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Revving problem AFN, ???

Discussion in 'A4/S4 forum(B5 Chassis)' started by scr8pdo, Jan 27, 2013.

  1. scr8pdo
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    scr8pdo Member

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    I have a bit of a problem but til now I have put it down to maybe the inlet or turbo clogged or caked, it still maybe the problem as I still havent cleaned the inlet out as we have arctic conditions at the moment here lol but I will list the symptoms/problems below and it may sound familiar to some of you:

    Basically the car seems to pull well up to around 3k rpm but after that it feels restricted, especially on say a motorway, as I say I thought this maybe due to a restriction in the manifold, but another problem is if I rev the car from idle up to a certain point the engine will hesitate, puff a cloud of black smoke out and vibrate, if I remove my foot the engine will normally shudder a bit then regain its composure so to speak, but the other day when I did this, the engine cut out, I tried to restart it and it almost sounded as if it had no compression except on say one cylinder, then the oil pressure light came on (still engine spinning not firing) I started to worry I had done some serious damage at this point, but then after turning for a few more seconds, the light went out and the car started as normal????

    It was as if the valves had been stuck open for a few moments resulting in lack of compression hence the cut out and the starting problem....weird?

    Does anyone have any ideas, or could it be a result of a carbonned up inlet and over fueling/rich etc or a possible problem with hydraulic lifters over pressurising holding valves open, the car runs fine around town, and only becomes a problem on a run when exceeding 3k rpm ish or when revved a bit too hard when idling.

    I will get around to giving it a good service as soon as the weather permits, I have all the filters, oil etc and going to do the EGR delete plus clean the inlet if need be, any help would be great, kind regards Steve :)

    PS: the car has a few minor mods:

    Decat, tuning box, cone filter, it looks to have brand new vac lines everywhere, dont know if there should be anything else to look out for????
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  2. adamss24
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    adamss24 Well-Known Member

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    Most likely injector pump on last legs, do a scan and see if any faults logged in !
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  3. scr8pdo
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    scr8pdo Member

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    Thanks for the quick reply, I was going to do so but was told that it wasnt OBD, its not a PD, I dont know if this makes a difference?

    Its the early type I/P, if this is a problem (with the pump) would it show up, the car is a 1997 BTW
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  4. TeKnodriver
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    TeKnodriver Biodiesel Purrrr

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    hopefully just seriously clogged fuel filter, or even IP timing slightly out.
    Do filters first and see if any improvement
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  5. MaverickTDi
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    MaverickTDi Member

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    I've had very similar symptoms. If I accelerate hard beyond 3-3.5k you feel the engine back off and there's no get up and go what so ever. I have to turn the car off and back on again and the fault disappears, boosting fine. Today, I put some cataclean in the tank, so we'll see if that helps the situation?

    I haven't owned the car for long, so I doubt the turbo/inlet manifold have been cleaned. I bought a spare replacement turbo the other week off eBay, so I plan to change it and give the original one a bloody good clean and rotate the turbo's every 30k or so.

    It is a very strange fault as driving normally is fine but under enthusiastic driving it seems to feel restricted and almost stalls. I did think it was the turbo actuator but might try the above and see what that does.
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  6. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Maverick: That sounds more like sticking VNT causing an overboost condition. The fact it only fixes itself after you cycle the ignition is indicative of the ECU dropping into Limp Mode.
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  7. ScottD3
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    ScottD3 I want your faulty electronics

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    VNT vains.
    Same problem as me.
    Check my Lost boost post. :(

    I've decided to drive the car with out reving over 3k.
    Which is really hard in a auto lol
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  8. adamss24
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    adamss24 Well-Known Member

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    Could also be the case pressure valve coming adrift, seen a few with that problem...As Kev said above, do a scan first and make a note of the fault codes then post them here...
    Had a pd130 passat with an overboost problem this weekend for a cambelt, after working the VNT mechanism on turbo up and down + letting the computer cycle the N75 valve on and off (to move VNT lever) the car did not drop in limp mode at all. However, in your case the turbo should not clog if it gets used properly but larger nozzles and slow driving might cause sticky vanes on the turbo...
    Also your engine is a VE type with a VP37 rotary pump, the best engine VAG group ever made...
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  9. scr8pdo
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    scr8pdo Member

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    Thanks for the advice guys, it sounds like a pretty common fault then, and yeah it does seem to go into limp mode if I acce;lerate a bit too hard, it will feel gutless until I turn ignition off then back on, I will get round to giving it a bit of attention as soon as the weather permits :)
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