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Model specific boards => Golf mk2 => Topic started by: catch on 28 August 2007, 18:53

Title: car won't rev smoothly
Post by: catch on 28 August 2007, 18:53

I’ve got an issue with smooth revving on my 16v k-jet.
When I rev the car above 3000rpm and then let go of the gas the revs seem to stick at 1800, jump back up a little for a moment then drop back to a smooth idle.

I’ve checked the cable and that seems to be ok

Any ideas?

Title: Re: car won't rev smoothly
Post by: RickyC on 28 August 2007, 19:31

check plugs, leads etc first,

Title: Re: car won't rev smoothly
Post by: golf8v on 28 August 2007, 19:34

plug and leads not likely to affect idle. most coming problem would be idle air control valve..

Title: Re: car won't rev smoothly
Post by: catch on 28 August 2007, 19:41

The plugs are 3 months old and the leads are all clean. The car runs perfectly apart from this.
I have cleaned out the isv and it buzzes when the ignition is on. Could it be the throttle valve switch? I've seen it in the Haynes manual but not sure what it does exactly...

Title: Re: car won't rev smoothly
Post by: RickyC on 29 August 2007, 01:29

Quote from: golf8v on 28 August 2007, 19:34

plug and leads not likely to affect idle. most coming problem would be idle air control valve..

yeah my bad, read it too quickly, check the idle control valve as said previously

Title: Re: car won't rev smoothly
Post by: catch on 29 August 2007, 09:32

Ok. thanks.  I'll unplug the ISV and see if the car revs smoothly.
If it does, how do i know if the problem is with the ISV itself or the controller behind the centre console?

Is there a test for this?

Title: Re: car won't rev smoothly
Post by: Gambit on 29 August 2007, 12:50

check the throttle closed switch is working correctly

Title: Re: car won't rev smoothly
Post by: Mk1Mad J - 16v on 29 August 2007, 17:30

The over-run cut-off valve should be doing something when you let of the throttle, maybe it isnt doing what it should  :smiley:

Title: Re: car won't rev smoothly
Post by: catch on 30 August 2007, 16:25

I tested the throttle valve switch with a multi meter as per the Haynes manual. All readings are fine and you can hear the switch click on and off. I cleaned out the throttle body although this was pretty clean to begin with. I tested the revs when the isv was disconnected and the problem is still there so I don't think its that.

This leaves me thinking its the the overrun cut-off valve.
Has anybody ever cleaned one of these things? Is it actually possible to clean it or is it a sealed unit?

Title: Re: car won't rev smoothly
Post by: Mk1Mad J - 16v on 30 August 2007, 16:36

Will check my manual when I get home, there should be a vacume line on the over-run valve too, is that missing or damaged?

Title: Re: car won't rev smoothly
Post by: catch on 30 August 2007, 21:40

All the pipes are connected up to the valve and seem to be in good condition.
Would the ECU have anything to do with this?

Title: Re: car won't rev smoothly
Post by: catch on 01 September 2007, 11:26

Tried disconnecting the overrun -cut-off valve - no difference.
If i rev the car and then press the throttle valve switch by hand the revs drop then climb back up a bit. Is the normal? Or should it stay idling when this is pressed?

really starting to run out of ideas now.....please help!  :undecided:

Title: Re: car won't rev smoothly
Post by: catch on 02 September 2007, 15:49

Now i've cleaned out and tested the overrun cut-off valve according to the Haynes manual. The meter readings are all fine and i can't hear the valve working when i press the throttle switch.

So....what's left to test?

All I can think is the control unit behind the centre console is knackered. Anybody got a test for this?

Title: Re: car won't rev smoothly
Post by: Mr Blue on 02 September 2007, 16:03

Try the air flow meter.

Mine is not idling smoothly and have narrowed it down to this

Title: Re: car won't rev smoothly
Post by: catch on 03 September 2007, 14:23

I've cleaned the airflow meter now, a little bit of old oil in there but not much.
I've done all the checks on the airflow meter according to the Haynes manual and it seems to work perfectly.
The plate is set up correctly and it moves freely in all directions.

So what's next. The Haynes manual says to change the controle unit behind the centre console. I thought all this did was regulate the ISV though????

Any ideas would be very much appreciated!  :cry: :cry: :cry: :cry:

Title: Re: car won't rev smoothly
Post by: catch on 14 September 2007, 15:27

anyone that can help?

Title: Re: car won't rev smoothly
Post by: markmarky0 on 14 September 2007, 21:53

i have this exact same problem , its really anoying me and sounds like im a noob racer trying the rev around at every stop !
I tried cleaning the ISV still no worko,have a feeling it might be the gaskets somewhere leeking air :s , throttle body maybe i dunno.  let me know how it goes,
Mark

Title: Re: car won't rev smoothly
Post by: monzablue16v on 15 September 2007, 00:07

Mine does it intermittently as well. I thought I'd cured it when I rebuilt it but I've had it doing the rev to 3000rpm when I stop again recently not amused. :( going to have a fiddle again tomorrow.

Title: Re: car won't rev smoothly
Post by: DarnPB on 15 September 2007, 22:36

Check the throttle body for wear. Where the throttle spindle goes through the body of the throttle, get hold of it and see how much play you have. If excessive, then you will be letting air in and thus running lean, affecting the smoothness. These symptoms will usually be intermittent. I have rebuilt an engine from a Morgan because of a burned out piston caused by this.

Title: Re: car won't rev smoothly
Post by: clipperjay on 15 September 2007, 23:54

Quote from: markmarky0 on 14 September 2007, 21:53

I tried cleaning the ISV still no workoMark

You need to swap out a ISV that you know that works, cleaning it will not work if the things is jamed full of sh!t.
The symptoms are rought idle and high reving around 2k-3K RPM.
MarkIII's have a ISV you can use in scrappie, but this is the most likely common fault with idle hunting.
Unless an idle mixture screw has fallen out from the throttle body which always catches people out.
Other possiblilites least metering head is starving the fuel regulator and injectors of fuel.( a pressure test will tell if this the problem)

Jay