2.1 dj over revving at idle

[mart 475]

hi any help with this would be greatly appreciated.when i start my bus it idles at 800ish rpm but after a short distance this becomes 2000rpm.if i revved heavily it would drop back down to 1200rpm but recently the heavy rev tactic aint been working and its sticking at 2000rpm, it does drop for a split second but the rev counter bounces straight back up to 2000rpm.my bus is a 1987 club joker 2.1 petrol.this is probably a coincidence but i replaced the coil yesterday and yesterday was the day of the 2000rpm syndrome beginning and its the same today. prior to that the bus hadnt moved for a week. thanks for looking mart

[Ian Hulley]

Swap the coil back and see what that does. Why did you swap the coil ?

Ian

[mart 475]

hi ian i swapped the coil as i had no spark occasionally but would start once the coil cooled down.to be honest the problem started weeks ago but as i said a good hard rev on the pedal would then decrease the revs but if left it would start creeping back up til revved again.its just the last two days its been sticking at 2000rpm when revved the counter decreases but instantly bounces back to 2000rpm. thanks mart

[Fritz]

This ringed item controls idle speed,if it is working properly it will buzz rather loudly when engine is running,,,,,,, what is your doing at any given time ?

You are going to have to check it by listening to it before and after start up to the point of the high revs situation,,,,,,preferably by standing over the engine while a mate does the important bit at the front...



Regards


Fritz,,,,,,,,,

[mart 475]

thanks fritz i'll do that tomorrow.mart

[mart 475]

hi fritz,i checked the item ringed in your pic and it aint making a sound,if however i stand at the rear o/s vent i can hear buzzing but nowt from the unit itself.the bus runs great for 10 mins at 800rpm idle and then kicks off,so to speak,at 2000. do you think the unit is knackered and if so any ideas where i could get one and is it just a straight forward swap over?(too many questions in one sentence!) also what is the part called ? thanks for your help mart

[HarryMann]

Try cleaning it out with carb cleaner - a good old squirt both ways..

Follow all the wring to it, check and remake the connections, look for signs of damp ingress and corrosion in the connections both sides..

Remake the T2 sender connection on the thermostat, check the wiring for breaks, when its idling fast, move the T2 sender wiring about. Check the connections on the AFM and take a look behind the o/s tailight, which compartment contains the unit that controls that Idle Stabiliser Device.. If its soaking wet in there then dry it out and clean/remake the connections.

Read the Wiki thoroughly here:

https://club8090.co.uk/wiki/Pe ... ittent_2.1

and take action if any of the symptons seem to apply, or any of the actions make sense e.g. poor, damp or corroded connections.

[HarryMann]

.. and take note if any one else responds with specific 2.1 DJ symptons that you can relate to.

[mart 475]

hi harry thanks very much for your advice.will do this and let you know how i get on. thanks mart

[mart 475]

today i checked all connections which appeared sound with the bus idling at 2000rpm then i cracked on,when i replaced the coil last week a yellow block,which appeared to come out of the two pin side of the coil,was disconnected. i thought that i must have knocked it so i re connected it and thought no more.today,however,with the bus idling fast i disconnected said block and hey presto immediate reduction in revs to 800rpm.i know this is probably good and bad! good cos it solved my 1st problem but bad cos it means that summit else is up! any thoughts and help you good people have would be greatly appreciated. mart

[sonic23]

Aha - I too have the same problem at the moment and I believe i've isolated it to being a faulty Idle Stablization Control Unit (ISCU). (Note - I've re-adjused the TrottleValve and made sure the micro switch is functioning as per Bentley)

Unless I'm really mistaken, that little Yellow connector that you joined together is from terminal 1 on the coil to terminal 17 on the ISCU. Here's a little test - remake this connection. (Revs go back up). Now go the ISV itself, and unplug the connector. Do the revs drop again? If they do - it means the ISV is working, but the ISCU is not.

If you unplugged it and the revs didn't drop - it would mean that the ISV is probably stuck open (Carb cleaner time).

Well....that's my pennys worth....i'm sure someone will be along to correct me.
I'm getting a replacement ISCU from CJ at Syncrospares - so will report back on my findings....

cheers,
Rich

BTW, there's lots of info on this on thesamba.com. A guy called tencentlife seems to be the guru. (Search on ISV and ISCU within the vanagon/eurovan forum):
http://www.thesamba.com/vw/forum/viewto ... light=iscu

[HarryMann]

Thanks Rich, sounds good information and analysis...

PS. Have now Wiki'd most of this thread for future bad idlers (I know how frustrating this problem can be)

https://club8090.co.uk/wiki/Pe ... idling_2.1

[mart 475]

hi rich thanks for your info i'll check it out and get back to you to let you know how i get on and thanks harry for the wiki link. mart

[sonic23]

Hi Mart,
Right - I've got an update for you here. It turns out that my ISCU was working ok......the problem was actually with the Throttle body switch!!!! (Inspite of me testing it on the bench and also hooked up in the van)

Here's the extra set of tests you need to do to establish if it's the ISCU or the Throttle body switch. You will need a multimeter (We've already established that terminal 1 on the coil is feeding pin 17 on the ISCU by you plugging in/unplugging that yellow connector. (This is the idle signal from the ECU)

With everything connected up so that it will hi rev at Idle:

1. If running, stop the engine, then Remove the O/S rear light , hang the ISCU out the light opening so you can get access to it and then remove the ISCU.

2. Start the engine and let it idle from cold

3. You can see on the ISCU connector base (not the ISCU itself) lots of tiny pin numbers. Measure the voltage between 5 and 14. This should give the main battery voltage.

4. We know that your ISV is getting a signal - but for completness, make sure you have continuity from pin 4 to one of the pins on the connector at the cable that plugs into the ISV. Also make sure you have contunuity from pin 11 to the other pin on the connector

5. Now meaure the voltage between pin 5 and pin 8. You should see 5V......If you do see 5V then your ISCU is more than likey fecked.......so try swapping in a replacement.

........HOWEVER - if you don't see 5V it means that your throttle body switch is not closing at Idle....this is what threw me. I tested the Throttle body switch with the motor not running - moving back and forth by hand, and by using the accelerator cable. However for come reason as soon as the engine was actually running, this was enough to not close the switch at Idle!!!!!! The good folks on the Samba have suggested that it was the buttefly valve inside the throttle body that was sticking....that and/or the accelerator cable was just a little too tight.

So.....I've just completely stripped down the Throttle body, cleaned it, very lightly polished it, greased and put it back together. I centred the butterfly valve making sure that it was not bindning anywhere. I then set the switch settings as per bently. (The idle stop first of all, then the actual switch).
Finally I reattached the Throttlebody and then backed off the accelerator cable 1-2mm from where it previously was.

As a result - I now have a lovely normal idle again......

Man that was doing my head in............but i now know a lot more about this system than i did this time last week.

Let us know how you get on,
Rich

[Ray]

I have had the same problem over a long time now. Firstly when on petrol and latley on lpg. Checked for manifold leaks -found none. Noticed yesterday that the coil was arcing and someone had previousy shortenen the coil Ht lead socket maybe to fit it in easier with the lpg gubbins in the way. Fitted new coil today and seeems better if not cured I will further check tomorrow. After reading sonics last post I will recheck the throttle valve which seemed ok but the return action ? abit suspect. Anyway thanks for the useful post.