Error codes P0171 and P0174

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Apr 5, 2011 | 10:40 AM

HotRod32

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Joined: Mar 2008

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From: West Coast of Norway

Error codes P0171 and P0174

Hi.

I'm the lucky owner of a 1998 Expedition with 5,4L engine living in Norway.

For the past two years or so I have had the P0171 and P0174 error codes on my truck. I've tried most of the tips You have posted here on the forum, but without any luck. The Ford shop where I live have looked into the problem, also with no luck.

I've checked for vacuum leaks, changed all intake gaskets, EGR valve, and the small rubber knee in the back of the manifold, which by the way was leaking, the error codes still there.

Changed the gaskets along with EGR-valve/pipe last week, together with spark plugs (120 000 miles on car) and put all together again.

Engine still leaking (whistling when max engine vacuum). The power in the engine is poor, really bad ignition bank when acceleratin (valves/lifters/register-noise).

Anyone have other ideas i can try?

Regards,
Ole Ostigaard,
Ford enthusiast from Norway.

1932 Ford Hotrod
1955 T-Bird
1998 Expedition Eddie Bauer
2001 Explorer Eddie Bauer

Apr 5, 2011 | 12:16 PM

pdqford

Logistics Pro

Joined: Jan 2001

Posts: 3,740

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From: Central NYS

Quote:

Originally Posted by HotRod32

Engine still leaking (whistling when max engine vacuum).

Anyone have other ideas i can try?

What/where is the source of the whistle?

FInd someone with a smoke machine - insert smoke into the brake booster line and see where it comes out.

Apr 5, 2011 | 05:06 PM

2trux

Mountain Pass

Joined: Oct 2010

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From: Albuquerque

After 3 years of chasing the same problem on my '97 it was the MAF that fixed it.

Apr 5, 2011 | 07:38 PM

alloro

Fleet Owner

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From: 0,0,1

Quote:

Originally Posted by HotRod32

I've checked for vacuum leaks

Does your mechanic have a smoke machine? It pumps smoke into the intake and the smoke will exit wherever there is a leak. It's very useful for finding obscure vacuum leaks.

Apr 6, 2011 | 05:50 PM

hodges710

Senior User

Joined: Jan 2008

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From: New Hampshire

I had the same run lean codes on my 87 expy and it was fixed by replacing the o2 sensor. In my case, the one right before the main cat was bad. I thought maybe it would be more being both banks were running lean but everything came back to normal with just the one changed.

Apr 9, 2011 | 09:47 AM

HotRod32

Thread Starter

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Joined: Mar 2008

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From: West Coast of Norway

Smoke Test

Hi again, thanks for all the tips.

Tried with smoke in the intake. I have a second job working for a company that rents stage, sound and light for concerts etc, where we have lots of smoke machines. Used almost a can of oil, didn't see any smoke either from manifolds or from hoses/pipes.

Going for the sensors. Bought a MAF-sensor (OEM) from Summit racing, already have the O2 sensors in my garage. Will replace one at the time, trying to figure out where the problem is.

The engine almost stops when I'm pushing the pedal, but after a split second it runs okay. Happens on stop signs, traffic lights etc.

Regards,
Ole ostigaard.

Apr 9, 2011 | 11:34 AM

alloro

Fleet Owner

Joined: Apr 2008

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From: 0,0,1

Quote:

Originally Posted by HotRod32

The engine almost stops when I'm pushing the pedal, but after a split second it runs okay. Happens on stop signs, traffic lights etc.

If by pedal you mean the brake pedal and not the gas pedal, then your whole problem is a ruptured diaphragm in the brake booster. The leak appears during braking which throws the engine air/fuel mixture off. This would also explain why the smoke machine didn't show a leak.