G80 Implausible Signal (AEL)

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Hi all,
this forum looks great! There are a lot of useful and interesting information about VW engine, that's what I'm searching for.
I'm italian and I don't speak german, so I try to explain my problem in english.

I've an Audi A6 TDI 2500cc (1995 - AEL) but the engine doesn't work well: it sometimes makes little "jumps" ("sussulti" in italian) or a sequence of them at all conditions or rpm. They makes my car undriveable
The ECU (using vag-com) reports:

Quote:

00542 - Needle lift Sensor (G80) 27-10 - Implausible Signal - Intermittent

I checked G80 cable, cleaned N108, checked for air bubble in the fuel system... but nothing has changed

So I've connected a little switch and with it I can disconnect G80 (from the compartment) when the engine starts "jump", in practice I force the emergency program. When I exclude the G80, in fact, the start stop jumps (the performance are naturally poor) but at idle speed sometime the engine still "losts" some strokes.

Please help me guys, I'm losting my drive-passion!

Thanks in advance,
Laurento

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Hi Laurento,

do you know the "needle lift sensor" check ?

Start the engine and let it idle (hopefully it does it without selfmade "sussulti").
EDIT: not idle, but 3000 rpm

Then take a screwdrive or hammer shaft and hit the sensor-nozzle with the shaft.
If the sensor itself is damaged, you should be able to force the "sussulti" with these hits.
This means you will have to exchange the nozzle.

I'm a little bit confused about that:
The "sussulti" without a connected G80. This stands in contradiction to a broken G80.

Greetz
m;

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Hi Laurento,

you need to check the needle lift sensor itself. Measure the resistance at the connector and post the value.
You may also do the following check: let someone hold the engine rpm at ~3000/min, then take a skrewdriver and hit on the needle lift sensor; the needle lift sensor is inside the nozzle holder with the cable.
If the engine interrupts, you will need a new nozzle holder with needle lift sensor (because it is one part).
Check also the connection cable of the sensor and the connection plugs.

Best regards, Rainer

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dieselmartin wrote:

'm a little bit confused about that: The "sussulti" without a connected G80. This stands in contradiction to a broken G80.

I'm confusing about it too

Thanks for the fast responses

I measured the resistence of the G80 (some months ago) and it's in range (i don't remember exacly about 98-100 ohm I think) but I'll re-misure it and I'll post here to be sure.

I'll try the "skrewdriver" test this weekend... I'm not at home at the moment.

Many many thanks for the interest, I'll post the results of the misure and of the test this weekend.

Meanwhile I read your wonderful scientific papers

Cheers,
Laurento

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The resistence when the engine is warm (about 90C) is equal to 119 ohm (I remember that when it's cold the resistence is about 98-100 ohm)

I tryed hitting the G80 but nothing happens

I also remebered that when the engine makes "jumps" the ignition timing reported by vag-com raise for a while to 255 (data block 000)