I have had this car from new since Sept. 2000 (pre face-lift model) and have covered 69,000 miles without trouble, however, in the last week or so, I have noticed that the car is VERY reluctant to rev beyond 2,800 to 3,000 rpm in fourth and fifth gear (sometimes third also). The car acts as if the boost is being lost. It is worse if the car has a high load (going up-hill). It will keep accelerating beyond 3,000 rpm towards the red-line, but it is a real struggle.
I have read literally hundreds of posts about similair problems with VAG TDI (PD and non PD) engines and although nearly all blame the MAF sensor, this seems very inconclusive. Several people report changing this makes no differerence or that it works for a short time (maybe a week) before the problem returns!
I have cleaned the MAF (and the whole airbox/airfilter) and this makes no difference. I have run the car with the MAF disconnected and the car has absolutely "no go" whatsover at any revs, (can MAF sensors fail at just high flow rates?) Please note the car goes as normal upto 2,800/3,000 rpm, but is totally hopeless at all engine speeds with the MAF disconnected.
The turbo variable geometry linkage is working okay as the control rod moves a considerable distance if the vacuum pipe is disconnected with the engine running.
I belive the "N75" or "N18" solenoid valves can fail? Do these symptoms suggest this?
What I'm really asking, is does the symptom of the loss of power ONLY above 2,800 to 3,000 revs (when pulling high gears) give rise to the problem being definitly one (or more) particular component failures?
I will be having the car put onto a Bosch diagnostic tester later in the week, but again I have read lots of posts where this does not show any conclusive results.
P.S. The economy is not affected, it still does 52 to 56 MPG.
Any help MUCH appreciated.
Edited by Dynamic Dave on 20/05/2008 at 11:25
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The symptoms you describe do point to a MAF problem. I may (probably!) be corrected, but I thought a MAF sensor was constructed similar to a open ended fuse. Air runs past the metal "fuse" which indictaes how much air is going in. This will send info which in turn adds correct dosage of fuel and also signal whether to open the wastegate or not. It seems to me in your case that when it hits 2800 rpm, the "fuse" sends information which is interperated as causing to much boost and opening the wastegate to ensure the turbo doesn't blow.
I would say it was still a MAF problem.
I am not a mechanic, but I have had a MAF sensor problem and this is how I interperated it, but I bet I will be blown out of the water in a few minutes!
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Could be either the maf or the valve. What do the diagnostics say ? It may or may not show up.
Bosch do what are supposedly 'reconditioned' mafs at a fraction of the new price - the one I got for the volvo recently was indistinguishable from a new one (and £100 rather than £250+vat from the dealer). Alos you can get a pierberg sensor to fit in the bosch fitting for about £50. (not as accurate as the bosch one but more reliable, gives slightly worse performance, slightly better fuel economy)
How much are the valves ? Both the valves and the maf are common failure points you might want to replace them all. If you do then keep the maf, having a spare that partly works is better than nothing if you get a total failure on one. (On our A4 there have been at least 3 mafs in 3 years)
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This link might help diagnosis, if you haven't already seen it:tdiclub.com/TDIFAQ/TDiFAQ-8.html#e
You might want to check out the vacuum connection to the VNT according to their method, as its the whole set-up including the operation of the vacuum hose in-situ that needs to be considered.
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my father had the same symptoms with his passat 115 pd tdi.After a lot of trial and error it turned out to be the Exhaust gas recirculation (egr) valve. it wasnt cheap at £150 from vw but euro car parts /gsf dont stock them unfortunately!!
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No wonder VW/Audi are deteriorating in the JD Power reliability reviews.. Reminds me why I decided to never buy another one.
madf
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Thanks to everone who replied on this topic.
It turned out to be the "good old" MAF sensor afterall!
My local BOSCH service centre actually tries new parts after an initial diagnosis road test, (with the BOSCH computer attached). If this new part does not change the problem, they remove it and try something else, so no paying-out for items not necessary. Good service or what!
Interestingly, the diagnostics were NOT conclusive, but only pointed to the MAF being slightly off the normal readings.
The difference when the new MAF was fitted was very obvious even at lower engine speeds, so although the sensor had not totally failed, it may have been getting gradually worse?
Total cost (exc. VAT) £40 for the diagnostic (and fitting the new sensor) and £74 for the new MAF (Bosch exchange part). The VW price for the MAF is £75.10 exchange, so I'm happy.
Any one in the Merseyside area try Kirk Engineering 0151 933 4603. Passing their info. on to others is the least I can do after reading some of the nightmares other VAG drivers have had with TDI power loss problems.
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Last year my car had flat spot whereby from about 2,500 - 3,000rpm it seems to go flat and felt like there is no turbo. Once it clears 3,000rpm it goes but not as fast as it used to. I fixed the problem by replacing the MAF and every thing was fine after that.
Recently the car has developed a peculiar flat spot problem. From time to time when I need to accelerate and push my foot down the car does not respond at all. If I hold the foot down for a while (may take 30 seconds to a minute) suddenly the car responds and starts to accelerate.
Other day I was driving on the motorway at about 70mph in 5th gear behind a lot of traffic. Suddenly the traffic in front of me cleared and the car in front speed-up. I tried to do the same but my car would not respond. I can feel the engine would not rev-up. I changed the gear to 4th gear and the car still would not respond and continued at the same speed.
The strange thing is that it doesn?t happen all the time. Has any one got any idea what the problem might be? I am worried to take my car to VW garage. I have some bad experience with them.
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Hiya,
I had a similar issue with my car last night when I was driving from up North. Though mine is an automatic, the car stopped responding to accelerator. We have to be towed away by AA.
Now my mechanic syas there is no problems with the car and even the computer doesn't detect anything. I'm also reluctant to take mine to a VW garage.
Please would u advice what happened to yours next. Any diagnosis and resolution info will be greatly appreciated.
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I have audi A4 1.9 TDI I had a similar problem. I put it into a garage. I was informed it was something to do with the turbo as the varable vanes had seized and would not move when required. I would be driving along and the car would go into :limp mode: I would stop the car restart and all would be well for a short time then limp mode again. I bit the bullet and bought a turbo hay presto now goes great back to its auld self. Hope this may help apparently there a forum on this identical topic . I read it before parting with £700 however should be good for some time now. Now back to solving my lumpy idle and holding back until about 2000 rmp any ideas I have been told that an injector on cyl 2 has a different reading to the rest well £500 this time all the best
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Had similar problems with my car. Took it to one garage in Southampton and they replaced a lot of parts without curing the problem.
Took it to Express MOT in Southampton- FANTASTIC!!!! They have dealt with nthis issue many times before and the problem was resolved in no time.
So if you live in or near Southampton and have these problems give them a ring. Their number is 02380 633200
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