I know that there are other threads here with my problem, I just figured it would be easier to start another. Anyways, here it goes:

F150 Heritage 4.2l V6 w/ 5 spd. manual running like crap, not even driveable. Got a P0174 (bank 2 lean) and an IAC circuit fault. Here's what I've done so far:

1. Changed plugs, wires, coil pack, fuel filter, plenum gaskets, isolator bolts, intake gasket, driver's side upstream O2 sensor, IAC valve, and EGR vac. solenoid.

2. Cleaned MAF sensor

3. Tested dpfe, EGR valve, and checked fuel pressure at the rail (38psi)

4. Sea Foam in the gas, and ran some through the intake.

5. Checked for vacuum leaks from one end of the motor to the other (to include brake booster), and can't find any.

6. Pulled the plugs to see what they are telling me, and they ALL appear to running on the lean side (all white, no brownish color to speak of, and not yet burned up)


Any suggestions? I can run a test on the MAF to see if it went ****-up, but this throwing money at it **** is starting to **** me off. I'm about ready to park it on the railroad tracks and walk away!

 

Come on, I need some help!!!!!!!!!!!!!!!!!

 

I feel your pain. Waiting on an answer to one of my questions too. Sounds like you have done a through check of everything but the injectors themselves. Just my 2 cents.

 

Not too many guys on here have a 4.2 v 6 so until someone that knows that engine sees this you might not get an answer.

I would check for vacuum leaks around the intake manifold. My leak is on the rear of the throttle body by the pcv hose/iac valve but I have the 5.4.

Good luck!

 

Get a can of spray Berryman B12 and with the motor idling warm, spray the sides of the intake where it hooks to the heads and see if you get an increase in RPM's. I'm betting the right side rear of your motor is sucking air. This seems to be where most of the 4.2 intakes leak. It is usually from intake bolts backing out and causing the intakes to leak. If you do find this to be your problem, spend the money and get the bolts from Ford to reattach it. You will be money and time ahead if you do. Sure they aren't cheap, but redoing the intake gasket a 2nd or 3rd time isn't either. Hope this helps. Good luck.