I have a 2003 F150 4.6 with 47,000 miles. The engine light came on and code 172 rich bank 1 comes up The dealer has checked everthing and cant find a cause. Any ideas?

 

Sounds like a vacuum leak.
1.)Search this site you'll find alot of info about vacuum leaks and how/were to look for them.
2.)Take it to another shop.

 

Vacuum leak for P0172?

I'd expect that for too much unmetered air ala P0171/174...you know, the opposite problem.

You're not getting enough air somewhere or there is a leaking injector.

How's the air filter looking?

Start pulling plugs on that passenger side bank and start looking for signs.

 

Yea - sticky injector I bet - if they couldn't find the problem.

I would check fuel pressure regulator. There is a spring valve inside. If the fuel pressure is higher than a preset value, it should force the valve open, sending excess fuel back to the fuel tank through the small hole in the tip (below the small O-ring). That's how the regulator manages to keep the pressure in the fuel rail constant. If the spring fails to open the valve , you could be over pressurizing the rail.

I bet they checked that at the dealership - they should have - Do you have ANY info of what's been tested/done?

Vacuum line (red) . Check the red line in vacuum harness. You'll see it when/ if you check the reg.

BTW - Take it to another shop , I agree 100% with that suggestion. Where- ever you took it before didn't want to bother with you for some reason - A professional shop can find that problem if they spend a little time looking for it.

 

Did the dealer give you a list of what they checked? The list of probable causes is blocked intake, EVAP purge valve, fuel pressure, EGR system, injector, and O2 sensor.

 

I have pages and pages of info. I dont understand it much.I can fax all of it to anyone. The truck has been at 2 Ford Dealers and 1 independent shop. Same answer The runs fine and the fuel mileage hasnt changed. Ive driven it 5000 miles with the light on.

 

If it runs fine and you haven't noticed a fuel mileage change then the problem is on the emission side. Did they check the EVAP purge canister?

 

P0172 - System to Rich (Bank 1) :

Air Measurement System

1. MAF sensor (contaminated, damaged, corroded connector, etc.).

2. Fuel System

Fuel pressure regulator (vacuum hose off, diaphram leak, malfunctioning, etc.).

Leaking fuel injectors.

Fuel return line restricted.

Fuel rail pressure sensor (incorrect reading).

EVAP canister purge valve leak (when canister is full).

 

I cleared the codes and drove it 250 miles today before the light came back on. 17.2 MPG and ran as good as it did new

 

The fuel table has been shifted to the lean end in trying to account of to much fuel in the exhaust as detected by the one Ox sensor.
Look for a leaky fuel injector, fuel pressure to high, leaking regulator diaphram, vapor cans system fault etc..
I suspect somebody at the dealership is either lazy or incompetent that they won't follow down the list of possibles. It's total baloney to say they can't see the problem.
I have the same list they do..
A good tech would put his scanner on and look at the fuel trim for that bank, then make some changes to see what will make it go lean (less fuel); maybe pull one injector plug off at a time to try to detect a leaking injector or at least to see if one make less difference if it is leaking steady etc.
If there is no common sense or effort to pinpoint the problem then it will be a long time before luck comes your way.
Good luck. Maybe try another dealer.

 

OOPS, just noticed my mistake. Though it was a p0171.

 

No problem. Codes 171-172 have the same cause list of faults.

 

its now been to 5 ford dealers and 9 repair shops and $2000 later. Still has code 172. Everythings been checked and rechecked or replaced. Have given up. I think a GMC or a Dodge would look good in the driveway

 

Above in bold - Personally , I doubt I wouldn't even check the components , just replace them . Both could be so intermittent, you'll never catch it until the component fails permanently.which means who knows when it's gong to fall out of margins .

A set of injectors on ebay - a new set =60 -80 bucks
Regulator isn't much at all, prolly $20 or so .

 

It's a shame this goes on like this.
Like I said some time ago, a good tech if allowed to really track it down, could find the problem.
It is a code for ONE bank only.
A tech with a scanner that knows how to use it can monitor several areas and see what is or is not happening and go after the issue without guessing.
You and others are at the mercy of dealer service that chosses not to persue these issues in a technical manner and so who gets the $2000 for all this?
This is why you need to look into the code, it's causes and use common scense to see when a dealer is not doing their job and shake the bushes a bit until you get results.
A scanner and all info to diagnos a problem are in force to use as long as some one will take the time to do it.
You came here for support, I give you the REAL skinny, now run with it.
Again, One bank only.
1. fuel injector.
2. air leak on one port.
3. Ox sensor.
4. It's heater wiring.
5. connector.
6. air leak in the exhaust ahead of the OX sensor.
7. more than one issue at the same time.
No use changing any parts that would affect both banks
BTW, a different make vehichle can have the same kinds of problems if present. So changing makes is not the real answer. Fixing it is.
Sorry to be a bit hard about it but reality has to be entered at some point.
Good luck.