Club 80-90 Forums

So my Syncro Doka (DJ engine, 2.1) has been giving me some headache this last week. It won't idle when cold. If i give it some gas no problem at all, also idles perfectly when hot. A bit tired of having to use the left foot for braking during warm-up.

- Checked the throttle position switch which needed adjusting (no click on "idle"). Adjusted and checked with multimeter and seems fine now, doesn't click on full throttle though but I'm not too bothered with that at the moment. I was pretty convinced this was the problem at first but adjusting did no difference at all
- Checked the Temp2, no problem but changed with a known good one just to make sure.
- Checked the Idle stabilization valve / aux air regulator. Seems fine on the bench. However doesn't seem to be getting any voltage (or very small amount, ~2V) when cold.
So I'm suspecting this is the culprit, but what's next? It's a bit hard to test when idling as it doesn't idle on cold, but I assume it should be getting full power with accelerator pressed down as well as long as the engine is cold, correct?
Tried to check the idle control unit/relay/thingy behind the right hand side tail light, but not really sure how to test it. Wires from the valve to the relay seems fine. Should I get a new unit/relay/thingy or is there something else that should be checked first?

I also tried bypassing the idle stabilization unit next to the coil, no difference, and cleaned up the earth points, no difference.
I've had this problem intermittently before but but it disappeared until now...

Any help or hints would be appreciated

Well, I tried another idle control module. No difference. No vibrations from the valve. Still no idle until hot.
Any digijet experts around? What am I missing?

when you say the valve tests ok on the bench what do you mean ?

Checked resistance on the valve (4ohm, which would be within spec). Also took it out and applied 12v to make sure it opened up when cold.

I don't know your engine set up but this may help. I had a similar problem with my old bay a few years ago. It turned out to be a break in the wire connected from the solex carb to the fuel cut off switch. It was fine going along at speed but as soon as I slowed down I had to use handbrake to stop while revving the engine. A nightmare. I joined the wire up again and hey presto the switch remained open. I hope that this helps. Good luck.

Patrick

If you don't already have it, try Googling 'VW Digijet Training Manual'
I'm currently working through it as I have starting/ idling problems
Laid out in a logical way and quite easy to follow IMO.
I reckon that our old vans will have developed other wierder problems by now but worth at least starting by the book.
Hope it helps.

skippymoss wrote:If you don't already have it, try Googling 'VW Digijet Training Manual'

The link to the pdf document comes up in second place on the page but it says "Password Protected File". I'm on a PAYG mobile dongle and since the file is 23 MB I'd rather not waste my credit downloading a file that I can't open so my question is.........

do you know the password?

No password here;
http://www.mediafire.com/?uuv57dpoq4d86np
Just download and open for me

Thanks for the tips skippymoss and Patrick. Actually already found the manual, and also have a similar manual in Swedish covering the digijet systems. Both are very helpful indeed explaining how stuff is supposed to work and how to do the checks, however there is some parts in the Digijet training manual that differs from the europe spec late 2.1 DJ engines.
If anyone have troubles with downloading it send me a PM.

Will start going through the connections on the idle unit tomorrow making sure it gets the signals and power needed etc.

skippymoss wrote:No password here;
http://www.mediafire.com/?uuv57dpoq4d86np
Just download and open for me

Ta muchly

Well, went through all the necessary connections on the idle unit, rpm, temp, tps etc just to find no problems.
So I thought I'd give the aux air regulator another last try before handing it over to the workshop. Had another valve in box of spares and popped it in and hey presto, it idles
Tried the old one again on the bench. Opens up no problem when applying 12V but not in the car apparently, don't really get that. A bit daft not to have tried the other valve immediately but hey ho. At least I got to learn a bit more about the digijet idle system.

Thanks for the help anyway.

Glad to hear you've cracked it - so there's hope for the rest of us!
Just one thing - when you say you "went through all the connections", what exactly did you do to test them?
It's what I'll be doing tomorrow...

I used the wiring diagram in the Haynes manual. The colors of the wires didn't match but was able to figure out most of them. Used a mulimeter and just tracked the wires to the different components (or to the correct pin on the ECU plug) and made sure there was continuity were it should. You can check the Temp2 and TPS directly at the ICU socket using the same methods from when checking them directly at the component or at the ECU plug. I checked the RPM signal at the green wire from the coil. Hope that makes any sense

Another note if anyone finds this thread in the future. As said I measured a low voltage (~2V) at the plug to the aux air regulator when the engine was running. This would actually be correct as the signal to the valve is a on/off wave type of signal and the multimeter will show the average voltage. If you get any voltage at all the valve should be functioning, and the wires between valve and ICU should be ok from what I can gather. I'm no expert though, obviously!

Sebastian.

Could you point me to the Swedish Digijet manual, please? (Don't worry - Swedish is no problem for Ellie...)