Any help to this problem appreciated. The 'check engine' light in my 98 F150 went on intermittently over the past year, but always went out again after 15 miles or so. About 4 weeks ago, it would go on and stay on longer than it would stay off.

To my problem. I live in the great state of NY. My lovely state has a way of taxing us and that is called annual inspections. I have spent about $1000 to pass a $21 inspection so that I can continue to drive my vehicle. Anyway, I took the car in, had the Ford dealership run a diagnostic and they told me the DPFE sensor (EGR valve sensor) was bad, and that the intake to the EGR valve was plugged up. So I changed out both the DPFE sensor and the EGR valve, and the check engine light stayed on. So instead of paying for some more meaningless diagnostics from the mechanic, I bought a OBD2 code reader from Advance Auto. Now, it reads P0171 and PO174, both of which are 'too lean' readings. I have checked the vacuum lines (all good) have just replaced the EGR Vacuum Solenoid, poured SeaFoam into the intake to clean everything out. I have cleaned the MAF with MAF cleaner (it looks clean as a whistle). I have no manifold leaks.

What am I missing? Technically I'm not supposed to drive my vehicle from tomorrow, but I have a 'get out of jail free card', at least for another couple of days since I have taken it in for inspection and it technically didn't fail (another long story).

Any help greatly appreciated before I resort to a 45 magnum and armor piercing bullets!

 

Have you replaced the PCV valve with a MOTORCRAFT only unit? Using any other brand will buy you issues. Otherwise, you have a vacuum leak somewhere in the system and the PCV is the first place/thing I'd replace regardless if it looks good or not....if you've never replaced it before with a factory unit.

 

How did you test for intake gasket leak?

 

Right, I agree. Sounds like your developing pin holes in the elbow, which get worse in time.

Start with the correct PCV valve as Labnerd suggests (that's important) Then check your line. - Specially the elbow back by the firewall, rear of the intake -

 

Did you ever remove the throttle body and clean it - especially the EGR ports in it?

 

Find a shop that will gerntee that what they are going to will fix it or they will cont. to do what it takes to fix it, since this sounds like it could take longer then what you have time for.

 

have you tested your 02 sensor?