DJ 2.1 idle problems

[beigewedge]

hi...having problems with the idle on my '86 bus. its a digijet system...
bus will start up and sit at idle, but when revved just drops to zero and stalls, or bounces back up to idle...

it used to do it very infrequently but now its all the time, cold or hot.
lt starts straight back up but then does it again say at a traffic light or junction . I have checked crappy idle stabilisation unit thingy, and it does the same with or without it plugged in! also cleaned out idle control valve, which appears to be working and checked all hoses for leaks... still the same!!!

anyone with any ideas?

[tonytech]

When you 'unplug' the ISU do you join the two plugs together??

T

[Bugger it]

My 2.1 did this and it drove me up the wall. I did what you have done and still did the same. So I put some injector cleaner in with the fuel the STP stuff and its a lot better it does in every now and then but its a lot better.
I'm booked in at Aldon for a rolling road tuneup on the 14th I'll let you know what he says it is. It could be my Weber Alpher ECU tho, but if somthing simple I'll let you know.

[beigewedge]

I have tried the cleaning route and it works for a while... but its not a fix.
its now really annoying and undriveable!
any more info would be greatly appreciated... many thanks.

oh, i did plug the ISU plugs together...

im off out to buy some big fat carbs!

[Grun]

beigewedge,
I've been doing my usual and have a nose through the manuals I have, over a cuppa after breakfast. Nice being retired, and one way of learning
Have you had a look at the throttle valve switch ? Operation / adjustment / ohmmeter across the switch terminals?
If you do not have the manual, can pm you with the info. I also have the engine management manual, which only covers the Digifant system, but a lot of it is common or similar to the digijet I think.
I had similar problems, but they seem to have been caused by standing unused for a bit too long in a cold garage. I did set the base idle speed a little higher to make the thing driveable while sorting it. May need re setting at the next MOT to meet emission regs.
Mike

[hammy44]

hi i had a new engine fitted and it was terrable to drive and cut out on idle and give whip lash whilst driving three different mechanics all went down the electrics route and as a last resort i tried redex fuel treatment after 3 tanks through it it now runs perfect its awkward to describe how bad it was but believe me it was diabolical its worth a go

[andyj]

I had very similair problems on a 2.0 8v Seat Ibiza I bought recently, and the cure was to clean the butterfly valve in the throttle body.

Now, I'm not sure if this will apply to the older VW engines like yours, but with it being injection rather than carb, I think it might.

What I found was that lots of oil residue was being kicked up from the crankcase, through the crank case breather pipe. The pipe vented into the air inlet, before the throttle body. Therefore all the oil residue was covering the inside of the throttle body with 'gunk'.

This meant that the butterfly valve couldn't operate properly!

Took me an hour to strip it down and clean it up, but job sorted!

Also, might be worth checking if tere are any vacuum pipes that have become disconnected. The ECU will use these to trigger the idle valve to work. If one is disconnected etc, then the ECU won't open the idle valve when it needs to.

Hope some of that might help you out !!!!

Andy

[Aidan]

check the throttle body switch is switching at idle, sounds like it isn't reliably doing so, hence isu checks out, but if not being told to work by the throttle body (ie "he's got his foot off the acceleator, please help me to idle" )it doesn't do anything : )

this one keeps coming up, don't know what's in the wiki for diagnosis but the digijet and digifant guides should be there.

[beigewedge]

many thanks for all advice... will check switch and throttle body and give it all a good clean and see how it goes... it might be a case of bus standing too long, as it did it less when it was my daily driver. we will see... theres a lot of traffic lights between here and the alps! if all fails i will fit a big red starter button in the middle of the steering wheel

[beigewedge]

righto... ive had the throttle body off... cleaned out the bugger cos was a bit dutty and blasted the idle control valve and all pipes and tubes with carb cleaner... also reset the switch in the throttle body and checked da electrics... fun fun fun!

bolted it all back up and its seems to idle once more!

off to france then.. wish us luck!

[Grun]

beigewedge,
Well done Have fun in France, I set off cross channel after sorting my idling probs, and had a trouble free 1500 miles or so there. Hope you are as lucky.
Mike