2001 - (Y) 100BHP Passat Below Full Power Fault - Diagnosis Help Please!

Hi all

I'm a relative newbie on here, and am trying to diagnose what i believe to be a fault with my Passat.

It's definitely low on power, and I don't think the turbo's working properly - let me describe. She starts and drives about town ok - in the 0-50mph range she's fine, but certainly not quick. However, it's on the motorways, and at 65 - 85 MPH that this the problem is most notable.

She'll cruise comfortably enough on the flat at 65-80mph, however, as soon as she sees anything remotely approaching a steep hill - she's flumoxed! To give some regional examples;

From Maidstone towards Canterbury, heading east on the A249, there is a reasonably steep hill up towards the Kent County Showground. As soon as you get past the speed camera, and start up the windy part of the hill, she's struggling - she'll drop from 65, straight down to 55 and 50 - and then down to 45 by the time you get to the top. It doesn't matter if you keep her in 5th of 4th, and with the throttle on the floor - she just won't go any faster.

Example 2, is on the A2, from Brenley Corner (where you either go to Margate or Dover), and then head up the long(ish) drag up towards Canterbury, again, she'll drop slowly from 70+, down to 50. I can only just keep up with articulated lorries going up the same drag.

I'd like to diagnose and fix it myself, but am not sure what to do. She's regularly serviced (done 101k miles), and in good (although clearly not perfect) mechanical order.

From my own reading around, it seems like it could be either:

1 - a split/broken vaccum pipe somewhere in the system
2 - the air flow mass thingyme (tho I don't acutally know what this is or does!)
3 - the turbo's shot and doesn't work properly.

I used to have a Passat Sport (02 - 130bhp model) as a company car, and I know what the turbo sounds like when you're giving it a bit of shove, and I certainly know how quick it went... Mine's a world apart from that 130 bhp model, and I'm sure I can't hear the turbo whistling when I would expect it to be kicking in at approx 1800+ revs through to just short of 3,000 revs.

If it helps, I am getting ok fuel consumption - she's driven extremely economically, and averages 65mph on most motorway journeys. I'll usually get a av consumption of between 48 - 52 mpg on the computer, and somewhere between 600 - 640 miles out of a full tank of fuel

Can anyone suggest what else I should be checking, and how to diagnose what the fault actually is - I'd prefer (purely for the satisfaction) of being able to do this myself, but am concerned that I won't be able to without a damn diagnostic computer!

Your help would be very much appreciated!

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Originally Posted by rjsdavis

Hi all

I'm a relative newbie on here, and am trying to diagnose what i believe to be a fault with my Passat.

It's definitely low on power, and I don't think the turbo's working properly - let me describe. She starts and drives about town ok - in the 0-50mph range she's fine, but certainly not quick. However, it's on the motorways, and at 65 - 85 MPH that this the problem is most notable.

She'll cruise comfortably enough on the flat at 65-80mph, however, as soon as she sees anything remotely approaching a steep hill - she's flumoxed! To give some regional examples;

From Maidstone towards Canterbury, heading east on the A249, there is a reasonably steep hill up towards the Kent County Showground. As soon as you get past the speed camera, and start up the windy part of the hill, she's struggling - she'll drop from 65, straight down to 55 and 50 - and then down to 45 by the time you get to the top. It doesn't matter if you keep her in 5th of 4th, and with the throttle on the floor - she just won't go any faster.

Example 2, is on the A2, from Brenley Corner (where you either go to Margate or Dover), and then head up the long(ish) drag up towards Canterbury, again, she'll drop slowly from 70+, down to 50. I can only just keep up with articulated lorries going up the same drag.

I'd like to diagnose and fix it myself, but am not sure what to do. She's regularly serviced (done 101k miles), and in good (although clearly not perfect) mechanical order.

From my own reading around, it seems like it could be either:

1 - a split/broken vaccum pipe somewhere in the system
2 - the air flow mass thingyme (tho I don't acutally know what this is or does!)
3 - the turbo's shot and doesn't work properly.

I used to have a Passat Sport (02 - 130bhp model) as a company car, and I know what the turbo sounds like when you're giving it a bit of shove, and I certainly know how quick it went... Mine's a world apart from that 130 bhp model, and I'm sure I can't hear the turbo whistling when I would expect it to be kicking in at approx 1800+ revs through to just short of 3,000 revs.

If it helps, I am getting ok fuel consumption - she's driven extremely economically, and averages 65mph on most motorway journeys. I'll usually get a av consumption of between 48 - 52 mpg on the computer, and somewhere between 600 - 640 miles out of a full tank of fuel

Can anyone suggest what else I should be checking, and how to diagnose what the fault actually is - I'd prefer (purely for the satisfaction) of being able to do this myself, but am concerned that I won't be able to without a damn diagnostic computer!

Your help would be very much appreciated!

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Get a Vag Com lead and download the trial version to check for fault codes. If you don't have a laptop then I would suggest removing the EGR and inlet manifold and cleaning them (could be restricted airflow due to carbon/oil residues) The air mass meter is located under the plastic cover on the air filter housing, held in by 2 security screws, it can be cleaned with an electrical cleaning solvent then blown dry. The turbo has a vacuum controlled actuator, the rod from this onto the lever which moves the vanes can be seen to lift when the engine is revved. If the rod does not move suck on the pipe going to the vacuum actuator, the rod should lift then drop when you release the vacuum (if it don't it could be stuck vanes and the turbo will need cleaning). If there is no vacuum there it could be the control valve (N75 I think) or loss of vacuum due to leaks or duff tandem pump.

Thanks Caldirun

I follow everything that you're saying, and it all logically makes sense in my brain - the trouble is, that I don't my way around the engine bay well enough to know where all of the parts (EGR / air mass meter / turbo actuator etc etc) actually are!

Is there a set of engine bay maps anywhere on the web? If not, I suspect it will be a Haynes manual job to find everything that you've suggested....

Thanks again.

Richard

Don't do anything untill you have a code read. My money is on a turbo fault or a fault in the turbo actuation. Without a code read you are wasting your time. Given your fuel figures its is highly unlikely that you have an egr or air mass meter fault. I bet a code read will say turbo pressure too high.

Thanks Martin...

Someone else suggested simply disconnecting the Air Mass Meter, and driving the car like that... I did it at lunchtime, and it does seem to have far more low end grunt with it disconnected, but this was only "round town" type driving.

I'm saving it for the motorway run tonight to really see (on the roads where I experience the biggest lack of power), to see if there is a difference. Fingers crossed.

In respect of your suggestion - should it turn out to be a turbo fault, or turbo actuation fault, would you expect it to be a "replacement parts" type job (likely to be pricey), or a damn good cleaning and service type job of the offending parts that are letting me down currently?

Richard

It's poinltless disconnecting the AMM. Now you will have a fault code because you disconnected it. It won't tell you anything because the car is designed to run using it's sensor feed so it obviously runs different if you disconnect it. Get a code read.

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Originally Posted by martin1810

It's poinltless disconnecting the AMM. Now you will have a fault code because you disconnected it. It won't tell you anything because the car is designed to run using it's sensor feed so it obviously runs different if you disconnect it. Get a code read.

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Funnily enough, this is what someone else recommended I try yesterday - unplugged the MAF at lunchtime, and on the way back home this evening, it was like a little rocket (by comparison to what it had been like). Loads more power coming off roundabouts in 2nd... Loads more power off the line, loads more speed gathering power to accelerate from 70mph up in 5th gear etc etc.

It even felt faster when my foot was off the throttle. You know when you come up behind a car on the motorway and you simply take your foot off to scrub off some speed? It would keep going (effectively almost freewheeling), even with nothing on the throttle and would scrub off speed far less quickly than it used to.

Plus I noticed that it would stall much later than it was too. You know when you come to a dual carriageway roundabout where you might be slowing down (in 5th), from 50+ mph. It would get to the edge of stalling far, far later than it would before, and where you needed to dip the clutch to stop it.

Overall, it would appear that my MAF is mullered, however, I'm not sure that this is the only problem. I re-did the old Canterbury route and took the long drag up the A2. This time, it held 70 mph (on the cruise control) all the way up rather than losing speed gradually this time - HOWEVER, I still think that a healthy TDI should be able to accelerate and gather speed whilst going up this same drag (either in 4th or 5th), but mine wasn't capable of that.

As the AMM supplies the ecu with air volume information, disconnecting it would screw up the fuelling. I would expect it to drop in to limp mode, but it obviously didn't.

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Originally Posted by rjsdavis

Thanks Martin...

Someone else suggested simply disconnecting the Air Mass Meter, and driving the car like that... I did it at lunchtime, and it does seem to have far more low end grunt with it disconnected, but this was only "round town" type driving.

I'm saving it for the motorway run tonight to really see (on the roads where I experience the biggest lack of power), to see if there is a difference. Fingers crossed.

In respect of your suggestion - should it turn out to be a turbo fault, or turbo actuation fault, would you expect it to be a "replacement parts" type job (likely to be pricey), or a damn good cleaning and service type job of the offending parts that are letting me down currently?

Richard

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Hi

Can I suggest that you follow Martin's advice - I had a similar problem, took advice from Martin & Crasher - code read diagnosed overboosting turbo - removal, re-building (by Midland Turbos) and re-fitting by local independent was £500 all in. Between them, they saved me £1000!

Hope you get sorted

Regards

Laurie

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Originally Posted by Laurie2212

Hi

Can I suggest that you follow Martin's advice - I had a similar problem, took advice from Martin & Crasher - code read diagnosed overboosting turbo - removal, re-building (by Midland Turbos) and re-fitting by local independent was £500 all in. Between them, they saved me £1000!

Hope you get sorted

Regards

Laurie

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Thanks Laurie

But am hoping that its not going to cost anything like £500! That would be a bloody disaster..... (just before Christmas!)