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Thread: Golf 1.9 Tdi Unexplained loss of power

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  1. Golf 1.9 Tdi Unexplained loss of power 
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    Hello everyone,

    I had this problem and thought I could work it out but in the end I fixed it without knowing it. My post is a bit long but its a long story!

    The car is a low mileage 1.9 Tdi 66kW AGR engine with normal injection system. I changed the cam belt recently and, with a friends help, checked and reset the injection timing with VAG-COM. I was a little disappointed to find that although I had reset the cam timing and fine tuned the injection timing and the car started easier and ran smoother, there was zero improvement to the mpg which runs around the 59/60 mpg mark - I was hoping for more. Anyway, not too long after, and it was more of a feeling that I was missing power but as the weeks went by I noticed a very definite 'hole' in the pull of the engine between 2,000 and 2,500 rpm. This got worse and worse i.e. the 'hole' spread out each side until it felt really underpowered and overtaking became 'interesting'. I fitted a boost gauge to the inlet manifold and found very little to worry about, there was 1.0 bar max which did not peak particularly quickly but I was getting full boost. OK, it wasn't the turbo, so what was it? I decided to take the inlet pipe off and have a look up what would be the throttle body if it was a petrol engine and was shocked to see the amount of carbon caked all over the EGR valve port. The carbon build-up must have reduced the inlet by a third at least. I took the EGR valve off and cleaned it all out and scraped as much oily grot off the inside of the inlet manifold as I could reach. That's gotta be it, I thought. No, it wasn't. Still the same. I also disconnected and plugged the EGR pipe to stop it working and building up carbon again and later bought two blanking plates and took the EGR link pipe off altogether. Meanwhile the lack of power continued. OK, maybe the anti run-on valve is closing at the wrong time so I ran the car with that pipe off. No, not that. OK, maybe the rest of the inlet manifold is choked up with carbon so I took that off. No, it wasn't badly restricted really. Sure it was gungy in there but not overly constricted, the backs of the valves didn't look pretty either but getting he carbon out of there was not going to be easy. In fact having loose lumps of carbon could end in tears so I figured, best to leave them alone. Whilst the inlet pipe to the turbo was off I twizzled the turbo shaft - nice and free and there was no axial play so I reassured myself the turbo was definitely OK. I also put a camera down the cold-air pipe to the air filter in case a family of wrens had taken up residence - no, all clear. Anyway, put all that back together and . . . no difference! Even worse if that was possible. Now the engine would not rev past 3,000 rpm and I could not coax more than 0.5bar out of the turbo. I even took all the pipes off the boost control valve so there was nothing controlling the turbo at all and still it would not go over half a bar! OK, maybe the cam timing has slipped? The sprocket is only on a taper, not keyed at all, I couldn't really believe it but maybe it has crept round? Checked that - no, perfect timing still. Finally, whilst the air filter cover was off anyway I thought I'd look at the mass air flow meter. I unscrewed it, looks fine but seeing as though it was out, I would just clean the wire with a cotton bud and brake cleaner which resulted in a slightly brown mark on the bud then, dejectedly, I put it all together again. The next time I drove it BINGO, power and boost restored - it was a very, very slightly dirty wire on the MAFM!
     
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  2. Re: Golf 1.9 Tdi Unexplained loss of power 
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    I had a SEAT cordoba with an agr, I think this was the best diesel engine I've ever owned, relatively simple, great mpg, started on the button every time even at minus 20 in Scottish winter, I ran it for over 100k with only timing belts and service items to change, apart from the MAF with same symptoms as yours!
     
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  3. Re: Golf 1.9 Tdi Unexplained loss of power 
    #3
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    Hi Rob69,

    Thanks for your reply. I was at the end of my tether with this one, no fault codes but no power either and every great idea I had did not fix it. Now I am happy again, I can overtake tractors once more! Hooray!
     
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  4. Re: Golf 1.9 Tdi Unexplained loss of power 
    #4
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    Update.

    My power loss was never really 100% cured and my MPG was slowly, slowly, slowly going down each tank, I was down from a high point in the summer of 59.9 MPG down to 54 MPG. As I wrote about above, I wiped the edge of the meter blade and got some gunge off it and yes, a lot of performance was instantly restored but in the weeks that followed I still felt there was some oomph missing. There was nothing you could say for definite like a specific fault at a specific rpm but still it felt OK in first and second but as soon as some load came on the engine in third and above it seemed to run into a 'dead' patch above 2,500 rpm. I could rev it through to 4,000 and I could achieve 70 mph but overtaking was a bit scary. Also I had the feeling that if I lifted off ever so slightly, it seemed to go better.

    I looked up the specs for that engine and it quoted a 0-60 of 12 seconds and the very best I could do was 16 seconds which is a lot slower. I wondered that maybe as I was somewhat obsessed with getting the best mpg I could, maybe it had got all carboned up and really all it needed was a good blast so I spent a tankful revving the nuts off it. No improvement. Now I'm not a believer in bottled cures but I did some research and Archoil AR6400-D seemed to have good results so I invested in an (expensive) bottle. I also changed the fuel filter at the same time with a splash of Archoil directly into the filter. With bated breath I used the bottle over two tank's worth. I think I felt an improvement but actually I think it was just wishful thinking, certainly there was no improvement in the MPG which continued its downward slide and the black hole, as I now called it, was still there.

    I was now starting to question my own memory of how I thought the car was before all this happened because it was very gradual. I use a very steep hill on my way to work and this Golf was really struggling to get up it whereas I was pretty sure it used to breeze up it. Certainly my old A4 with the same engine (as good as) used to accelarate up it. In the end, after a lot of logical deduction I knew it wasn't the turbo, it spun freely and there was plenty of boost. I could not believe it was fuel even though it really did feel like there was a restriction of some sort. The fact is that the fuel system runs in brand new, micro-filtered lubricating oil all the time so why would a moving part get sticky or stop working, I put a new filter on and I knew the injection timing was spot-on (checked with VAG-COM). The injector cleaner didn't really do anything. It was time to face the inevitable, the Mk4 seems to have a reputation of faulty MAFM so I decided I'd buy a new one. I looked around and bought a replacement (NOT Bosch) meter and fitted it. It did feel better again but still, in the weeks that followed I still felt it wasn't right and it was still a struggle to get up that hill every evening.

    I was still plunging around on the internet seeking inspiration and more than once I read "please don't buy a cheap MAFM, buy the proper Bosch one". OK, I decided that my logic was leading me to my second inevitable decision, I was gong to HAVE to buy a Bosch meter and the cheapest on eBay was £94 flippin' quid! I closed my eyes and clicked "buy". It took all week to arrive but the morning it did, the good old postie arrived before I left so I bunged it on there and then. Nervously I set off, I could not belive it was going to fix everything but logically, that was all that was left. Well, to cut a long story short, my performance was back! It now went like a little car with a big engine and I had all my overtaking oomph back! OK, the moral? You can buy replacement parts for some things but you really can't beat genuine parts and sometimes ONLY those will do!

    If you've read right to the end - congrats!

    Cheers VeeDubbers!
     
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  5. Re: Golf 1.9 Tdi Unexplained loss of power 
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    Actually we nag people to buy genuine VW Air Mass Meters, not Bosch as there are a lot of counterfeit Bosch AMM's around on fleaBay and they are not a great deal more expensive.
    Anthropogenic climate change, the biggest con inflicted on mankind since religion...

    Slava Ukraini
    !


     
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  6. Re: Golf 1.9 Tdi Unexplained loss of power 
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    Agree with the comments on the AGR engine; I've owned 2 Golfs with that engine and the only problem I had in a combined 150,000 miles of motoring was an air mass meter failure. Fortunately a colleague at work had the same problem a couple of months before me and diagnosis was easy between us. Unfortunately it happened about 4 days before a 3 week trip to Norway and I had a nervy run around getting hold of the right part. I followed advice from the forum and got the part from a VW dealership; it was an easy fit and I had a trouble free holiday and no other breakdowns with the car.
     
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