Contour Enthusiasts Group Archives Forums General Troubleshooting P0171 & PO174 ( again)

Hey all,
I had a P0171 for several months and just before I was about to replace Bank 1 precat O2 sensor I found a P0174 as well. I've been searching the site and have put together a priority list for myself. My tour is due for a tune-up ( 108K) but I wanted to target the CEL codes first. Other than the CEL light, the car runs fine. I'm also not hearing a hiss indicating a vacuum leak so I don't really have anything to zero in on. So here's what I think:

1)retorque UIM bolts to upper end of spec. (8-12 N-m)
After retorquing use aersol carb. cleaner to check for failing gaskets/seals.

2)clean MAF with electrical parts cleaner. Don't use q-tip.

3)replace PCV valve, Ford part is best (IMHO) eventhough it's plastic. Replace large vacuum hose to intake (order from Ford?). Use O clamps around PCV hoses. Clamps will help insure air leaks aren't present.

4)inspect DPFE (dynamic pressure feedback EGR).

5)replace fuel filter and air filter.

6)replace spark plugs and wires.

7)replace bank 1 pre-cat O2 sensor.

8)rebuild UIM and LIM using How-to.

9)?

Thanks for any input.

yap31

Since you have a 96 I would move cleaning the intakes and replacing their gaskets to the front of the list. This will stop future intake leaks from occurring and get rid of EGR buildup too. It will be easier to do other work at that time, just be methodical.

Actually, you should do both banks pre-cat O2 sensors at the same time if you wanna be able to leave your hood shut for awhile. I did just one on mine at first, and the other one quit like 5000k mi later. And it happen when I was out of town on vacation, so if you want to be preventative then I recommend doing both of the primary sensors

So basically the UIM & LIM intake rebuild is necessary because of my car's age and mileage. Even if both CEL codes don't go away it will allow me rule out a known problem with Contours, right?

Regarding the O2 sensors, if I replace one and the corresponding code goes away I'll definitely replace the other one.

Thanks for your responses.

I do believe, your codes for the downstream 02 sensors could also signify a plugged precat. I would rule that out before buying the sensors. John.
P.S. Yapper, how do you go about checking for vacuum leaks? Thanks.

I'm only pulling two codes off the scanner. P0171, "Lean condition Bank 1" and P0174, "Lean condition Bank 2". I'm pretty sure the pre-cats aren't involved since P0171 and P0174 mainly use the forward O2 sensors. If the pre-cats were involved I'd think I'd get a code like P0420, Catalyst efficiency below threshold Bank 1. Anyone else agree my precats may be influencing these DTCs?

Ya yapper your right. Sorry my mistake. But tell me how to go about checking for vacuum leaks

to jmatzick:
I'm not really an expert but I believe short of hearing the leak(hissing) using aersol carb cleanear or starting fluid is the second best way to identify unmetered air getting to the engine. I had a Toyota with a leaking intake manifold gasket and I used carb cleaner to repeatedly smooth out a rough idle. I'm thinking I could spray around the base of the UIM/LIM and if the idle changed a loose or leaky gasket/seal would be suspect

to Rogerm60:
I'm going to order the part for the UIM & LIM intake rebuild. From your description doing this first will probably solve my problem. Regarding EGR build up, is it necessary to remove and clean or replace the EGR valve or other emission components once I have the intake system off the car. Any thoughts? I'm not looking for trouble but I only want to do this once. If it's not a big deal to do EGR stuff after I've done the intake rebuild I'll tackle it when the need arises.

Once again thanks for your reponses.

yapper

You will need to remove everything from the UIM to thoroughly clean it. There is a tube in the UIM casting from the EGR boss over to the throttle body. Run something through it to clear it out. Be sure to dig the carbon out behind the throttle body gasket area. Many posts on this.

Get the intake gaskets, throttle body gasket, EGR gasket, and IAC gasket. The EGR valve itself rarely causes a problem, and is easy to get to at any time. Clean only if lots of buildup, and by scraping with hardwood.

Be sure to read: Intake rebuild

This may not be the current problem, intake leaks usually cause driveability or cold weather problems. Better to do it before it strikes, and doing work on the engine may trigger the cracked and dry rotted seals to break anyway.