figure out. or they milk it so they can get you un-needed things like fuel injector cleaning!!

in modern engines with modern gas fuel injectors almost never get clogged!

famous 5.4 idle problem causers;

dirty/clogged IAC (Very very common)
bad/collapsed PCV elbow hose at TB
dirty MAF
old fuel filter
bad coil due to coolant leak (I believe it is #4)
need PCM reset once or twice a year and then let engine properly learn new idle pattern. (Don't reset and then just take off)
carbon build up in TB (do not use carb cleaner ever!!)

I might be missing something so hopefully some one will chime in.

Good luck-

 

In the tune up, they cleaned the fuelinjectors, replaced all spark plugs, cleaned throttle body, and replaced the #4 coil because it bad.

What is an IAC?

Thanks for everyones help.

 

Hey hmcq -

Sorry to bring up the old thread again, but a quick question or three for you.
1) What's the best way to clean the MAF?
2) How exactly does one reset the PCM and then have it re-learn the idle pattern? (I've never done this since new in 98)
3) Why can carb cleaner be used on the throttle body? (I cleaned mine with a rag and solvent, but I can't recall what solvent I used, probably WD-40 or Isopropyl)

I'm still trying to repair the intermittent rough idle when warmed up in gear, that gets temporarily fixed with a throttle blip. Got clean injectors, new plugs, clean throttle body, new IAC...

Thanks again for your patience and help.

Alan in NJ

PS: '98 F-150 automatic 4x4.

 

You clean the MAF VERY CAREFULLY! It has very small wires that get dirty.

The best way to clean them is with a q-tip and some alcohol. Or very carefully spray the wires with Brake Klean or Contact Cleaner.

The reason you aren't supposed to use carb cleaner is that the TB is coated with plastic and carb cleaner will remove it. The plastic is there to help prevent dirt/carbon/etc build up.

To reset the PCM disconnect the NEG batt cable then turn on the headlights to drain the back-up. after about 5-8 min turn the lights off hook the neg batt cable back up start the engine without touching the gas pedal and let it idle for atleast 5-8 min. (This is where it will "Learn" a new idle) then you must drive it for atleast 20 min. Go easy on it as it will shift funny and do some strange things as it learns it's new patterns.

Good luck-

 

Thanks again. Of course, I did this before seeing your post. I did have the battery cable off long enough (with the headlight switch on), and then let it idle about 10 minutes before taking a drive, but I didn't drive more than 20 minutes. Hmm - I guess I'll have to repeat it again in the morning before I head up to my sister's. I suppose that it'll be OK if the first start after reset is with the engine COLD!

All this is still in attempt to fix the intermittent rough idle in gear problem. I replaced the IAC last weekend, and replaced the PCV & hose tonight, and also cleaned the MAF with a spray of throttle body cleaner. Since the problem doesn't show itself regularly, only time will tell if this fixed it or not...