Audi 80 tdi juddering bucking jerking

[Obsidian]

cheers guys! hey Allan! where is this ECM thing and how do i get to it, your fix sounds liek one i'd liek to try myself, i do alot of miles daily, i can't tell you how it drives me nutty this shudder. I've not been able to locate a wiring diagram for my TDI, no manuals for them anywhere, so i've no idea where or what relay 109 is ini, but that really does sound worth a look at, any1 got a wiring diagram, i'm an electrician, i understand these things!

[avanttdi]

hey alan! let me know how you get on with scoping the signal, i was going to do this but never got round to it.

i am 90% sure that the clocks convert the signal from the analogue sine wave produced by the VSS into a digital (square wave) format that the ecu can understand.

please could you draw me a little picture or describe where pin 49 is on the ecu plug? i have been driving about with the speed sensor unplugged for ages, but i have to do a 500 mile trip soon, and so i desperately need the speedo working.

i can live with the rough idle, and i can take the flashing bulb out for the time being. btw what is CEL i have never come across this abbreviation.

please keep us all posted on your progress. dont find the fix, and then forget about us all!

many thanks

[avanttdi]

update as promised. today i tried unplugging my crank sensor ( for reasons/suspicions explained previously)

i would like everyone to know that it made no difference, so from this i have concluded that we are not dealing with an implausable or noisy crank signal.

the engine ran exactly the same using the needle lift sensor as a substitute function.

one more thing eliminated.....

[STiVO]

This problem has had me stumped for months, but the VSS (Speed sensor) leads have really helped.

I have had shudder at idle but this can be tweaked with VAG-COM TDi timing checker and/or physical pump timing.

The main problem has been the quite bad jerk/shudder at low loads which will only dissappear when breaking the drive (clutch) or powering through. I've tried everything to stop this, engine mounts, MAF, N75 Valve, Cleaning Inlet Manifold, blanked off EGR, altered timing (physical and software) with no effect on this problem what so ever!

I finally got round to removing the dash fuse, then bingo all fine! Apart from obviously no dash. If you remove pin 43 from the ECM you get the same result, except you have the CEL flashing, I assume because loss of speed signal, but the speedo works ok. Pin 43 goes to pin 18 (on the blue dash connector behind dash), I assume the speed sensor feeds the dash which conditions the signal for pin 43 of the ECM.

My next step is to scope the signal, I have two wires hanging down behind the glove box at the moment so I can dis/re connect the wires when I need to, and also connect a scope.

Now, what does the dash do with the speed signal, I don't know yet, but I wonder if its a problem with the dash or whether we have some control loop problem as the cars are getting older. I've read that the ECM monitors vehicle speed to determine acceleration or deceleration.

It drives beautifully with pin 43 disconnected and you have all the dash functions, even the speedo working, I've removed the CEL bulb, while I'm investigating, but I'm determined to find the problem.

Anybody else have any more info??

Hey Allan, I joined the forum just now to reply to your post.
I have a similar problem, juddery/lumpy tickover (but sometimes fine) then the judder sometimes while accelerating and sometimes while cruising. Strangely it can run fine occasionally!
Also yesterday for the first time there was a lack of power (just once) until the revs were up a bit then the power kicked in.
I'm wondering whether to try your pin 43 trick, could you please provide some 'instructions for dummies'? And which bulb is the CEL one?
Thanks for sharing the results of your determined efforts to rectify a problem that distracts from an otherwise superb automobile!!

I almost 'upgraded' to a 1997 tdi Passat estate but after reading about all the electrical faults caused by rainwater in the ecu, and what with catalysers and so on I thought I'd stick with the trusty Audi! Anglesey and back (430 miles) on 38 litres can't be bad for a £900 motor!!

CHeers, Steve

[allan_audi]

VSS Vehicle Speed Sensor - Jerking/Juddering

Great to see all the interest! Bare in mind my car is 80 Avant 1994 1Z TDi, not sure if it applies to all, so please check first.

You can either remove pin 43 (White/Blue wire) on the ECM (which is located behind the glovebox, behind the heater fan). I found the pic/pinouts here;

http://www.hasenwerk.ca/tech/wiring/earlypassat1z.pdf

But it would be easier to cut the wire from the dash, I found that it goes to pin 18 (White/Blue) on the blue connector at the rear of the dash. You will find the markings for pin numbers on the socket of the dash, just count along to 18, then check the colour, cut the wire (insulate, just in case). To remove the dash remove the cowl (two screws underneath), then the two screws for the dash. You don't need to remove the steering wheel (disconnect battery if your unlucky enough to have airbag).

The CEL bulb is the one for the glowplugs, the orange lamp bottom left (then up one, I think!) to check just turn on ignition look for glowplug lamp, remove that one (its a bulb with blue holder).

I'm gonna try get round to scoping the signal! I did think that it might be converted to square wave here, so there is slight chance of fault in the dash VSS signal. I'm more wondering whether this is a closed loop fault, ie play in gearbox, not sure what the speed sensor picks up off, crown gear, dont know?? Maybe theres play in the gear that feeds the VSS. I know the gearbox on mine is fine but there's a fair amount of backlash in the drive train.

Whilst I'm here, there are other faults that people are discussing on this thread, I don't think they're connected to this cyclic jerking/juddering problem.

Loss of power seems to be a problem with EGR, MAF or boost. For instance one of the boost pipes had come loose on mine, I'd already blanked the EGR valve off, I tested the MAF using VAGCOM and seemed fine, then noticed a boost pipe was loose. I have heard of boost pipes splitting. I guess the best way would be to connect a boost gauge.

Incidentally I fitted pair of SJK Digital tuning chips, the difference is awesome, around 115BHP I think, the torque increase is excellent and doesn't seem to have affected economy much. Well worth the 60 odd quid, just need to remove the ECM and dismantle to fit. Its funny watchin some of the other cars try and get past up the hills!!

Anyhow, going on again, got so much info on this car, I'd almost given up with the VSS problem, but the cars so good to drive!! Plenty of life in her yet!!

Keep up with the info everyone!!

[allan_audi]

PS.

CEL - Check Engine Lamp, flashing (during engine running) indicates engine system fault, or at keyon indicates activation of glow plugs (plus lamp check, ie. CEL lamp bulb not blown).

I'm also not sure about 109 relay (this maybe a VW thing, I don't know if its same for Audi 80), this is the relay that powers up the ECM, I haven't changed it yet, but its possible this could cause intermittant problems, ie engine cutting out, but I think this would be at all operating conditions. Suggest anyone wth misfire etc tries this one out, let us all know!

I don't think its connected to the VSS problem.

PPS.

I've had not luck with help from Audi so far, they're not interested, its so frustrating not to have a wiring diagram for this car!!

[allan_audi]

QUOTE>>

lo there ini, thnx for the interest btw, sorry buti can't post vagcom stuff, not sure what that means so have no idea where to get the readings you require. Yes, fuel injectors where cleaned recently, by a deisel specialist used by Audi Lincoln. Not convinced of his efficacy since he broke my accelerator pedal and cable-tied it back together and blocked the EGR valve vac feed with a ball bearing, for what purpose the almighty knows.

Needless to say i'm now going to try and fix this myself, the clutch is a new one and there's no loose bolts or mounts.

NOTE: don't bother with the throttle potentiometer, i removed mine and disconnected it, there's a six pin plug near to it that feeds it. the idle speed increases to factory default emergency throttle, but the hunting still continued! it ain't the throttle gadget!
<<


Funny, the ball bearing is to stop the EGR valve opening (assuming its already closed when you stuff the ball bearing into the pipe), bit crude, especially seince they mostly fail stuck open (physically). Best idea is to make a blanking plate for the EGR valve itself out of some plate steel, so even if the valve opens exhaust gases cannot reach the inlet. EGR valve is known to cause problems, inlet clogging with black oily crud, plus sticking open etc, loss of power/boost. Its not really needed, its only there to reduce NOX emissions.

I'm fairly certain that the clutch has nothing to do with the jerking juddering.

I was also convinced that the throttle pot plays no part in the jerking, since it would cause problems on and off load. ie. you would be able to get the car to jerk in neutral by adjusting the throttle.

[Obsidian]

that's interesting you should pick up on that allan, i've looked at the egr valve before, took it off but i can't seem to get any movement in it, i just assumed it need quite some force, but maybe not! Worthy of another look. I also, whilst at that valave, took my pipework off to look further and found there was considerable crude in the inlet manifold. I'm assuming that's what it is anyway, it's a silvery box along side the engine, seems to be quite full of oily crude. is this what you mean by faulty egr symptons?

thnx for the pdf, interesting read that.

still strugglingto find this 109 relay!

[allan_audi]

that's interesting you should pick up on that allan, i've looked at the egr valve before, took it off but i can't seem to get any movement in it, i just assumed it need quite some force, but maybe not! Worthy of another look. I also, whilst at that valave, took my pipework off to look further and found there was considerable crude in the inlet manifold. I'm assuming that's what it is anyway, it's a silvery box along side the engine, seems to be quite full of oily crude. is this what you mean by faulty egr symptons?

thnx for the pdf, interesting read that.

still strugglingto find this 109 relay!

Just to point out EGR fault doesn't cause the VSS problem we're discussing.

Look at the TIDCLUB page for info on EGR, I took my manifold off to clean a few months ago, absolutely caked in crud and can affect performance if severe. The EGR recirculates exhaust gases which mix with the oil from the breather and turbo to coat the inlet manifold. So I cleaned the manifold and blanked the EGR, should remain clean now.

http://tdiclub.com/TDIFAQ/TDiFAQ-7.html#g


There's mention of the 109 relay on the TDICLUB too, I'm guessing its in relay box under bonnet or could be one of the relays under drivers side dash. Anybody know???

[ini]

This is for an A4, but the relay is most likely in the same location.

http://forums.tdiclub.com/showthread.php?p=300195