Ongoing tick-over probem

Hi,
Ongoing problem.
Engine ticks-over far far too fast.

Have removed and checked the Auxiliary Air Valve - appears to be working OK.

All vacuum hoses checked for air leaks. All clips replaced with new ones.

Inlet manifold removed, surfaces cleaned, new gasket fitted.

Minimum  air checked. (thin piece of paper then screw in half a turn).

Timing checked.

Brass slow running adjustment at rear of inlet manifold set at about half way.

Engine fires up and runs fast for a few seconds.
Slows right down.
Runs slow for a few seconds and then speeds up again to a very fast tick-over.

Adjustment of the brass screw does slow it down a bit but nowhere near enough.

What else can I adjust?

Thanks







 

My idle control screw (brass screw at back of throttle body) is nearly screwed all the way in.

Have you tried to lower the idle with screwing it all the way in.


Next thing could be the fuel mixture?

Hi,

Thank you for your prompt reply.
Very much appreciated.

Have turned the brass screw right in
Slowed down a bit but nowhere near enough.

Thanks again

How is the rubber O ring on the brass idle screw?

If it's flat and the screw can wobble around then air gets in?

Pictures at the top of this thread when I changed my o ring.

View topic: 1800 DX idle low (Update Now Sorted) - The Mk1 Golf Owners Club

The idle bypass screw should be wrench tight, that is of you can move it with your finger tips, then the o-ring on the screw is shot and needs to be replaced.

If you go to a good hardware store, you usually can find a o-ring to replace it.  I would also suggest that you wrap the Threads and Threads only with PTFE Yellow a couple of wraps of Teflon Tape (PTFE) Yellow is Gas Rated (natural or propane).  

Return it to where it bottoms out, then open it to 1/2 to 1 turn only.

Engines should run enriched until it warms up, then the idle should drop back to 950 on Digi, or @800 on CIS Carbed.  Carbed engines that have an automatic choke, could be that the choke is iffy dirty or leaky.

A hunting engine is usually a Vacuum leak in my experience.  Checking Vacuum hoses is one thing, but I occasionally trim 1/4 inch off the hose ends and re-connect them as they will tighten up.  If you look at them the ends swell, and you should trim that swelling off so you get a good seal.

Is your dizzy Vacuum advanced with points or Vacuum advanced with electronic shutter.

If it was a DIgi, I would say replace the BLUE CTS sensor..

To state the obvious you have an air leak.
There is a pipe at the rear of the throttle body that goes to the distributor, you could check that, also there is a one way valve in the vacuum pipe to the servo, that valve has a take off and there is another close to it on the manifold side, one should have a connection the other a blanking cap, both can break, have a look at that.
If you can't cure it  you could  take the throttle body off and give it a good clean to rule that out.

What speed does it idle at?

Is this when warm or whilst warming up?

If it was me I'd make sure the brass screw has a new o-ring and screwed in before twiddling with other stuff.