Running

I've posted this before but I never got to the bottom of it.

Every year, especially during the cold winter months, my GTA seems to have a habit of the engine dying.

I'll explain:

Start it ok, drive down the road and it's fine. I'm traveling at, say, 30 and the traffic lights go red. I take my foot off the gas and the engine revs just fall all the way to the bottom, engine stops, I gently feed the clutch back in to start it running again.

It's almost as though the ability to idle is just not there after you suddenly take your foot off the throttle.

Only does this when it's cold or at least in the first 5 to 10 mins of driving.
Never does it when the engine is fully warm.

Any clues in the above as to what could be suspect ??

Idle valve sticking .They get oiled up and don't move freely .Give a good spray with some carb cleaner .

Thanks Clee, could you give me a brief description of this valve please?

I guess it's close to the throttle housing ?

Disconnect the two pipes from either side of the valve and spray thro .

Excellent.

Many thanks, I'll do that this weekend.

P

lee, is there a way of "testing" the opperation of this valve, to make sure it is working and hopefully see that it's operation has improved?

Simon,
There is a way of testing this, its in the manual.
If you can't find it i will dig it out.
It basicaly tells you to place an avo on it and explains what it should be reading for closed and open.
Dave

Have a look on the Adaptronic site They are mentioned a fair bit
3 wire Bosch .Middle pin is 12v other two switched grounds ,blahblah .......
Suffice to say mine is playing silly buggers when running on the adapt

yahuh... nuff said

Definitely sounds like the valve isn't opening fully - hence why it idles fine hot (when the engine needs less air) but not when cold. Like Lee says, just take it out and give it a clean. They're prone to this problem, but really easy to fix.

Easiest way to check is does your car idle at around 1000rpm when cold and then around 750 when hot.

If it still idles low when cold ie <900 then the valve is slightly out, or the throttle bypass screw needs adjusting

It idles around 1000 now it's had a new exhaust fitted
(which I must say has improved the car's sound - such a difference - thanks DG)

I'll remove the valve, spray the inside and see if it's any different.
If not then I'll investigate the idle bypass.

thanks for the advice, much appreciated.
Paul

the throttle bypass screw needs adjusting

I thought that idle speed was entirely controlled by the ECU on turbos. Tell me more about this bypass feller. I'm getting slightly high idle speed, even when hot - could that mean that the iscv is closed as far as it can go mechanically and that I need to further restrict the flow by adjusting this bypass screw? Where is it?

There's a small grub screw on the throttle bod itself that sets the pivot arm rest position ,ie closed .This is held in place with a plastic cover and spring clamp .I think this is what Dave means ?

the throttle bypass screw needs adjusting

I thought that idle speed was entirely controlled by the ECU on turbos. Tell me more about this bypass feller. I'm getting slightly high idle speed, even when hot - could that mean that the iscv is closed as far as it can go mechanically and that I need to further restrict the flow by adjusting this bypass screw? Where is it?

You could just have a high idle due to an inlet manifold leak, or vacuum pipe etc, or bleed valve in a post throttle body vacuum pipe (if fitted)

The TBS is different to what Lee said. It circulates a small amount of air past the throttle plate internal to the body. If its open too far, it will idle high. I havent got a body here to hand to look at, but its very small, about 1.5mm in the side of the body, top edge..

Another thing that can happen is the ISCV has two main parts, the body, and a bottom case that it sits in (secured by two tabs). The whole thing can get loose with age, and Ive had some where if I twist the top independantly to the bottom, you can alter the idle speed, as your effectively rotating the valve a couple of degrees, thus throwing out the correct base idle speed. The other downside of this is it can leak too..

Air con equipped cars also have a trigger to up the idle speed as well when activated...