TDI90: occassional wobles, shaking, vibrates at idle

I was wondering if it is the oil pump chain/crankshaft balancer, but why can the engine run fine sometimes and sometimes not?

Page 1-3 here is about worn chain tensioner causing the crankshaft to get unbalanced
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[ATL, Motor] Starke Vibrationen beim ATL – Pumpe-Düse oder doch nicht?

So. Am Samstag ist auf der Fahrt nach München ein Zylinder ausgefallen. Das Auto fühlt sich in diesem Fall sehr seltsam an: Es rumpelt und schüttelt fürchterlich im unteren Drehzahlbereich, Leistung ist deutlich weg, aber wenn man schneller fährt, merkt man fast gar nichts mehr. Keine Warnleuchte...
a2-freun.de
 
Intermittent problem, I still like the idea of faulty injector loom, especially as it sometimes does it on idle.
 
Yes intermittent problem yes.

Should faulty wiring loom be evident when monitoring the injectors fuel trim in VCDS?
 
That shake does look like misfire or incorrect fuel burn. Faulty loom hardly ever shows up on a scan.
 
AndyP said:
Only if it happens to have failed at the time you are checking it.
Click to expand...
Actually, upon reflection, as you are connecting to the ecu and the ecu thinks it's sending the correct signal to the injectors, I'm not even sure it would show up if you scanned while the engine was misfiring ...
 
My old tdi 75 about 4 years ago had the same sort of issue, ran fine and sometimes engine vibrating like it was going to fall out.
I discounted the loom as sometimes it was fine, until someone told me to check it. some cracked wiring, so changed the loom and it was sorted, never had the issue again.
 
Hmmm... sometimes when cold on idle, I can press the clutchpedal and the shaking fades away. Releasing the clutch pedal again, shaking reoccurs.

But only happens sometimes, and typically not after being idling for 20 minutes. Sometimes I can also drive for 2 hours before the shaking starts.

I really do not get it.. some resonance issue with DMF??
 
It seemed to be rather odd in my case, i am still convinced a bearing is going either gearbox or motor side holding either end of the shaft, but on the long weekend I've taken most of the intake off gave it a clean (didn't get to EGR yet) and cleaner airflow sensor, it runs smoother and wobble is gone almost completely... There was quite a lot of oil making into intake from breather tube it seems so i'll pop an oil catch can in there somewhere to see how it does with it and if further detective work is required - the tubing all the way through intercooler up to EGR had a noticeable amount of oil settled and breather tube was a small river, can't be too bad getting rid of what seems to be very excessive amount of oil there.

Might be worth a shot as easy enough to do?
 
Olerype said:
My car is behaving strangely. It can drive just fine, but after a while it can start shaking when accelerating or going up a climb. Really strong and disturbing shaking. Normally just in 4 and 5th gear between 2 and 3 rpm. Disappears if going of the accelarator or de-engage clutch.

The strange thing is, that it does not behave like this always, and it can also go away just by stopping. Travelling on the autobahn in 75mph, the shaking starts after 1 hour, I de-engaged the cruise-control and pull over for 5 minutes. Then I reenter autobahn, accelerates just fine, and enable cruise control again at 75. Shaking disappeared.

Not mapped, new struts and top-mounts, new wishbones, wheel-alignment done.

Drive-shafts, diesel injectors, engine mounts, turbo variable vanes sticky? The dual mass flywheel appears fine; no noises at all. Engine pulls fine. Idle is also fine. No noise from oil chain.

Was thinking driveshafts/CV joints, but just strange that it can disappears for a while just by stopping for a short while?
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I had heavy vibrations in my car 1,4tdi after replacing the wishbones. It was worst between 70-100km/h. The problem was that I got wrong parts, I got wishbones and bushings for an petrol car. After changing the wishbones to the ones for a diesel the problem disappeared.
 
gagge said:
I had heavy vibrations in my car 1,4tdi after replacing the wishbones. It was worst between 70-100km/h. The problem was that I got wrong parts, I got wishbones and bushings for an petrol car. After changing the wishbones to the ones for a diesel the problem disappeared.
Click to expand...

The car vibrates at standstill/idle
 
The flywheel rotates when the engine is running. Depressing the clutch does not stop the flywheel. I still think it is a injection issue and probably the injector loom. A bad earth or at least intermittent could also cause the "misfire", to rule this out run a temporary second earth between the block and chassis. If this improves the matter fit a permanent second earth. If no improvement then still say it is the loom.
 
@audifan I was moving the car just now. At standstill idling; when clutchpedal is pressed (in), the shaking fades away after a 3-4 seconds and the engine runs ok. When clutchpedal is out (depressed) the shaking starts. How can the injector loom be affected by the clutchpedal position?

However, sometimes expecially after some time on idle getting warm, the engine can run ok also with clutchpedal out (depressed).

Are you 100% sure that the DMF spins regardless position of clutchpedal?

Is the ECU reading the position of clutchpedal and alter the fuel injection or similar?

The clutch is otherwise ok with respect to drive off from standstill in 1st gear etc.

The car is also ok cruising on flat roads/highways. The shaking starts going uphill while maintaining speed (ie when more gas is given)
 
Injector loom can not be affected by clutch . The video looks very much like a misfire shake. So I am now torn between loom and DMF / release bearing / shaft. Certainly one of the flywheels has to turn as it is bolted to the crankshaft. The second connected to the transmission via the clutch can rotate independently of the first. The loom is cheaper but now not sure it covers all the symptoms you have. The DMF more expensive and more work to replace. DMF failure is relatively common in other VAG models. To make things worse neither the clutch nor the loom will trigger warning codes. Take a look at this video it may explain more about DMF

 
If the car is in gear, releasing or dipping the clutch causes a torque reaction from the engine as it tries to rotate on the mounts. It's only a theory but the movement may pull on the external part of the injector loom and open up any breaks in the wires.

Cheers Spike
 
Just had a short trip to the supermarket.

1st start since yesterday: clutch pressed, starts rough as the engine «max» the engine mounts, some tendency to shake even with clutch pressed. The shaking gradually picks up and gets significant worse if depressing the clutchpedal, and correspondingly fades away if pressing the clutchpedal again.

5 minutes drive i 1,2,3st gear to market.

2st start: clutch pressed, smooth start, and smooth running. Depressing the clutchpedal and shaking gradually picks up. Fades away when pressing the clutchpedal again

3st start: same as 2st start but now the car idle fairly smooth for 5 minutes also with clutchpedal depressed

The gearstick is in neutral in all above starts.

The car drives fine except some juddering when accelerating in 1 and 2st gear.

Could make sense that misfiring cause some resonance effect with DMF?

Edit: forgot to say; there is a small humming when clutchpedal is depressed, but would not judge this humming to be alarming. Just a change in sound from enginebay basically
 
Although this probably will not make much difference in this case, it is worth while doing a brake and clutch flush and refill, chances are it is overdue anyway. Brakes and clutch fed from same reservoir.
 
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