Loss of Power - AMM or Temp Sensor?

**Mid** · 05-08-2009,07:49 PM

Passat 2002 TDI Sport Saloon 73k miles

I took this car into Smashing VW's in Leeds for Service and MOT on Monday. The car was running fine when I took it in but when I collected it (having passed the MOT) there was an instantly noticeable lack of power - as if the turbo had been turned off. I can still get it up to 70mph eventually and fuel consumption is good but acceleration is very slow - about the same as my pushbike.

I took it back to Smashing next day and they put it on the computer and showed me/told me what was wrong. I didn't understand all of it but the gist was the Air Mass Meter and Temperature sensors were not working properly. From memory he showed me two temperature readings, one at 90 degrees (reflected on the dashboard) and one at about 60 odd degrees. He then also showed me some mismatching figures of something (air?). They were measured in 100's of something, one was perhaps 500 ish and the other about 300ish - he said they should have been the same and that meant the Air Mass Meter wasn't working. He then disconnect something under the bonnet, revved the engine, and said something along ther lines of "that's revving better already but look at the black exhaust smoke". I think this was supposeed to be confirmation that the AMM was faulty.

I was told the loss of power was a complete coincidence and nothing to do with anything they had done during the service and he offered to order the parts and fit them for me at my expense. I have no way of knowing whether this is genuine or a rip off and declined to let them do further work until I had investigated. (sorry for length of this , nearly finished)

I have removed the AMM and sprayed it with Isopropyl Alcohol to clean it(recommended in a forum post) but it has made no difference either way.

Can anyone tell me what is likley to be wrong, should I fit a new AMM, a new Temp sensor, both, go back to Smashing etc ??????

Help.

Mid

**martin1810** · 05-08-2009,07:53 PM

You need a fault code read if you want to check/confirm what the garage said. You could try asking on the vag-com section, to see if anyone is near you with the equipment.

**Mid** · 05-08-2009,08:19 PM

The garage said I needed both a new Air Mass Meter and A Temperature sensor and the figures on their computer validated this as far as I could see.

It just seems strange to me that the car worked perfectly when taken in but now needs two new components.

I was lead to believe that it was the AMM that was causing the power loss and that the faulty temperature sender was a secondary concern that probably wouldn't show itself until the cold weather came. Which is why I am trying to find out which component to fit first.

I was hoping that this information would be enough for a diagnosis, but perhaps not.

**martin1810** · 05-08-2009,08:28 PM

The air mass meter could fail at any time so perhaps it just has. You need to fit a genuine VW one to avoid future problems. Lots of aftermarket ones have proved unreliable.

**Mid** · 05-08-2009,08:49 PM

Any idea where to buy one, I've been searching the internet tonight and the cheapest I found was £65+vat but I don't know what make this was?

Cheers

Mid

**martin1810** · 05-08-2009,09:53 PM

VW dealer

**Laurie2212** · 05-08-2009,10:37 PM

Originally Posted by Mid

Any idea where to buy one, I've been searching the internet tonight and the cheapest I found was £65+vat but I don't know what make this was?

Cheers

Mid

Two years ago I replaced my air flow meter - easy enough to do (and my skills are limited) I spent ages searching the Internet and took notice of the forum members and avoided the offerings on e-bay. Tracked the cheapest to a local dealer - Andrew Page (believe they have branches all over) - the unit was a BOSCH - paid £90 and got £30 back when I took my old unit back - different car. Thought it had gone again recently, but a diagnostic revealed a overboosting turbo - but that's another story! If you have had a diagnosis, the air flow meter would be my first choice as your symptoms describe my experiences before the new flow meter was fitted. However, as Martin suggests you could try your VW dealer - my window regulator from VW was £10 cheaper than a second hand one from breakers yards - so this may be true for the air flow meter as well.

Hope this helps

Laurie

**Mid** · 06-08-2009,08:54 AM

Thanks , will try both.

Mid

**mr-mixalot** · 20-08-2009,04:16 PM

Hi I think I have the same issue as you, the acceleration when I'm in Drive on my V6 2.5 TDI is slow and sluggish, gets there eventually

If I use 'tiptronic' manual mode then the acceleration is much better

I'm no expert but does anyone thinks this could be a similar issue

Thanks in advance

**Laurie2212** · 20-08-2009,08:39 PM

Originally Posted by mr-mixalot

Hi I think I have the same issue as you, the acceleration when I'm in Drive on my V6 2.5 TDI is slow and sluggish, gets there eventually

If I use 'tiptronic' manual mode then the acceleration is much better

I'm no expert but does anyone thinks this could be a similar issue

Thanks in advance

Hi

The best advice that the expert forum members will suggest is that you get a diagnostic and fault code reading so that you can pinpoint the problem. It could be any one of a number of problems! By following forum member's advice I have just saved £1000 on a turbo repair.