Taylor13

I thought I had finally corrected the rough idling problem on my 99 F150 when I replaced the elbow hose off the PCV. Just as everyone in the forum kept saying, I also had a hole at the elbow on hose coming off the PCV. After changing this, the truck is running smoother than ever, but the Service Engine Soon light keeps coming back. I reset the codes by disconnecting the negative terminal on the battery, and the light stayed off for 3 days, but the light is back. I have absolutely no engine performance issues that I can feel or hear. Any ideas.

Thanks!

djfllmn

iTrader: (1)

whats the code?

Taylor13

I haven't checked since it came back on yesterday after replacing the PCV elbow on Saturday. Prior to this, I was told the codes were related to lean bank 1 & 2 and the EGR. Most posts I've read have said the EGR seldom goes bad. Whatever the reason for the light, my little 4.2L is running as quiet and smooth as new. Perhaps I leave the light alone and go on down the road.

djfllmn

iTrader: (1)

get the code pulled again

Marc D

Although I'm a new member I followed several threads and done web searches on this issue. Bottom line there's a vacuum/ manifold leak that's creating a lean condition in the fuel. My 2000 F-150 w/ a 4.2 is throwing 2 codes P0171 and P0174. With out success I've cleaned the MAF, changed the PCV valve and replaced the EGR pressure sensor. Ford says pull the intake manifold and replace the bad bolt shims and gaskets that were a factory design flaw.I'll try a new EGR valve first but I think the manifold will have to come off.
By the way my truck runs great too but don't be fooled lefted unchecked this condition will eventually damage your cylinders and blow out you cats.

forayzor

Intake manifold gaskets are extremely common on the 4.2

Taylor13

Pulled the codes today - P0401

forayzor

I believe that's EGR insufficient flow? If so, could be your DPFE sensor, the old aluminum body style sensors failed constantly. Also could be EGR valve, or the hoses to the DPFE, or EGR ports under upper intake.

Marc D

I replaced the EGR pressure sensor ($75) even though I only had the P0171 & P0174 lean codes but the light returned shortly after clearing it (3 to 4 min. of driving) I did discover a long 3/8" hose to a sensor on the firewall from the intake manifold that looked fine. When I touched it, it crumbled on the surface like black dust. I can't tell if it's leaking but I'll change it today with some bulk hose, since a factory bent hose could cost $50 like the heater hoses I changed a few months ago when I replaced the heater core. It seems almost impossible to trace all the vacuum hoses around the manifold to check for leaks

pjohnson2882

HELP!!! Mil won't turn off!!! I have codes p0174 & p0171... I have a code reader and have cleared the codes after each thing replaced... So far I have changed, the fuel filter, maf, egr valve, Pcv valve, plugs, wires, cap, rotor, oil change, low temp thermostat, 02 sensors, air filter, cleaned throttle body, sprayed around vacuum lines with carb cleaner to listen for change in idle... Heard a very light change in idle but can't get it to do it again... And can't find any issues with lines... Any ideas!! Please help... Going nuts!!