Engine: TDI: Slow return to idle

[slimeslab]

Hi,
Thanks for the replies.

Re crank position sensor.
I have done a quick google and can seem to buy one for a P1 car up to 2000 and then for a D5 from 2002 on but not for a audi engined P2 2000-2002

I'll check vida. Could be a quick fix maybe.

The sticky injector...apart from pulling them and getting these tested is there a way to prove/disprove this idea?

Thanks

Martyn.

[slimeslab]

Quick Update on this -

I have done some testing and live data readings in Vida -

Here is a youtube clip of the engine speed sensor 1 & secondary engine speed sensor (needle lift injector) whilst revving the engine.

http://youtu.be/yQPDIj6U2HI

Also - I tested the resistance of the needle life sensor and it was 106ohm - vida says a value of 95 is correct.

So...is my no4 injector (needle lift sensor) knackered?

[Chris_Rogers]

The needle lift sensor works by generating an electrical impulse from the needle movement caused by fuel being injected, when you lift off the throttle pedal there would be little or no fuel so the needle lift sensor probably won't operate.

The resistance reading is at a certian temperature, usually 20°C and there will be tolerance, did you measure at this temperature, how accurate is the meter you used?
I'd suggest your needle lift sensor is fine.

[slimeslab]

Hi,
Thanks for the reply.
The multimeter was a good one. So the reading was accurate.
As for temp..well I didn't have a thermometer but it's was yesterday morning so ambient was probably not far off 20.
I'll check it again this morning with a thermometer nearby to be sure.

The dips in the secondary engine speed live data graph when the weird idle return happens are the only bit of "data" that is out of place.
The throttle pedal sensor is a nice smooth graph on both analog and digital.
So I'm running outta ideas...where to test next.

I'm guessing no one else's v70 tdi p2 does this then?

Cheers
Martyn.

[Rossey]

Mine does it.

I was hoping you'll tell me how to fix it lol

[slimeslab]

Ah ha - a fellow sufferer

What have you done to diagnose yours?

Does it do exactly the same thing?

[Rossey]

I've done nothing, I'm new to volvo.

I noticed it when driving then I saw your thread.

It does exactly the same thing, I don't have the software to check it out.

[Adel2789]

Originally Posted by slimeslab

I will certainly try giving it the beans and clearing out some black sooty crud.

I took a video of the slow return to idle.

Seems more prevalent when the engine has warmed up.

And it's the last 1000revs back to idle that are the issue.

http://youtu.be/UwsoF9ptMgc

Thanks

Martyn.

Hello any solutions for this problem ?
I have the same problem

[brickman]

Originally Posted by Adel2789

Hello any solutions for this problem ?
I have the same problem

Its likely nothing to do with that area of the system. Instead check your 'injection quantity' in VOL/fcr or VIDA when engine fully warm and sitting at idle. Should be about 4.0 to 4.5 units. Martin made a great post about this 5 years ago (search for it) and helped me sort mine out. If the number is lower than that amount basically pump is injecting slightly too much fuel at a given RPM/at idle, if the number is higher its actually putting in less fuel vs the amount the pump THINKS its putting in.

In VW/VAG TDI land its called 'SDS' or 'Slow down shudder'. It happens when engine is on overrun cycle either in gear or in neutral/coasting, no throttle is applied, brakes are applied and the vehicle speed is > 0mph. As soon as you actually brake to a stop, it will begin idling normally again.

Look up 'hammer mod' on TDI forums (VW based, but same bosch VE system), thats how you 'nudge' your electronic sensor head in the pump to the correct position (4.0 to 4.5 units). If it reads lower than that you'll likely have constant low amount of smoke right across rev range, but also more power. If it reads higher than that, you might have starting issues (won't start when warm without some throttle input), but your MPG will read higher than normal (but you likely won't actually get better MPG) and car will have less 'urgency' to it at lower rpm range, just feel a bit lethargic.

Don't try to loosen or undo the weird bosch 3 sided bolt, leave it where it is.