Go Back   AudiWorld Forums > Audi Models > Audi A6 / S6 / RS 6 > A6 / S6 (C5 Platform) Discussion
Sign in using an external account
Register Forgot Password?


A6 / S6 (C5 Platform) Discussion Discussion forum for the C5 Audi A6 and S6 produced from 1998-2004

Welcome to AudiWorld Forums!
Welcome to AudiWorld.com.

You are currently viewing our forums as a guest, which gives you limited access to view most discussions and access our other features. By joining our community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join the AudiWorld Forums community today!


Reply
 
 
 
 
LinkBack Thread Tools Search this Thread Display Modes
Old 10-04-2013, 03:20 PM   #1
Audiworld Junior Member
Account #: 267092
 
Join Date: Sep 2013
Posts: 17
Default Mass Air Flow (MAF) question for replacing

So I replaced my MAF on my 2002 Audi A6 2.7t. And it did not fix the problem of hesitation and jerking and bouncing within a range of RPMs.

When I had it unplugged it worked fine. Is there anything special I must do when replacing with a new MAF? I did disconnect both battery terminals is there anything I must do when putting a new MAF on my car?

Keep in mind the old MAF was doing the same thing. If I unplug the MAF it works a lot better and smoother almost normal.

Thanks
atg614 is offline   Reply With Quote
Old 10-04-2013, 03:47 PM   #2
AudiWorld Member
Account #: 162750
 
nm3210's Avatar
 
Join Date: May 2009
Posts: 194
Default

Definitely check for vacuum leaks and I don't think you can completely rule out that the new one was good (I'm assuming it was used?). Or who knows maybe the connector/cable is bad? Make sure to clean all the contacts and look for bare wires.
__________________

1999 A6 Quattro 2.8L, with 190k miles, and a 130k engine (timing belt tensioner, bleh)
http://www.vaglinks.com/VAGLinks.asp
http://sonolithics.com/files/a6_links.html
nm3210 is offline   Reply With Quote
Old 10-04-2013, 05:59 PM   #3
Tech Guru
Account #: 43812
 
4Driver4's Avatar
 
Join Date: Oct 2002
Posts: 33,256
Default

Boost leak.
__________________
4Driver4

Growing old is mandatory; growing up is optional.

2005 A6 Sedan Q 3.2 (wife's whip)
2000 A4 Avant Q 2.8 (daily driver)
1980 VW Scirocco (mid-life crisis car)
1983 Mazda RX-7 (revolutionary sports car)
2003 Mini Cooper S (just because)
1995 Mazda Miata, Superdupercharged(anti-Audi)
1999 Mazda Miata SSB (track beotch, no plate)
2003 GMC Yukon Denali XL (the anti-earth)
2004 Dodge Dakota (hey, at least it's stick and 4x4)
4Driver4 is offline   Reply With Quote
Old 10-05-2013, 04:35 AM   #4
Audiworld Junior Member
Account #: 267092
 
Join Date: Sep 2013
Posts: 17
Default

Quote:
Originally Posted by 4Driver4 View Post
Boost leak.
Do you mean a leak by the turbo boost?
atg614 is offline   Reply With Quote
Old 10-05-2013, 09:41 AM   #5
AudiWorld Senior Member
Account #: 220156
 
Join Date: Aug 2011
Posts: 1,611
Default

You have a large intake leak after the MAF, so any of the intake plumbing, intercoolers, crankcase ventilation system, or intake manifold leaks will cause big problems. Disconnecting the MAF makes the engine run on preset values and leads me to believe its something between the MAF and throttle plate and not a manifold vacuum leak.
__________________
1991 Audi 200 Turbo
1999 Audi A6 Avant 2.8
1998 Audi A4 quattro 1.8T
Prospeeder is offline   Reply With Quote
Old 10-05-2013, 04:05 PM   #6
Audiworld Junior Member
Account #: 267092
 
Join Date: Sep 2013
Posts: 17
Default

Quote:
Originally Posted by Prospeeder View Post
You have a large intake leak after the MAF, so any of the intake plumbing, intercoolers, crankcase ventilation system, or intake manifold leaks will cause big problems. Disconnecting the MAF makes the engine run on preset values and leads me to believe its something between the MAF and throttle plate and not a manifold vacuum leak.
Ok, got some of that. I disconnected it again and runs 10 times better.

Possible places I could check for leaks? I do not have pressure test system. Could I use smoke from a cigar? Any suggestions?

Trying to get my hands around what you said. So with preset values even with leaks how does that happen to still run smoother with MAF disconnected? Should I try cleaning the new MAF I received? Or return it for another new one from where I got it? The error codes I am getting are P0103 and P0175. MAF error and system 2 rich bank 2.

Now my car has 155k miles, should I be concerned about the Diverter valves and N75 valve? Change those at this mileage? are they known to go?

Thanks for the help.
atg614 is offline   Reply With Quote
Old 10-05-2013, 06:48 PM   #7
AudiWorld Senior Member
Account #: 220156
 
Join Date: Aug 2011
Posts: 1,611
Default

So the MAF reads air coming through the intake to the engine. If the engine pulls air through a different location, like a boost hose blew off under the car, then there will be no/lower MAF signal, no MAF signal, you get codes and poor running. You unplug it, then its running on preset values, not being fooled by the lack of MAF signal.

Actual engine vacuum leaks really affect mixture directly, so even on preset values it may run too lean and run poorly. Doesnt mean thats its impossible though
__________________
1991 Audi 200 Turbo
1999 Audi A6 Avant 2.8
1998 Audi A4 quattro 1.8T

Last edited by Prospeeder; 10-05-2013 at 06:50 PM.
Prospeeder is offline   Reply With Quote
Old 10-05-2013, 06:59 PM   #8
Audiworld Junior Member
Account #: 267092
 
Join Date: Sep 2013
Posts: 17
Default

Quote:
Originally Posted by Prospeeder View Post
So the MAF reads air coming through the intake to the engine. If the engine pulls air through a different location, like a boost hose blew off under the car, then there will be no/lower MAF signal, no MAF signal, you get codes and poor running. You unplug it, then its running on preset values, not being fooled by the lack of MAF signal.

Actual engine vacuum leaks really affect mixture directly, so even on preset values it may run too lean and run poorly. Doesnt mean thats its impossible though
Ok that makes sense.

Being I don't own a pressure test system. What "DIY" could I use to help determine where leak is? Also do you think at a 155k the Diverter Valves and N75 should be replaced regardless? DO they last a long time?

Thanks for the help and understanding.
atg614 is offline   Reply With Quote
Old 10-05-2013, 07:52 PM   #9
AudiWorld Member
Account #: 237856
 
Join Date: Jun 2012
Posts: 339
Default

Quote:
Originally Posted by atg614 View Post
Ok that makes sense.

Being I don't own a pressure test system. What "DIY" could I use to help determine where leak is? Also do you think at a 155k the Diverter Valves and N75 should be replaced regardless? DO they last a long time?

Thanks for the help and understanding.
Agreed...check for leaks and codes with VCDS. Had the exact same symptom so I purchased a new hitachi maf (now I have two because I went to a larger MAF so I have the original MAF, and a brand new Hitachi). Found it was a simple boost leak. The intercooler hose blew completely free.

Search and you will find a cheap DIY on how to test for boost leaks. You used a 3" rubber plumbing coupling, a 3" pvc cap, and a compressed air hose fitting. Very easy and cheap.
slowguy is offline   Reply With Quote
Old 10-06-2013, 07:50 AM   #10
AudiWorld Senior Member
Account #: 220156
 
Join Date: Aug 2011
Posts: 1,611
Default

Just check all the boost hoses. There are ones from the turbos to the intercoolers that blow off and loosen up the clamps. Theres hoses from the top of the intercooler to the throttle body, theres the big Y intake on top of the engine with the DVs plumbed in. Dont just look, grab and try to pull on the rubber pipes.
__________________
1991 Audi 200 Turbo
1999 Audi A6 Avant 2.8
1998 Audi A4 quattro 1.8T
Prospeeder is offline   Reply With Quote
Old 10-06-2013, 07:50 AM
AudiWorld
Audi R8




Paid Advertisement
 
 
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -8. The time now is 01:31 AM.


Copyright 2014 AudiWorld.com Audi Enthusiast Community