I have a late 1994 Audi 80 1.9 TdI.
I suspect there may be a problem with the turbo. Under acceleration in 1st and 2nd, it will rev freely to about 5000 rpm (redlined at 5200), of course like any turbo delivering the max power at about 2500-3000.
However in 3rd and 4th the power stops at 4100 - just suddenly as if there is some kind of regulator or cut out. Actually quite nasty as the first time it happened I was blatting up a hill on a motorway passing some slower vehicles and suddenly, no more power! The guy behind me must have thought 'what a wally'!It keeps going but there is no more acceleration. No doubt someone will say I should have changed up before hand, but there is still, in my opinion a problem.
However as this is my first Turbo diesel (in thirty years of motoring) I am a bit wet behind the ears on this particular topic.
I've found some contributions elesehere in the forum about sitcking turbos etc, but as mine seems to work perfectly well other than the symptoms above, I think this is an unrelated problem.
I'd be really grateful for any help here!
Thanks
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At the point you describe the 'turbo sticking' the turbine impellers will be spinning at 80-90,000rpm, things stick when stood still, not at that speed (which equates to a turbine blade tip speed of around 700mph!) If it did stick it would explode, I would replace the fuel filter, and check all the air duct after the turbocharger, but to be honest, there are loads of things it could be, just check all the simple things before resorting to £££££s.
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You may find that the power curve drops so sharply after 4000 that it feels regulated.
My old Xantia (my first TD) did exactly the same thing, once I stopped treating it like a petrol engine - no problem.
Do you get lots of black smoke when the symptoms occur?
I'd check the air filter - at 4000 rpm the engine will be drawing in the maximum amount of air, if the filters less than perfect this may affect the fuelling.
If there is a fault, its more likely to be the air mass sensor which measures the amount of air going into the engine and adjusts the injector timing accordingly.
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I had exactly the same problem 18months ago with my 95M 80 TDI with 25k miles.
After a number of checks by Audi agent which diagnosed ECU etc they found that it was a sticking wastegate. £1350 for a new tirbo as they are a sealed unit!
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...If you paid that for a turbo, then I'm afraid you got ripped off!
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Well, thank you all for your contributions. I am no closer to a diagnosis but later this week will take the car for a spin on the motorway with a mechanic friend and we'll go over these possibilities.
I certainly hope it's one of the earlier solutions, not a new turbo that's needed, but £1350 does seem a lot for a turbo.
I am also aware that maybe I should stop expecting it to react like a petrol car and this may be a valid point. As I say, my first turbo diesel and I've only had the car a few days.
I'll post any further developments here, could be useful to someone else.
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I agree, I have had VAG cars for 20 years and this is my last.
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Mine had exacly similar characteristics in 3rd and above. I don't think anything is wrong except be aware of need to change up when (or just before) the power went AWOL, at just over 4000rpm. Always did 50-55mpg so I took it as a trait of the TDI.
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The many VAG Tdi 90/110 bhp diesels I've driven have all had the rev limiter set at approx 4600rpm - none reached 5000+! From memory, the Audi80 Tdi had a particularly sudden cutoff; later models the limiter action was slightly softer. You should be able to go over 4100rpm in 2/3 gear - but as you say, power and torque drops significantly from 3500+. Could it be the common culprit, the air mass meter?
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Again, thank you all for your contributions.
I went for a drive with my mechanic friend, who tells me all is well apart from a bit of a flat spot at about 4100 which is what I'd picked up on. He's going to look at that at some time. The point really that comes out of this is that I am not used to TdI performance and as someone said, was half expecting it to react like a petrol car.
I am not a racer, my only concern really was safety, for those situations where you need power, and that it would get worse.
I suppose also I needed reassurance that I hadn't bought a lemon!
Great forum, a really useful resource, and thank you all.
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This may not be the cause but I had a Nissan 200SX many moons ago which developed a fault very similar to that you describe.
It transpired after much phaffing about that the fuel filter was partially blocked thereby "retarding" the performance.
Regards
Mutley
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Just when I thought it was safe to go on the motorway .......
I took the car for a serious run this weekend - 1300 km round trip. Same problem as described above, and it seems to point to air mass meter as per a couple of other threads on this forum. At about 140kph/85 mph (no speed limits on the German autobahn!) I would sometimes find myself with no acceleration, also the car would slow down going up hills, when it should have plenty in reserve. BUT here is the odd bit, backing off on the accelerator and then easing it down again would suddenly make the power pick up.
Also the delivery is not smooth and even on a trailing throttle the engine feels jerky. I am trying to hope that it is just a blocked fuel filter or dirty injectors - is this likely? (I will change the fuel filter during the week to check out that theory).
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One air mass meter later, problem remains.
The VAG dealer tells me that the problem is, as far as I can understand with my limited French, the 'computerised diesel injection pump' and is quoting me 1500 Euros (a thousand pounds!!) to supply, fit, and set up a new one.
They charged me 200 Euros for the Air Mass Meter, which is (given the ripoff prices of most things in France) reasonable in comparison to the UK price, but I am at a total loss to comprehend what they are talking about and what this price corresponds too. Can anyone help? Please!
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I'd have a look at the EGR valve, myself.
Often, the cheapest way to disable it is to make two steel 'gaskets' in order to isolate the valve. I have done this twice on 80 TDI's with startling results.
The AMM on the 80 TDi was/is a reliable unit, not like the Bosch ones fitted to later 110 engines. I have the Pierburg AMM on my A4, thankfully - these don't give trouble.
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