engine code 171 and 174

bigred1984 · 10-08-2009, 04:30 PM

I have a 2000 windstar with a 3.8l v6. It has 152,000 miles on it. My check engine light came on about 4 weeks ago. And my van started to run a little rough about a week ago. I just had the code read. It came up as code(s) 171 and 174.
What causes these codes and how do I fix the problem?
Is this a common problem on the vans?
Would that cause my van to run a little rough and get poor gas mileage?

Thanks

Cuda_Jim · 10-08-2009, 05:01 PM

P0171 - System to Lean (Bank 1)
P0174 - System to Lean (Bank 2)
I would check for intake manifold vacuum leaks first. It's the most likely cause.

If you don't find a leak then you will need a few specialized tools to help with the following system tests. i.e. a good scanner capable of reading PID's, VOM, Fuel pressure tester...the list goes on.

Fuel system

Excessive fuel pressure.
Leaking/contaminated fuel injectors.
Leaking fuel pressure regulator.
Low fuel pressure or running out of fuel.
Vapor recovery system.

Induction system:

Air leaks after the MAF.
Vacuum Leaks.
PCV system.
Improperly seated engine oil dipstick.

EGR system:

Leaking gasket.
Stuck EGR valve.
Leaking diaphragm or EVR.

Base Engine:

Oil overfill.
Cam timing.
Cylinder compression.
Exhaust leaks before or near the HO2Ss

bigred1984 · 10-08-2009, 05:40 PM

How can I check my intake for leaks?

theoldwizard · 10-08-2009, 06:09 PM

Like cause of P0171 and P0174

Expensive and not for amateurs.

bigred1984 · 10-08-2009, 07:02 PM

I have heard that you could maybe find a vacume leak by spraying carb cleaner around the intake and vacume lines to help pin point a vacume leak. Is this true?

theoldwizard · 10-09-2009, 04:24 AM

Quote:

Originally Posted by bigred1984

I have heard that you could maybe find a vacume leak by spraying carb cleaner around the intake and vacume lines to help pin point a vacume leak. Is this true?

TRUE.

Did you read the link I posted ?

bigred1984 · 10-09-2009, 08:50 AM

Yes I did read the post that was posted.
I just called the shop that worked on my van when I first bought it, they replaced the upper intake gasket and cleaned the MAF sensor. Now my question is this, how do I know if I have to do the proccedure done in that post? Or if its a lose line or something like that?

phantom_smack · 10-09-2009, 09:14 AM

If the shop did not change the isolator bolts it may still be leaking from the manifold.The intake set up makes it hard to find vacuum leaks with carb cleaner or even a smoke machine.

bigred1984 · 10-09-2009, 11:41 AM

So in other words I will probably just have to go ahead and do the procedure in the post? I had the codes cleared yesterday and the check engine light hasn't come back on. can this intake leak be the reason why I'm getting such poor gas mileage aside from needing spark plugs, wires, oil change, and maybe a fuel filter? Can an intake leak damage my van if I don't fix this asap?

phantom_smack · 10-09-2009, 01:50 PM

it will cause fuel mileage issues,I doubt it would get lean enough to do any damage.