2000 F350 V10 P0171 and P0174 ?
I am having an issue with finding the cause of this problem, hoping someone can give me a logical method of eliminating possible causes.

THE STORY: Truck was down for leaf spring replacement for about two weeks. Upon starting the motor bobbled a bit before smoothing out , figured it was from sitting. On my way home from work ,I could not get above 1500 rpm. 45 mph on the shoulder for about 25 miles. Check engine light came on. Reader shows P0171 and P0174, lean in bank 1&2.

THE PROBLEM: Truck will start and idle around 800 rpm. As soon as throttle is applied , the motor flat lines and eventually will stall. I sprayed cab cleaner everywhere looking for vacuum leaks. Found none. Did replace the vac hose under the throttle body because it felt spongey. Had a buddy help me out, he unplugged the MAF sensor. The truck responded almost normally(rpms came up when throttle applied) . So I replaced the MAF sensor for $200. Plugged it in, SAME PROBLEM.

THE QUESTION: ANY IDEAS?

 

First, get the codes read. Then get a gauge and check your fuel pressure.

 

May be your air/fuel ratio has been affected by an air leak somewhere in the system in order to trigger those error codes . Some suggestions;

1-Be sure to check the rubber elbows on all the plastic vacuum lines - Especially the 90-degree PCV hose end @ throttle body.


2-Check to make sure the MAF sensor's rubber-grommet on the bottom of the air-filter housing is in place. It seals the MAF wiring to the filter housing. I've seen them pulled out when people have changed the air- filter. If it's not sealed you have air by-passing the MAF and that can lead to the codes you have.

Good luck,

 

I do have access to a good snap on scanner. Unfortunately not until Monday night. I will check fuel pressure. I just replaced the elbow under the throttle body( about ten minutes ago).I did replace the fuel pump last year. Checked the grommet on the MAF. All good. I will detail the smaller vac lines tonight. Thanks for the help. This is really A cramp. But staying positive, every problem has a solution.

 

Second that. I had mine down for 3 weeks, headers and exhaust. When I started it back up it ran just you describe and threw the same codes the next day. Was the rubber grommet on the bottom of the air housing. It's hard to see, have to feel down there and see if it's loose. But common sense tells me that's most likely not your issue since you replaced your MAF and you had that off so surely you have double checked that already, but if not, replacing the MAF if you don't have that grommet tight - still going to have the same symptoms. If not your codes are running lean so it's either an air issue throwing off your mixture or a fuel issue.

 

i had the same problem also and mine WAS the Mass airflow sensor, i would try returning the one you got and get another one...it is possible the new one is bad also...guy at the parts store told me they get alot of defective ones

 

Ok , here's where I'm at: Fuel pressure good, MAF installed correctly, built a smoker to test all vacuum lines and system($35 I'll post a pic after I get back on the road). Did have smoke coming out of the small black cap on, what I believe to be the AIC. Probably had about 5psi in the vac system at that point.
AGAIN THE PROBLEM IS NO ACCELERATION, BUT ONCE THE MAF IS UNPLUGGED ALL SEEMS GOOD.

I will try to return the MAF sensor tomorrow for a different one. Will let you know what happens. Thanks

 

P0171 and P0174 mean you have air leaking into your engine downstream from the MAF.

Your smoke test told you the IAC is the problem, why are you ignoring that?

 

Redford, I did pressurize the vac system and I'm not sure what the small port on the AIC is there for. If you can shed some light on it it would be appreciated. Thought it might be a blow back valve of some sort.Have you had any issues with the AIC causing this issue off idle? I don't want to over look anything.

 

I think you mean the IAC, which is the Idle Air Control valve. It is supposed to regulate air going into the intake manifold at idle. If it stays open, it will cause your symptoms.

 

Makes sense. I'll look at it a little closer. And oh yea, I was 67 uniform a lifetime ago. Medium helicopter repair, U.S. Army. Thanks again.

 

I started my career in the Army. 36L20 (telephone switching), 36C20 (cable splicer), 72E10 (switchboard operator), and 55D20 (explosive ordnance disposal). Got out, then joined the Air Guard. Ended up a 2E691 SEI-200 (Wire Superintendent, Special Skill Identifier Engineering Installations Team Cheif) when I retired.

 

Replaced the IAC last night. No change. Problem still exists. Starting to think there is a problem with the wiring or the computer. Having a buddy stop over tonight that is more familiar with the high end scanner/reader I'm borrowing for the weekend. If I don't figure it out over the weekend, it's going to ( I can barely write it) the dealer. UGH

 

A dealer is a viable option for diagnostics - but if it were me I would set clear instructions that you are paying them to diagnose the problem and they are not to touch anything above what it takes to make that diagnosis.

Have them give you an estimate to repair whatever they find, then take that estimate and either get back on here and get help to do the repair yourself or shop around and find a good local mechanic with references.

 

Spent another 5 hours this weekend on the truck. Tried another MAF sensor, same problem. Decision has been made. Take it to the dealer for diagnostics. I believe it's a wiring issue or computer problem. I'll let you know what happens.
Thank you all for your input.