i've got a 2003 E-150 van with a 4.2 with 83,000 miles on it with codes 171, 174, 1131, 1151. I changed the fuel filter, plugs, isolater bolts, lower intake set, upper intake port seals,and intake cover gasket. the dipstick is seated and I tightened the oil fill elbow. The pcv tube is ok, cleaned the MAF,EGR valve, and throttle body. Ran injector cleaner through it, the fuel pressure is within spec. I plugged all the vacuum lines one by one and no change in the fuel trims on my scanner. My Snap On solus does not give me freeze frame data for fords, but after the intake gaskets were done it ran a heck of a lot better cold, but can't keep the light out. Any ideas?

 

Monitor your short term fuel trims while spraying anything and everything with brake cleaner or similar. If any of the cleaner makes it into the engine's intake, you'll see a sharp change in the STFTs that will take a few seconds to return back to "normal".

Also, if the Solus will let you look at your MAF PIDs, those would be interesting to see if the MAF is supplying correct data.

Steve

 

I had a similar problem with my 94 Mustang GT. Kept getting "lean condition" codes on both banks, no sensor failures. Went through the whole electrical system with a voltmeter, came up empty. Finally found a TSB about possible MAF failures, changed it out, and wow what a difference, no more lean codes and the power returned.

 

Update: I found the freeze frame data in my Solus. p0171 set at 642rpm, 174ect, 0 vehicle speed, with roughly 32% stft correction. Sounds like it was idling in gear as it was warming up when the code set. I tried a new MAF with no change in the MAF PID, also has plenty of power. All the intake gaskets are new along with isolator bolts,and ran a lot better after I replaced the gaskets, just can't keep the Check Engine light off, for lean codes. I am thinking fuel system, any other suggestions?

 

how many miles on your O2 sensor? most are contaminated and damaged by 83K..probable antifreeze contamination from old IM leaks

check for low fuel rail pressure

 

I tried new o2s with no change. the fuel rail pressure is within spec at 38psi on prime and 30 psi at idle, 38 psi at WOT.