Resetting ECU after cleaning or replacing MAF??

[EmmettC]

Hey everyone,

i'm having problems with the Turbo on my 98 A4 1.9 TDI, theres a loss of power which i noticed occurs at around 3000 revs. I figured its a problem with the MAF (Mass Air Flow Sensor). (Or maybe a pressure sensor....if any of ye think any different feel free to let me know...)

So instead of getting a new MAF i decided to clean the one in it with carb cleaner, but it did'nt make a difference.

I'm just wondering would it now help to reset the ECU?? Or is resetting the ECU only required after a new MAF has been installed?

Yer help would be greatly appreciated

Thanks

Emmett

[AutoTDI]

Before changing any sensors, you should scan for fault codes using VAG-COM or other diagnostic software. It may be the MAP sensor at faullt, or it could be the turbo, or plumbing. I've not heard of any need to reset the ECU following sensor replacement. Also, have a look at this thread: http://www.vwaudiforum.co.uk/forum/showthread.php?t=18322

[EmmettC]

Thanks for the help, from reading that thread, he seems to have similar symptoms to mine... I did have car checked for faults and it threw up fault codes on the MAF and MAP

I've cleaned out the MAF, and i think its slightly better since then but it still dies at round 3000rpm. So i think i'll give a go at cleaning out the MAP. I think its more likely to be the MAP than the MAF somehow.

I've a 98 A4 1.9 TDI 90 BHP, but i've been told its a 97 model car, so where is the MAP located on this car? Is it on the ECU??

Thanks

Emmett

[AutoTDI]

My car is a 97 model and the MAP sensor is located within the ECU. If you look at the underside of the large diameter black manifold pipe between the engine and the firewall, you will see a thin black flexible plastic pipe which eventually finds its way into the ECU. Nearby, you will notice an electrical sensor lead which conveys manifold air temp to the ECU. On later models, I understand that the MAP and temp sensors are integrated within the manifold, with only electrical links to the ECU.

[EmmettC]

Thanks for the help, went to have a look there but did'nt get enough time, flippin torch went dead!

So just for clarification, is the MAP sensor underneath the black plastic cover where the ECU unit is located or is it inside the actual metal housing of the ECU?

Thanks again

Emmett

[AutoTDI]

Sorry, can't answer that question - haven't got that far myself yet! However, I understand it looks like the attached photo:

[pete99]

take a look at my old posts re- MAFM.
Its a sensitive instrument - even cleaning it can disturb it .
If you buy a new one - PLEASE dont go for the cheaper ones --it HAS to be a bosch you buy.

[ini]

This is the 97 type board mounted MAP.

http://i118.photobucket.com/albums/o99/inisj/DSC00112.jpg

On the pre-98 cars the MAP is much less likely to fail, as it is safely away from the heat/cold and vibration of the engine. If you can see crud in the transparent tube that joins it to the ECU body it may be damaged.

If there are no pressure or vacuum leaks in the management system, 3000rpm boost loss is more likely to be MAF, sticky VNT, or partially blocked CAT related.

[EmmettC]

Hey, thanks for the advice. I've just ordered a new pierburg MAF, so when i fit that i'll let ye know how i get on. If there is no difference once i fit the new MAF, i'll now it could be the MAP, or like you said, vacuum leaks, or VNT mechanism

When fitting the MAF, is it just a case of taking out the old one and fitting the new? Is there anything else required like clearing fault codes or reseting the ECU?

In the mean time i'll check the MAP out for dirt etc....

Thanks

Emmett

[AutoTDI]

ini - your photo of the MAP sensor looks a lot different to mine. How is it secured to the board? Does it need to be soldered in?

[ini]

If i remember correctly, it had three pins, through-hole soldered to the top board.

It is just a standard design pressure sensor inside the box.

It looks very similar to this design:

http://i118.photobucket.com/albums/o99/inisj/map.jpg

[AutoTDI]

Thanks for the info, ini. Just wondering what to look for when I take the lid off and also checking that I buy a compatible replacement. At the moment, I don't seem to have a MAP sensor problem as the cleared fault codes have not returned and the engine runs fine.