gjevela

Hello all, first time poster, long time reader and fan of these forums.

I have a 1999 F150 4.2l XLT 5 speed manual. Its been a good truck for many years but is now having some problems that I'm having difficulty resolving.

Last fall / winter I serviced the vehicle. Tore it down to the block and heads and replaced the following:

spark plugs
egr valve / gasket
DPFE hoses
intake manifold gasket
valve cover gaskets
air intake gasket
throttle gasket
water pump
pulleys / tensioner
drive belt
fuel injector o-rings
fuel filter
air filter
oil filter
oil
coolant
both heater hoses
all coolant hoses
pcv valve and hoses
battery

After putting it back to together I almost immediately got p0136, p0156, p1131 and p1151.

I took the vehicle to a local Ford dealership and they were just as confused about these codes. The HEGO's are stuck open and not switching. No vacuum leaks detected.

I replaced the HEGO's with Motorcraft from the Parts Department for good measure and am running a dry air filter now (for about 8 years I was running on a K&N oiled filter). I also cleaned the MAF sensor (same one used during K&N years) during all this work with CRC MAF cleaner. Still have the codes, still shuddering / stalling, and oddly when I start the vehicle from a cold start, it cycles through 3 near-stalls where it will drop from 900 RPM to about 200 RPM, 3 times before level'ing off.

Can anyone help me with this please.

TLB4

Found this on another site, and seeing as how you did a recent everything service, this seems like something you might want to look into.

Check into this issue.
TSB
05-22-6
ISSUE:
Some 2001-2003 F-150, 2004 F-150 Heritage and 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.


SERVICE PROCEDURE

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 PC/ED Manual.
Remove the upper intake and replace only the port gaskets (9H486) and isolator bolt assemblies (9S479). The new isolator bolt assemblies use a rubber 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.
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 NUMBER PART NAME
1L3Z-9H486-AA Port Gasket
3F2Z-9S479-AA Isolator Bolt


Source: http://www.fordf150.net/forums/viewtopic.php?t=51788

gjevela

Thanks for the input TLB... unfortunately I don't think that TSB applies to my model as my manifold is aluminum, upper and lower both. I cleaned both of them out with lacquer thinner and #0000 steel wool, including the EGR passages within the lower before putting it back together.

Torque'd them both down to spec listed in my Chilton's manual (I think it was 89 in. lbs.) with Permatex threadlocker.

I should have mentioned in my opening post, the reason I did all this service was because the SEL with those same codes have been on for a couple years and I decided to service the vehicle myself.

The stalling / engine bucking under load is more obvious now because the engine is cleaned out and not sluggish... making the emissions problem more obvious to me while driving.

Trying to interpret the OBD codes myself, I understand that these codes (1131, 1151, 0136, 0156) could either be an electrical circuit failure of the HEGO's OR could a fuel system problem causing the HEGO's to be stuck open. Someone please correct me if I'm wrong in my interpretation.

My only guess at this point is that it might be electrical, fuses or wiring, of the HEGO's (electrical) or possibly the diaphragm within the FPRC is stuck (rich mix) and needs to be replaced. There are no other DTC codes related to sensors that would feed information to PCM to adjust fuel trim levels.

If it's electrical related, like corroded wiring within the harness, wouldn't other components bundled in the wiring harness also have been effected? It just doesn't make sense to me that JUST the HEGO's within the harness would have gone bad and nothing else. And Fuse #23 looks good also.

gearhead88tc

has the issue gone away when you changed out the o2 sensors?

gjevela

Nope, the stalling / bucking, bad MPG were still there after the O2 swap, however.....

I MIGHT have just found my problem. Just got back inside, part of the wiring harness fell down and way lying on top of the EGR tube that runs into the pass-side exhaust manifold. Don't know how long that's been like that, but part of the plastic cover for the wire bundle was melted, so those wires were exposed to that EGR tube direct heat.

Pulled open the plastic covering the wires, I can't see any visible damage to the wires. Will get everything cleaned up and post update tomorrow.

gjevela

Its been a while since I posted last on this thread, but the problem has been resolved and no SEL since. Here's what the problem was: The smaller wiring harness that goes to all of the rear sensors was burned by the EGR elbow where it seats into the exhaust. There was 1 flimsy push-pin that held that entire harness off the exhaust, at some point it came out.

12 wires total in that bundle (4 wires per catalytic monitor (2), 2 wires in the VSS and 2 wires in that other sensor on the transmission that shuts the vehicle off (can't remember name)). I replaced 10 of the 12 wires with 18 gauge stranded wire and butt splice connectors. Used an entire roll of electrical tape to re-seal all the wires within the conduit.

It was a cheap fix, but meticulous as you have to clip and replace every wire that is burned or that you suspect might be burned.

For future reference for anyone that has P0136 and / or P0156, before doing anything else I would look CLOSELY to ensure that part of your harness has not fallen down near or on top of any part of the exhaust system.

I ended up having to remove the throttle body (upper plenum) to reveal everything. I also replaced the FPRC for good measure as I had P1131 and P1151. Between the harness fix and replacing the FPRC, we're all good to go.