Maf
Thread Starter
Teching In
Joined: Sep 2005
Posts: 6
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Maf I just bought an A4 00 ws6. The car runs great. but i was just wondering if running the car with the Maf sensor disconnected will cause any problems to the car? Im asking because when i bought the car it was disconnected and the car ran real good. it would fishtail hitting second gear with the transmission in regular drive. when i connect it. its still peels out but the car doesn't feel as strong. can somebody help me out
It will run better with the MAF plugged in, if the MAF is working correctly. By unplugging it, the computer runs in a different parameter monitoring configuration, and your fuel economy is probably going to suffer quite a bit too.
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
also depends on what the previous owner tuned the car for... !MAF causes the PCM to go into a failover mode (Speed density in our case) ... the PCM uses the MAP, IAT, and O2 sensors to determine fueling requirements when in closed loop and just the IAT and MAP for open loop. (closed loop = normal driving, open loop = WOT ... this is a bit simplified though)
If the previous owner tuned the Volumetric Efficiency table for speed density and copied the high octane ot low octane ( or is running a custom Speed Density OS in the PCM) then it'll run fine w/out the MAF and if tuned properly you won't lose any power... maybe even gain a small amount.
However if the car wasn't tuned to run in Speed Density then you'll notice the following:
1. Low Timing
2. Poor idle characteristics and/or poor fuel economy
3. hard 1-2 and 2-3 normal driving shifts (stock configuration on 00 and earlier causes 100% line pressure in A4s when in failover)
When you say it felt stronger before... wsa that because the shifts were occurring really quick/hard? both WOT and part throttle?
May want to askt he previous owner if he tuned it for speed Density
If the previous owner tuned the Volumetric Efficiency table for speed density and copied the high octane ot low octane ( or is running a custom Speed Density OS in the PCM) then it'll run fine w/out the MAF and if tuned properly you won't lose any power... maybe even gain a small amount.
However if the car wasn't tuned to run in Speed Density then you'll notice the following:
1. Low Timing
2. Poor idle characteristics and/or poor fuel economy
3. hard 1-2 and 2-3 normal driving shifts (stock configuration on 00 and earlier causes 100% line pressure in A4s when in failover)
When you say it felt stronger before... wsa that because the shifts were occurring really quick/hard? both WOT and part throttle?
May want to askt he previous owner if he tuned it for speed Density
Thread Starter
Teching In
Joined: Sep 2005
Posts: 6
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yeah the shifts were going in hard. For example when i was going about 20 i would floor it,when it would hit second gear the car would not only peel out more but it would also fishtail. with the maf hooked up it still peels out in second but not as much
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
ok... not sure why the previous owner would have unplugged the MAF then... but you'll want to leave the MAF plugged in... when it's in failover it forces 100% trans line pressure all the time... it may feel good , but it's not the best thing for the transmission.
Also as mentioned if it wasn't actually tuned specific for speed density, you'll be running using the low octane timing tables (which drop ALOT of timing out... )
Also as mentioned if it wasn't actually tuned specific for speed density, you'll be running using the low octane timing tables (which drop ALOT of timing out... )
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TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
Correct, leave it plugged in... if the car wasn't specifically tuned for Speed Density (which most that tune for SD leave the MAF connected, and just disable in software) you'll lose a good amount of power (the increase you felt was probably just because of the much harder shifts)
Generally not a good idea to run 100% line pressure 100% of the time.
He may have had a MAFT hooked up, and when he removed it he forgot to plug the MAF back in
Generally not a good idea to run 100% line pressure 100% of the time.
He may have had a MAFT hooked up, and when he removed it he forgot to plug the MAF back in
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