Hello

Got the P0171 CEL and no other codes. No major symptoms or problems noticed while driving other then an occasional rough idle (RPMs bouncing rapidly between 800-1300 RPM approximately).

I would like to try and take care of this myself to (1) save money and (2) learn a little from it. I'm short on time though as I need to get new tabs ASAP. From what I've read, I don't think any of the common fixes are too time consuming.

Based on what I've read it seems the leading causes are VAC Leak, MAF, O2 Sensor, Fuel Filter. I replaced the downstream 02 sensor months ago with no change.

Any recommended DIY articles with pictures for replacing/cleaning the MAF sensor? I didn't see one at http://audidiy.com. Something like the following would be great I think - http://www.passatworld.com/forums/sh....php?p=2478676

I bought some MAF cleaner today so would like to try cleaning then replacing if I can.

I would also like to replace the fuel filter as that is something that should probably be done anyways. I think I'm covered with this article linked from audidiy.com

Finally, any tips or suggested resources/readings online on how to best check for vacuum leaks and replacing if necessary?

I will keep reading/searching some myself but though I would solicit feedback in the meantime.


http://www.go-audi.com/2346-audi-a4-1-8t-maf.html

• Rough Running At Idle - MAF, Ignition Coil, Spark Plug, VAC Leak, O2 Sensor, TB, CTS
• Running Lean – VAC Leak, MAF, O2 Sensor, Fuel Filter

 

In summary, I'm looking for recommended DIY articles with pictures for

1. replacing/cleaning the MAF sensor?
2. how to best check for vacuum leaks and replacing if necessary?
3. replacing fuel filter (if what I had linked is not good)

Anything else I'm not thinking of?

 

It's probably your MAF, you can unplug it, see if you still only have the same code, and see if it runs the same.....You have a 2001 so you have another sensor, and sorry, I'm drinking some beer so don't remember what it's called, but since yours is a 2001, it should have that other sensor which will let your car run even if your MAF is unplugged....

 

hahahaha, just remembered, later B5s, have what's called a MAP sensor, so if you unplug your MAF, your car will still run....

 

https://www.audiforums.com/forum/sho...d.php?t=154078 This is for your boost leak tester. You clean you MAF by spraying the cleaner on it and letting it dry....To replace bad vacuum lines, you remove the bad one by pulling it off (removing the retaining clip if there is one) and installing the new line.....The fuel filter link is fine.

 

Yeah start with vac test, before replacing parts cheaper to do!

 

That's a good word to the wise...start with the inexpensive solutions. These cars can be very moody and something small can be your problem.

 

Thanks guys.

The vacuum lines seem self explanatory. I guess my problem is just that I don't know what/where all the vacuum lines are but did do a check of what I thought may be relevant and THINK it's all good.

I bought some MAF cleaner and gave that a shot last night.

I went ahead and bought the replacement MAF from O'Reilly's ($300! Will probably look for and order another cheaper one online) since they have it in stock but have not replaced it yet as I want to give the car a bit more drive time since spraying the old MAF with the cleaner.

Now I'm hoping I can get input on whether I should (a) leave as is and drive x amount of time/miles to see if the CEL clears on it's own or (b) clear the light with the OBDII reader to see if the CEL comes back.

If I go with "a" then I do not know how long I go (miles/days/weeks) before I assume the cleaning was no good and replace the MAF. If I go with "b" my understanding is I need to wait about a week before going back to take the emission test but at least the light coming back on at some point would be more definitive then the waiting for it to maybe go off.

Any input on "a" or "b"?

Any suggestions for alternative place to purchase MAF - looks like there are a TON of options?

 

If it's a bad MAF and the cleaning doesnt work it shouldnt take too long at all...
As far as doing a boost leak and the vac lines... do this...
https://www.audiforums.com/forum/sho...12#post1225912 that will pressurize the system with the car turned off so you can hear leaking air to tell you if u have something off or with a hole.

 

I have an ebay maf for about 20k now and its doin fine...