2001 4.2l rwd p0401 p0305 p0174
 

changed all spark plugs/wires last year, changed coil pack, brand new EGR valve, changed DPFE sensor last two years(thank god for warranties), about to try changing it again. anything else i might try? my inspection is out so any help is very appreciated.

changed the DPFE today and put in some injector cleaner, drove it about 20 miles and the codes haven't come back. im gonna take it up to get inspected tomorrow and pray it passes.

Right before you take it in, disconnect the battery. Should clear any codes for about 60 miles. I've done that to pass before since I didn't have time to get the issue resolved until about a month later.

Did the ijector cleaner work? Code come back?

Mine 02 4.2l has always thrown those codes I replaced 02 sensors and all. The CEL came back on took it to ford and the told me it's the upper intake manifold gasket that causes that. It has something to do with the bolts and the loosened up and the gasket and bolts need replaced. I haven't dine it yet just put black tape over CEL LMAO. I don't have the tools to do it myself and dont have the money to have I done. Ad it docent seem to be hurting anything. So I will wait on it. LMAO. That is what my prob with the codes are hope this helps.

Code PO174 (left bank lean) and PO 305 (cyl 5 misfire detected) both point toward the common intake gasket issue. Don't see the relation to the PO 401 (insufficient EGR flow). If you do decide to tackle the intake job, buy the Ford parts, a material change was made and a TSB issued. Doubt very much if aftermarket even cares about improving their parts line.

I was just one of the unlucky ones who's intake gaskets didn't go bad, the lower intake manifold completely cracked with under 100K miles on the truck. I was having a P0171 and P0174 codes that were caused buy the MAF...eventually it got to the point where the computer was saying 3 out of 4 of my O2 sensors were fried as well before I got the MAF replaced by a mechanic who knows 4.2's better than anyone at a Ford dealership.