Intermittent CEL, p0171, p0101 - is my MAF sensor bad?
 

I'm hoping for some help diagnosing my wife's 2001 Jetta (2.0 engine). In the middle of summer the CEL came on after a bit of exhaust work was completed. The garage scanned it, told me it was a bank one system too lean, said it didn't have anything to do with their work. They cleared the code and sent me on my way.

There were no drivability issues with the car, and I, being cheap, hesitated to have anyone qualified look at it. We drove the car on long vacation (4K miles), during which time the CEL was off some of the time but on most of the time. A couple of times it ran a bit rough during the first few seconds after restarting when the engine was warm, but there were no other noticable symptoms.

I replaced the engine temperature sensor because the gauge wasn't working. This fixed the gauge, but not the CEL. So finally I knuckled under and took it to the dealer.

The dealer's mechanic found codes for a faulty temp sensor, and also the original 'system too lean' code. He discovered and fixed a small vacuum leak, on which he blamed the lean code. He also speculated that the bad temp sensor code could've been from before the sensor had been replaced. He cleared both codes and sent me on my way.

Three days later, the CEL came back on. I suspected the temp sensor I'd gotten was defective, so today I stopped by a local (cheaper) garage to have the code read again. Instead of a code referring to the temp sensor, we got the two codes I mentioned in the thread title. P0101 refers to a non-specific MAF issue, while P0171 is the system too lean (again).

So, being cheap, I'm wondering if I need to take this into the dealer for an expensive, in-depth diagnosis, or would I do just as well to simply replace the MAF sensor and see what happens?

I'm thinking with my wallet-related anxiety, and I fear my judgement is clouded. Please help me see the sensible course of action.

Thanks.
Jon

RE: Intermittent CEL, p0171, p0101 - is my MAF sensor bad?
 

It could be, cause the air passing through your sensor lets the ECU determine fuel delivery. If you have a MAF sesnor problem it may think you're getting too mcuh air and lessening the fuel delivery

RE: Intermittent CEL, p0171, p0101 - is my MAF sensor bad?
 

Posting for posterity, in case anyone else has a similar problem. I took a chance and bought a new Bosch MAF sensor ($105 on ebay) and installed it. About 45 miles later the CEL went out and has stayed out for about 200 miles since then. It looks as if that does it.