Iveson

I have a 2003 F-150 4.2 L. When it is cold the truck cranks up fine. Sortly after, the idle RPM's flucuate rapidly between 800 and 1200, which I find annoying. I have changed the spark plugs and wires and cleaned the MAF sensor. Any suggestions as to other things to look at? It never stalls and the up and down idleing goes away once the temp gauge hits the "middle" mark. I'm puzzeled.

Thanks,

iveson2@***.net

transmaster

You have a very common problem which both the 3.8L, and the 4.2L V6's has for the years listed below. The first thing to try is to Clean your IAC (Idle Air Controller) and see if that doesn't fix the problem. The IAC is located above and just behind the throttle body. Use MAS cleaner, and brake cleaner to do it. Below is what the part looks like. However the problem can be more then just the IAC this V6 has a chronic with the Bolts holding the intake plenum down.

All of you out there with 4.2L V6 (2001- 2004) should replace the original bolts which has a black plastic sleeve which breaks down giving you a vacuum leak. The replacement part has a green plastic sleeve.

Below is a complete explanation of the problem.

http://sites.google.com/site/fordf15...P0171P0174-Fix

Here the TSB concerning the overall cause of this problem:


FORD:2001-2003 E-150, E-250, 2001-2004 F-150

This article supersedes TSB 05-17-3 to update the vehicle model years and issue.

ISSUE:

Some 2001-2003 F-150, 2004 F-150and 2001-2003 E-150/250 vehicles equipped with a 4.2L engine may exhibit the malfunction indicator lamp (MIL) on with diagnostic trouble codes (DTCs) P1131 and/or P1151 (system too lean bank 1 or 2). This condition may be due to leaking isolator bolts/port gaskets in the upper-to-lower intake manifold mounting area. This condition is sometimes intermittent and may not be apparent on a warmed-up engine.

ACTION:

Refer to the following Service Procedure.

SERVICE PROCEDURE

NOTE:THIS CONDITION COULD ALSO BE DUE TO WARM AND THE USE OF WINTER GRADE FUELS WHICH HAVE VERY HIGH VOLATILITY AND MAY BOIL IN THE FUEL LINES (VAPOR LOCK) DURING A SHORT HOT SOAK. OXYGENATED FUELS WILL AGGRAVATE THIS CONDITION. IF NON-OXYGENATED FUEL IS NOT AVAILABLE, USE MID/HIGH OCTANE FUELS WHICH HAVE LOWER VOLATILITY AND MAY HELP ALLEVIATE THE CONDITION.

1. Perform a self test. If DTC P1131 and/or P1151 are the only codes stored in the powertrain control module (PCM) proceed to Step 2. If any additional DTCs are present, follow normal diagnostic procedures found in the Manual.
2. Remove the upper intake and replace only the port gaskets (9H486) and isolator bolt assemblies (9S479). The new isolator bolt assemblies use a material that is green in color, do not install the old isolator bolt assemblies with the black rubber material. Do not replace any other intake parts or gaskets. Refer to Workshop Manual, Section 303-01 (In-Vehicle Repair; Upper Intake Manifold) for removal and installation procedure.
3. While the upper intake manifold is removed, check the exhaust gas recirculation (EGR) orifices that are pressed into each primary port of the lower intake manifold. If any of the orifices are plugged with soot, clean and unplug them with a pick and solvent.

PART NAME:
Port Gasket: 1L3Z-9H486-AA
Isolator Bolt: 3F2Z-9S479-AA

transmaster

Duplicate posting