Contour Enthusiasts Group Archives Forums General Troubleshooting Codes: 171 and 174

Hey guys how ya doing???

My check engine light has been comming on for sum time now probably for the past 2-3 months.. I keep getting it check and all it says is 174 and 171, the 171 code only came on once so far but the 174 comes on like once or twice a weak... So far I replaced the fuel filter and ran sum fuel injector cleaner through and seemed to help for a couple days but the light just came back on today... So any other Ideas what it could be???? I was thinking a bad O2 sensor but I dont wanna go spend $150.00 for 02 sensors till I am sure that is the problem is!!!! The weird thing is the car runs really, really strong, just the check engine light comes on and I share the same stalling problem I am seeing every one else talk about!!!

Thanks in advance..

Tommyboy

P0171 System Too Lean - Bank No. 1.

P0174 System Too Lean - Bank No. 2.

I have no idea after that...

P0171 System Too Lean - Bank No. 1.
P0174 System Too Lean - Bank No. 2.

It's not uncommon for upstream O2 sensors to report these faults intermittently when they start dying after 60K miles or so. If the car idles and runs smooth, then the O2 sensors are probably going bad. If you have other problems like a rough idle or missing you may have an intake leak inboard of the MAF. Spraying a shot of electronic parts cleaner (radio shack) on the MAF sensor element may also help. O2 sensors are about $60 each at some discount auto stores.

There is a lot of info already posted on replacing the sensors if you do a search on this.

The Mass Air Flow (MAF) sensor measures all air coming out of the air filter and into the engine. An intake leak that is inboard (i.e. closer to engine) of the MAF would be letting air into the engine that hasn't been measured by the MAF and could mess up the air/fuel mixture to both banks.

First confirm that your plugs and wires are good and that they aren't making the problem worse. Next check every hose and hose clamp on the intake side of your engine to look for any cracks or leaks. If everything is tight and not leaking, check the throttle body and upper intake manifold for leaks. The gaskets below the UIM could be bad, but please check for a lot of other causes before pulling the manifold(s) to look at these. It's best to replace these when reassembling.

Make sure all of the PCV hoses are hooked up, and that the PCV valve is not stuck open.

The MAF may be dirty, spray off the element.

Ya check your PCV valve. I had the 171 code come on for a few minutes only. A couple of weeks later I noticed oil all over the PCV valve area. Sure enough it was faulty. I haven't seen the code again.

I had these same codes come up and the same rough idle. Check all vacuum lines then check the upper intake manifold gaskets by squirting carb cleaner at the mating surfaces while running. I found mine were shot and 1 vacuum line was collapsed. $30 later and an hour of labor last night and she is running like a champ again.
96 Contour SE
2.5 V-6

  As has been suggested already, your MAF might be dirty.  Cleaning it is very cheap and easy, and has been known, in many cases, to clear up P0172/P0174 issues.  It might not solve your problem, but it's so easy,and so cheap, that it makes very good sense to try it before you even think of lookng for a more expensive cause.

  It's very easy.  If you don't know what your MAF is, just look at the large hose that runs from the air filter to the throttle body.  The MAF is the thing that connects the two sections of that hose.  It almost looks as if it's primary function is to connect the two shorter lengths of hose to make a longer hose.

  It's very easy to remove the MAF, and later, to reinstall it.

  One you have it out, here's what you do to clean it:

  Look into the side of the MAF that goes toward the air filter.  You'll see two small wire coils, close together.  That's your target.  Spray these liberally with standard aerosol carburetor cleaner; and then afterward, spray it liberally with non-residue brake cleaner.

  Reinstall the MAF (making sure you get the airflow direction right), reset your PCM, and give it a try.