Maf replaced symptoms remain!!

[Mosschopz]

Hi the power loss problem on my 99 2.5 tdi A6 continue,

Tried taking the MAF sensor off at the weekend...it solved the problem, all the power was back runniong like a dream. So i purchased a new MAF bunged it in and...same as before!

Anyone shed any light on this??

How bad is it to run the car without the sensor, surely the car is getting the wrong mix anyway at the moment.

Thx

[Crasher]

What is the problem? I missed your previous posts.

[Mosschopz]

The car wont pull much at all, its was ok on flat and terrible up hills, i read alot about the maf sensor and how u could remove it to see if thats the problem, before i did this i booked it into autotechnics (vw audi specialists) who told me they suspected the fuel pump (quoted £1300 fitted) after the shock of the bill i had a look at the MAF for myself, removed it and the car ran like i always thought it should ( i havent had it long at all) it pulls right up to the 100 mark and beyond, and the turbo can clearly be felt too.

Thing is i assumed that meant faulty MAF i replaced it (£68 GSF) but the symtoms remain the same. With MAF gutless no power, MAF removed runs really well!!

any ideas?

The engine is obviosly having an issue with the air/diesel mix when the sensor is in place and the MPG is worse too.

With the MAF off the car runs so much better and the economy goes up!

If it is bad to run the car with the maf disconnected because of the fuel mixture or economy then it must be just as bad with it on right now??

[Lex Luthor]

Find someone local to you who can check it out with VAGCOM.
Try not to poke-and-hope any more as it can become expensive !!!

[a8 tech]

2.5 You Say Mmmmmm Turbo I Say Common As Muck.Check the boost reading from rolling start 1500rpm 3rd gear fooot to the floor and all will be revealed,it is unlikely to be the pump and i would expect a fault boost lower limit or exceeded also check the wastegate arm is moving over the full amount of travel

[Mosschopz]

Thx Lex but thats exactly what i did do ,

they didnt mention the maf ..just a £1300 bill for a new pump!

the results i have from there computer are:

'Start of injection control deviation

The fault clears then comes straight back

connect fault code reader directly to back of pump code 57 is stored with no text. The code will not erase

Suspect that diesel pump is U/S

The cambelt and injection pump belt also need replacing'

if its the pump then why would it work fine with the maf removed?

[ini]

What is the make and part number of your relacement MAF?

Did you check whether your static injection timing is within range, and not to far retarded?

If it runs OK with the MAF disconnected (default map), it is unlikely to be the EGR stuck open or similar problem.

Have you checked all the MAF wiring harness for breaks/shorts, and the MAF connector for faults?

Have you been using a tuning box?

I would suspect injection pump timing, or electrical fault to MAF.

[a8 tech]

I suspect you have a sticking vain in the turbo.The commencmant of injection is pointing to the fuel pump timing out due to belt slip.By disconnecting the maf you have a unregulated boost to the turbo and defult fueling so you need the turbo boost checking and the fuel pump timing checking before you continue

[Mosschopz]

The MAF is a straight swap for the old unit

Bosch 18790A
0 986 284 005
0 281 002 429

Am i right in thinking that because it runs fine without the maf the injection pump itself is ok ? If so i should let the garage know of my findings so they can continue eliminating things.

Not sure how to check the MAF wiring/connector for faults although i did notice some of the plastic inside the MAF connection plug was damaged...only a small bit, the pins seemed fine.

I have not been using a tuning box.

How is static injection timing checked?? is this something i can do?

Are there problems with running without the MAF in the meantime (deault map as you call it)

[Crasher]

If you have access to VAG-COM or something similar, go into Basic Adjustment mode 04, sub group 011 with the engine running. As the display changes from ON to OFF in zone 2, you should be able to watch the turbo vane actuator arm operate. If not, a gentle tap on the arm when the display is showing ON can encourage it to operate. Otherwise, it means a new or rebuilt turbo which is very common on the 2.5 V6 TDI. As the other chap mentioned, unless the AMM you used was genuine, I would take it back and get a genuine one and even these can fail immediately. If it is a Bosch branded item from a well known supplier, almost every one I have ever had was faulty straight out of the box. We get through lots of AMM's and we only use genuine VAG.

[a8 tech]

If you have electrical problems at the air mass you will store faults signal to small short to posotive short to earth.If the statis timing is out you will have delayed start up and you will need measured value blocks to check.I would tell your workshop of your findings so they can check boost pressure for possible links ie sticky turbo intake pressure sender or boost pressure control as i would say your fault is related as boost readings can have a reaction to fueling or reduction in fuel metering from ecu to prevent over boost and damage to engine.

[Mosschopz]

where can i get a genuine vag mass air sensor (UK)

Can someone explain why the car can run fine with the sensor disconnected? doesnt this mean everything else is ok?

What damage can i do running the car with the sensor disconnected?

thanks

[Crasher]

You local Audi or VW dealer!

[ini]

If the car really does run well with the MAF disconected (it should not run better than with a good MAF), then as you suggested, the fuel pump and turbo etc may be ok.

The evidence does seem lead to either the new MAF being dodgy, and/or something causing mechanical or ECU related fuel restriction/timing retardation.

Has the fuel filter been changed recently, and has any other work been carried out on the fuel system that could cause an air leak.

[Crasher]

Has it had a fault code read? If you have this done now, disregard any faults pertaining to the AMM, this is why I tell people to never disconnect anything with the engine running as it produces spurious fault codes.

[tut_gareth]

this is a long shot...... Is your car automatic?

a work collegue of mine had similar sounding problems on his 2.5 tdi A4 and it turned out to be the gearbox ecu going into limp mode ( for some reason or another) and causing all sorts or power loss and engine running problems.