2.1 DJ fast idle

[Ashwood]

Hi,

My automatic 2.1 runs well with plenty of oomph, but when I stop and put it in neutral she idles fast, (it’s like if an automatic choke is stuck on) then when I put her back into drive, it gives a jerk forward due to the high revs.

Be grateful for a head ups on where to start with slowing down the idle speed. I’m looking in the Haynes manual and it mentions the idle control valve, which seems a good place to check first?

Many thanks,
Ash
 

[maxstu]

Has it always suffered fast idle? Or only after recent engine fettling?
There is an idle speed adjustment screw. But not sure if that is your problem. The large slotted round item in centre of photo...on the throttle body.

If it were my problem l would start by checking timing or vacuum between dissy and plenum, and go from there.

[Ashwood]

She did fail this years MOT on emissions, so the guys did fiddle with the engine to get her to pass. But previous to that she was still running quite fast on the idle, but def worse since the MOT.

I’ve never checked timing on an engine so not sure what to do.  Maybe I should get that Haynes manual dusted down again!

would a local garage be competent tuning the DJ engine, or would it best be taken to a classic VW garage who knows the DJ system inside out?

cheers.
 

[maxstu]

Old skool VW garage in my opinion. Or perhaps a local mobile engine tuner?
Whereabouts are you?

[Ashwood]

Mid Wales!

[Smiffo]

I don't have a Digijet system myself (yet) but is it something silly, like sticky or misadjusted throttle cable?

Just disconnect it at throttle body and see.

Is the idle consistently high, or does it hunt up and down?  

[maxstu]

John at .....

https://vwcamperhaus.co.uk/

He worked with one of best in the business. The late great Steve Shaw at Gasure. So will be familiar with the Digijet system

[maxstu]

I don't have a Digijet system myself (yet) but is it something silly, like sticky or misadjusted throttle cable?

Just disconnect it at throttle body and see.

Is the idle consistently high, or does it hunt up and down?  

Good point. Any slack at the accelerator pedal?
It's cable operated from pedal to auto transmission kickdown lever. From thereon a solid bar. Release spring pressure at the throttle body and see what happens, perhaps?

[tobydog]

Air leak?

[ajsimmo]

A bad connection at the temp2 sender, or faulty sender would cause the idle speed to increase significantly. The test is to unplug it and see if it increases further. If not, it's probably that, or the control unit behind the RH rear light. If it does make a big difference then that system is working and the cause is elsewhere.
My pick-up is an auto, and tends to seize a bit on the gearbox relay lever/cable mechanism, resulting in a slightly raised idle speed. If you pull back on the throttle rod (towards back of van) does the idle return to normal?

Sent from my moto g(30) using Tapatalk

[Ashwood]

thanks for all the info guys.

the fast idle is constant, no hunting at all, but if i give it the full beans on the revs and then back off, she then goes down (not always) to a slower idle but then quickly creeps up to the fast idle.

I've fired up the bus and checked the throttle linkage, all seems ok and the throttle returns back to its stop.

I've also checked the idle flow valve. Resistance was 5 ohms which was within the recommended range, connections looked tidy and it did seemed to vibrate when i revved up. So assume that is ok.

Will look at Temp2Sender next.

I'm near Builth so Camperhaus bit of a trek, but could consider if we are heading that way .

 

[Ashwood]

Struggling to find temp2 sender - could you direct me to it please?

[Smiffo]

This is for a late van. ( Unsure what year yours is. )
Don't worry about his symptoms yet, just watch through until you see engine bay, and he directs you to where it is.

[ajsimmo]

LHS of thermostat housing, blue sender, usually blue plug. Just push in the clip and pull the plug off, revs should go up (ecu "sees" a high (∞Ω) resistance indicating a cold engine, so opens idle air bypass valve more). Plug temp2 back in, revs should drop again immediately.
Have you tried screwing the big idle screw in a bit? And have you checked the vacuum hose is on the retard side of the can on side of dizzy, and it's working?

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[Ashwood]

Yep, found it, unplugged it and revs went higher. Reconnected and revs dropped to the fast idle in about 5 seconds.

will try the big idle screw next, just turn clockwise?

is the dizzy the distributor? Technical mechanics talk?!