[sdbuckeye]

I have to smog a 2008 Beetle, and the emissions light is on. The error code is P0171, system too lean.

I took the car to our standard (honest and reliable) repair place, and they have replaced the MAF three times now, first with an after-market MAF, then with MAFs from VW. Each time, the error code goes off, then comes back on within 24 hours.

We are late getting the smog done, help! What else could be wrong that the mechanics are missing?

 

[Smileybug]

http://wiki.ross-tech.com/wiki/index.php/16555/P0171/000369

I'd check for vacuum leaks. Sounds like your mechanic is just throwing parts at the car without really troubleshooting.

Sent from my SCH-I545 using Tapatalk

 

[jfoj]

MAF's are RARELY the cause of Lean codes/P0171.

Stay away from the shop you are using, these guys are IDIOTS!!! The mechanic you are using should be selling parts at the local parts store, not under the hood and working on cars. Sorry, but this is true, even if he is a "Certified" mechanic.

The VERY sad part is now the original MAF, that was probably good, is now gone unless they gave it to you and you kept it. The problem may now be compounded by a Asian counterfeit MAF that does not work properly??

Here is what you need, if you do not have an OBDII scan tool, you NEED your own.

You need to get and post the Freeze Frame data back for review and comment. Chances are there is a vacuum leak as mentioned, however, there are many other things that can cause Lean codes.

If you have an Android or iProduct phone or tablet, for under $30 you can get a GOOD OBDII App and interface that will do everything you need and far more. OBDFusion App is what you want. The VeePeak interfaces on Amazon are decent interface that work well. Android requires Bluetooth interface, iProducts requires Wifi interface.

But without data and/or a smoke test you are going to get nowhere.

Smoke tester for around $15 - https://www.youtube.com/watch?v=AsgB9eBl58I

 

[VDubYah]

p0171 system lean can be caused by the following:

Vacuum leak after MAF sensor
Bad or dirty MAF sensor
restricted fuel filter (low fuel flow)
fuel pump low pressure
exhaust leak before pre cat o2 sensor.
or rarely a bad o2 sensor

Short term fuel trims and long term fuel trim will help figure out what is going on. Post the freeze frame data and we will help you work through it without throwing parts at it.

 

[sdbuckeye]

Thank you for all of the help. I know very little about cars, but I can talk with the repair shop and ask about the diagnostic process they are going through with the car. I'll bring a list of the suggestions with me and make sure they're checking everything.

 

[jfoj]

Have the repair shop post all the requested information here and we will be more than happy to teach them how to diagnose and fix cars.

Sorry, but I get SO frustrated with these stories that I hear and read OVER and OVER again where no diagnosis is ever performed, parts are just changed then you get the blank stare when the problem is not fixed.

Not sure I would return or let the shop work on the car unless they could reinstall the original MAF and refund the money for that repair.