Idle speed too high

[SootySport 23]

My idle speed is to high when engine is at normal temperature.  I’ve backed off the throttle by pass screw to closed position and  butterfly screw is closed up as far as it will go but it still idles at 1400rpm.

  When I block the airflow going into the AFM the engine stalls as it should, so that tells me there is no other air leaks after the AFM going into the inlet manifold so what have I missed?

[welshpug 1,661]

start from scratch with the inutial throttle settings, all covered in the haynes workshop manual.

 

is the oil filler pot bolt present?  this will cause a high idle but not sufficient air to run in its own.

Edited February 1, 2021 by welshpug

[SootySport 23]

The bolt holding the oil filler is there.   I’ve been through the Haynes set up quite a few times but haven’t a vacuum gauge, is it really necessary?

[welshpug 1,661]

no I've never used one.

[DamirGTI 342]

Might be the TPS holds butterfly under tension , lifting it crack open for the air to flow past it while idling .

Try to loosen the TPS mounting screws and let it rest like so losely , making sure that the butterfly is fully closed , start up and see what happens . 

 

Other , could be ignition timing advancing bit too much .. if you've been doing something lately with the dizzy or it might've loosen off and moved a bit .

 

D

[SootySport 23]

9 hours ago, DamirGTI said:

Might be the TPS holds butterfly under tension , lifting it crack open for the air to flow past it while idling .

Try to loosen the TPS mounting screws and let it rest like so losely , making sure that the butterfly is fully closed , start up and see what happens . 

 

Other , could be ignition timing advancing bit too much .. if you've been doing something lately with the dizzy or it might've loosen off and moved a bit .

 

D

Thanks,  need to go back to timing as it’s never been done by me but was done by previous owner and was idling ok when I bought car, although I’ve never disturbed the dizzy cap.