well i have been chasing this problem for a couple weeks now. and the only codes left are
p01451, p0171 and p0174..the truck is still running rough at idle, stumbles on acceleration and has no power to keep highway speed...so everything that i have done has made things better but still not 100%
the p0171&4 are lean codes for bank one and two, the p1451 is evap system..this is what i have done so far...
new plugs
injectors
clean IAC
clean AIT
clean MAF
clean egr
two new O2 sensors
mil eliminators
cut out cats
pull the manifold vacuum harness off to make sure they weren't plugged
tried a new gas cap

the lean codes will also cause a misfire in 3,4 and 8 cyclinder on hard acceleration.

my next step is to try a new DPFE sensor and a evap charcoal canister..maybe change fuel filter..
anyone else had this problem before..if so please chime in and let me know what fixed your problem..thanks in advance....
fully

 

also i guess i should have metioned that my truck is a 98, 4.6l 4x4 270000km on it

 

Replace the PCV elbow behind the intake manifold.

 

PCV system leak and EVAP, but your running way lean without cats. They run like garbage with no cats,- your not tuned for it unless you hopped on the dyno. The 98 4six doesn't have much torque to begin with, that made it allot worse. Why did you remove all your cats? Did you need the money? You cash them in? 98 cats ARE worth quite a bit.

 

As stated MULTIPLE times before on this site. Use the search function and type in P0171 - P0174 codes. This is one of the most discussed problems on this forum. I have replied on this subject at least 3 times this week. Pretty much, anything you need to check for and repair you will find in your search.
I have found the #1 issue with these codes is vacuum leak in the PCV system but alot of others have run into, intake leaks as well. If you check your 90 degree elbow in the back (not sure what your's connects to on the 4.6 but on my 5.4L, it connected to my throttle body), you will probably find it is worn out if it is the original part. I thought mine was fine but still had the codes come back. I said the heck with it and replaced the entire PCV system from Ford and have been code free ever since.

 

He posted misfiring at one time.

My guess is that it's running so fricken lean the plugs are over heating.

He's gottuh thro at least one cat on there before it's to late, that's very bad.

 

Running with no cats is no good, and even if you aren't subject to inspection it's illegal and no good for the environment. Throw a pair of high flows on it.

 

Or atleast the forwards -



Even if your just running the forwards , your still within parameters. You can run all 4 O2's as well and get rid of those eliminators, you won't get a CEL.

You can get away with this -



But you have to have something running the stock tune.

__________________________________________________ ___

High Flows are definitely best of course, like this -

 

well for one, i was miss firing, and running lean before the cats were cut out. they were plugged, today i put a different dpfe sensor on and got rid of the lean codes so far, the only code left is the p1451 evap, put a different canister in and no change

 

Well for one, I hate to tell you this,- the DPFE has nothing to do with your lean codes, -make up what you want, but you won't fool to many here. You have a leak,- period (glc pointed out what to check)..And running without cats is not helping, it's compounding, - period.

You asked for help and got it, but why ask if you know better, - right?

It's your truck , your problems - Good Luck with all that.

 

i wasn't trying to be smart with you i was just posting in reply to this. that this was happening long before i cut the cats out......

 

http://www.aa1car.com/library/ford_lean_codes.htm

and according to this article yes the dpfe sensor can affect the lean codes read it and see..it near the bottom of the article...

 

http://www.aa1car.com/library/ford_lean_codes.htm

BAD DPFE SENSOR

Ford p0171 AND p0174 lean codes can also be set by a bad EGR differential pressure sensor. These sensors have a very high failure rate once a vehicle has more than about 60,000 miles on the odometer or is more than five or six years old.

The DPFE sensor is mounted on the engine, and is attached with two rubber hoses to the tube that routes exhaust gas to the EGR valve. The original equipment sensor has an rectangular aluminum housing about three inches long. Corrosion inside the sensor reduces its sensitivity to EGR flow, causing it to under-report EGR flow. The PCM responds by increasing EGR flow, which may keep the EGR valve open longer than usual creating a lean condition in the engine. Thus, a bad sensor may set a P0401 code (insufficient EGR flow), or it may not set an EGR code but a P0171 and/or P0174 lean code instead.

The cause of the P0401 code in most cases turns out to be a bad DPFE sensor, not an EGR valve problem or an EGR valve that is plugged up with carbon (though this can also set a P0401 code). An aftermarket replacement DPFE sensor costs less than $50 and usually gets rid of not only the P0401 code, but also the P0171 and P0174 codes, too.

Your right, it's possible. Just not likley. Your running so lean to begin with (without cats/ on a factory tune), it might have, it sure wouldn't take much to push it outside of parameters. It's your truck, just keep running it that way and you'll be back with a different problem lol. It has to be running like crap right now.

 

i was running lean before the cats were cut out. and so far the dpfe sensor change has got rid of the lean code...the only code i have left is the p1451

 

I've never heard of that, but there has been cases where we couldn't figure out where or why lean codes where present. Thanks for the link and please report back if these codes return