2002 Audi A4 TDI Sport - Loss of Acceleration

bob2oo7

Hi guys

I have a 2002 Audi A2 TDI Sport (130 BHP)

Always looked after, serviced regularly etc.

On Saturday I started to loose power when accelerating, then it would come back, then go again etc.

When its gone its very sluggish, I wouldnt attempt to over take anyone. Sometimes it just comes back without warning, other times I have to restart the car

It was fine this morning coming into work, no issues

Can anyone point me int he right direction, is this something I can sort out myself so I can save money?

Thanks in advance

George Dalton

Limp mode, very common issue with them. There are a number of causes, some very simple and cheap to sort out, some not so cheap.

The best thing you can do IMO is find someone who knows their way around the car in question and pay them for an hour of their time to diagnose the cause. Otherwise you will probably just end up spending money on parts that you don't need.

bob2oo7

Thanks for the reply

If I get the car on the computer will that tell me where the fault is?

yop

As above get a diag done on it.
Can be sensors, injectors etc.

George Dalton

bob2oo7 wrote: »

Thanks for the reply

If I get the car on the computer will that tell me where the fault is?

The scan will give a general fault code which indicates why the limp mode is happening, in this case it will most likely be related to turbocharger boost levels, either under or over-boosting. The fault code will indicate under or over-boost but that information by itself isn't going to tell you what part needs changing (if any)

It is up to the mechanic to test the relevant components to establish exactly where the fault lies.

vectra

Vacuum hoe off or cracked?

ION08

MAF sensor?

yop

ION08 wrote: »

MAF sensor?

Can be one of more sensors, can be the EGR if there is one in the Audi, can be injectors, can be dirty diesel.
The computer will tell the tale and cost less in the long run.

bob2oo7

Tell me more about Dirty Diesel, as I have heard some stories about the petrol staiton that I go to, but didn't pass any remarks about it.

Is there anything I can do myself to clean, diagnose if this is in fact the case?

bob2oo7

VAG Come Results:

17994 and 17552 Both unrelated

The bIg one:

17965
-Charge Pressure Control: positive deviation
-Intermittent

Anyone experience this one before?

bob2oo7

17965/P1557/005463 - Charge Pressure Control: Positive Deviation
Possible Symptoms

• Reduced power output
• Limp mode

Possible Causes

• Boost Pressure too High
• Hoses/Pipes incorrect connected, disconnected, blocked or leaking
• Charger Pressure Control defective
  • VNT (variable nozzle turbo): nozzles stuck
• Solenoid Valve for Boost Pressure Control (N75) defective

Possible Solutions

• Check Hoses/Pipes to/between Components
• Check Solenoid Valve for Boost Pressure Control (N75)
• Check / Clean / Replace Charge Pressure Control
  • Check / Clean mechanism for variable nozzles

Chimaera

Did the person who scanned it clear the code?

I've had my car go into limp mode occasionally and once I cleared the code the problem didn't come back. It can just happen sometimes that things go a little haywire and it all settles down again.

But that being said, start by having the vacuum checked. Any leaks or other faults there can cause problems. The vacuum actuates the EGR, N75, brake booster so if it's flaky all of those components will be affected.

Get a log done of MAP requested vs MAP actual (VCDS will need to be plugged in while driving for this). If there's a major discrepancy between these too you are down to faulty MAP or faulty VNT system. If the MAP actual value remains constant no matter what way you're driving and no matter what the ECU is requesting, the MAP sensor is dead.

If MAP actual is varying but not agreeing with MAP requested then it's worth looking at the VNT system. Two things can happen here. One is the vanes in the turbine housing can get gunked up with carbon deposits and jam open or shut. If this happens, the car will be permanently going back into limp mode each time the codes are cleared. The solution here is to open up the turbine housing and poke out the carbon buildup.

The other possibility is a failure of the VNT actuator. This might be due to the vacuum system being messed up, hence mentioning that as the first possibility. Alternatively, the N75 might be gone south - this can be checked quickly if you can borrow one from a known good car. Or the vacuum actuator on the VNT is dead. Depending on the turbo you have, the actuator may be replaceable. I can't remember the specific values, but there's a test for the actuator which involves applying a known vacuum to the actuator and measuring how far it moves.

George Dalton

Good advice above.

bob2oo7

All this will have to be done by a mechanic

How much are we talking for this?

Chimaera

A lot of it is time, and how much of it you need to pay for depends on how long it takes to find the problem. If you're handy, replacing the vacuum lines isn't a big task. There are howtos online for it I'm sure.

darragh o meara

Have a read of this thread. I have advice to the poster on a similar problem I've seen on a few of these cars.

Unfortunately I don't have time to retype it on my phone.

May be of use to you and a cheap easy fix you could prob do yourself.

http://www.boards.ie/vbulletin/showthread.php?p=84788568

bob2oo7

Just an update

Got this sorted yesterday

First off the ERG valve was cleaned, and I took it back. Slight improvement but still terrible

Next step was to try a new MAF sensor - No Joy

Save the best for last - New Boost Pressure Sensor... and now the car is flying

Kells101

Can you send me the pic as we'll please