Low Idle Cold - High When Hot

[Ricardo 0]

OK I've read every thread I can find on high idle. (about 1200rmp) So I'll apologise for asking the age old question....what do I check now?

 

I've a Skimmed head with new gasket last year, K&N filter, Magnex exhaust. 106K miles

Revs past 6K OK, Pulls from low revs no pinking

If I set the idle low when hot with the idle mixture screw it stalls when cold. Tried lowering the revs using the adjustment allen fit screw on the AFM.

 

I've cleaned the idle mixture screw.

I've checked the SAD - OK (idle drops when pipe pinched when cold but doesn't when hot)

Throttle cable doesn't stick.

No breather/air pipes leaking.

The Breather/filler bolt is tight.

When the TPS is disconnected when high idle the revs dip for a sec then back up. When 2 pins shorted the same happens.

Cleaned all the hoses (need to do every other week or mayo gets down to the throttle body.

The TSScrew still has tamperproof seal in place.

I've also repositioned the tracking on the AFM.

 

I'm now at a loss. the only thing I haven't checked is the timing. Should I just 'tweek' the dizzy a fraction and see? (cos I can't see the timing aperture or marks whilst all the hoses and cables are on to strobe)

 

Should I just live with it? Getting 25 mpg and whiff of fuel with window open (can't find any leaks).

Please anyone!!! (What about ECU temp sensor? could this be the prob?)

Edited April 28, 2008 by Ricardo

[simonb 0]

1. Sticky TPS switch holding the throttle spindle open. Try resetting the TPS again and oiling the spindle inside the throttle body.

2. AFM spring tension too slack - try tightening 3 - 4 notches anti-clockwise.

 

HTH

Edited April 28, 2008 by simonb

[Pug_Power_Dave 0]

I've had this before, and found it was just due to not being enough slack in the throttle cable!

So mabe try moving the adjuster down a notch!

[djinuk 2]

ive got this exact problem aswell, Car idles when cold around 900- to 1000rpm, when warm it sits at 1500rpm, but when you blip the throttle it drops back to 1000 then raises back up within a few seconds

[simonb 0]

If it's the throttle cable just unhook it to test and rev the car by hand. That will tell you where the problem lies. If it still does it, move on to.

 

Sticky TPS,

Air leaks,

AFM spring

[dani959 0]

My bets will go to SAD.

 

Make sure it is pointing the right way (plug side to the front of the car).

The SAD is adjustable. If you slack the 6mm nut and move it, you can set a bigger opening when cold. It will still close when hot. This will raise the idle when cold. While you're at it, clean it well with carb cleaner or something like that and make sure it moves freely.

 

Cheers and good luck!

[Ricardo 0]

I've had this before, and found it was just due to not being enough slack in the throttle cable!

So mabe try moving the adjuster down a notch!

 

Tried that cheers but not the cable.

 

I'll try the SAD adjustment, didn't know they were adjustable!

Also try the AFM spring tension if the SAD does adjust.

Now the weather is a bit dryer and warmer (maybe!) the difference between hot and cold idle is less.....still about 1000-1200 tho!

 

I will persevere...Thanks for all the input.

[GLPoomobile 958]

I'd be loathe to mess with the AFM spring. It's one of the things that dictates the fueling through the rev range, so really needs to be right or you'll run too rich or too lean.

[Ormy 0]

I was going to suggest cleaning the SAD but been beaten to it.

 

Couldn't help but notice you're from Ulverston, that makes two of us!

[Project205 0]

Hi,

 

I am suffering from the same symptoms as Ricardo describes.

 

I have carried out the following so far:

 

Tested the SAD - Working well, very clean

Cleaned the idle screw - Stunning

Tested TPS - Clicks when throttle is depressed

Checked tension of thottle cable - fine, not overly tight

 

What is next?

 

Clean Throttle Body?

New ECU Temp Sensor?

Test Air Flow Meter? Is there a simple test that anyone can advise me on?

 

Just to re-confirm the current situation, I adjust the idle screw on throttle body so that the car idles when cold (set to about 900rpm), then as the car warms up and the oil thins, the idle gets higher and remains at 1100rpm (unless I adjust it back down again!). What I would expect to happen is for the idle to drop once the car warms - as it did with a 205 gti I once owned.

 

All this talk of 205 GTis never idling properly is not true, one I had years ago which idled perfectly, cold and hot.

 

Any help greatly appreciated.

 

Many thanks.

[Project205 0]

Someone must be an 'idle' expert!