okvallier

This thread might be interested in this fix

https://sites.google.com/site/fordf1...P0171P0174-Fix

forayzor

Good find! Replaced more intake gaskets on 3.8s and 4.2s than I can count

am1

I'm having the exact same problem w/ my 4.2 ('01 w/ 73k). SES Light started coming on back in Sept. I immediately changed the plugs, air filter, oil and filter, cleaned throttle body and MAF sensor. Light stayed off for about a month, then re-appeared. Not being as savvy as most on this thread, I changed gas brands and octane level and ran a can of seafoam thru the tank and reset. Again, light stayed off for about a month, then came back. This has gradually whittled down to coming on once a week, now twice a day, or shortly after I reset. I let Oreilly's do a code check and I got the identical code (EGR flow insufficient). The clerk told me to try a can of seafoam thru the vac lines and then changing gas caps. Neither of those worked. So just for my clarification, a cleaning of your EGR and DPFE seemed to do the trick?

An un-related problem (or maybe not). The truck seems to jerk occasionally when letting off the throttle when in OD and only when little to no torque on the driveshaft. never does it in the lower gears. U-joint going bad? Thanks.

Franz

Since my last post I replaced the Crank Position sensor - no change. Checked Inertia Fuel Pump shutoff switch in Pax side kick panel - no indication it tripped, so no change. Checked fuel pressure at fuel rail Schrader valve - no pressure.

It would seem to be a fuel pump but I have heard that electrical/sensor failure can result in fuel pump not running as a safety precaution.

To recap: new head gasket (needed), new intake manifold gaskets upper and lower (needed), replaced front cover gasket (needed), replaced #2 piston connecting rod (bent from prior owner suffering head gasket failure), installed new TPS (no change), new Crank sensor (no change), new DPFE sensor (no change)..... any ideas??

pjohnson2882

I don't have the 4.2, I have the 4.9... Would the gasket issue still be the likely source for this engine as well?? I noticed something the other day... I went and bought a fuel pressure tester... The readings I got are as follows... And I'm not a master mechanic but k ow my way around a motor more so then the average person, keep in mind though that I've never went to school for mechanics just self taught.. Anyways... Fuel pressure readings are: koeo (cold), 12 psi front tank. Koer, cold 34 psi, front tank... Koeo cold back tank, 8psi. Koer, cold, back tank, 18 psi... Now- after I let truck run for ten minutes... Front tank... Koeo 32 psi, koer..40 psi... Back tank was substantially lower but forget the readings at the minute.... Could this mean that both pumps are failing and causing the codes?? Replaced fuel filter
already...

Edit; I've read that bad fuel pumps can cause these codes and from the beginning I thought that it may be the cause but because of the cost... Figured I would try the less expensive options first in hopes that's what's causing the codes... Because of the fuel pressure readings... I think almost for sure, that's what's causing the codes... But input would be much appreciated..

Marc D

I've been following this thread for several months now and and contacted a master mechanic I've known for years about the check engine light. Nobody wants to change the intake manifold gaskets because it's a lot of work, BUT it seems to be the majority opinion this is the solution to this problem. There are a 100 other reasons to throw 0171 & 0174 codes but barring the obvious bad vac hose EVERYTHING else is a suspect because of the electronics controlling the computer. I'm going to do the gaskets just because there's always a chance the water jacket seal could fail as well and trash the motor by hydrolocking it. P.S. the Ford dealer cost for the gaskets were 20% lower than NAPA, Auto Zone and RockAuto

Marc D

Well I sucked it up and changed the intake and plenum gaskets on my 2000 F-150 4.2 V6. In the process of removing the intake plenum (one piece aluminum on 98 to 2000) I found a factory vacuum 90 with a 1/8" hole in it. It would never be seen without using a mirror and knowing it was there. I went ahead and changed all the hoses, injector seals while doing the project. It took 2 days working slow and cleaning everything along the way. With all the parts and shop supplies it was $200 total. The truck started w/o any issues and at this point NO "check engine light"

shortyscwater17

i too have the 2000 4.2. can you tell me or take a picture of where the pcv location is. i see two spots where it could be but not entirely sure. thanks.

Marc D

I never got a great picture of the PCV valve but it's located at the very back of the passengers side valve cover. If it has a heater loop around it there will be 3 hoses connected to it. The 3/8 hose will have a Y and go straight up to the manifold and the other toward the front of the motor and end up under the plenum by the EGR valve. The other 2 hoses are 1/4" (inside diameter) and run to the water jacket on the intake manifold. Depending on how clean or dirty your motor is changing this can be a real pain. The spring clamps won't open, the hoses get stuck on the old PCV valve and you're on your belly straining to even reach the sucker. in the end I went to Ford, bought the correct valve, the factory pre-bent hoses and just cut the old hoses off. The parts cost was about $100. Note most of this cost was one hose assembly that went from the PCV valve to the front of the plenum ($67) I'll try to get a good pic for you today.

Billk2002

Great detailed write up photographically explaining the problem and the fix.