Variable idle characteristics. Possible causes?

[masterofsinanju]

I've got a stock 1ggze. When I first got the car, drving from cold start was a problem until I replaced the cold temp sensor. Now it runs fine.

However, the idle properties are a bit all over the place. Sometimes it sits on 2000rpm without changing when it goes from cold to hot. Sometimes it goes hunting between 1000-2000rpm but most often it idles smoothly at about 800rpm.

I've cleaned the ISCV and it's possible I haven't got as good a seal as possible with the new gasket and goo but are there any other things to check before I go pulling it out and redoing it? It's a bugger to get at and I'd rather consider what else needs doing.

Also, is there any way to stop cold start idle from being so high? I'm not a big fan of the 1 second or so before the oil pressure comes up and hearing what I presume is an ungood rattle.

[4th surf]

Cripes it's been years since I've worked on one of those as most of the Chasers, Soarer and other models that had them back in NZ (the land of many imports) went to the "Big car graveyard in the sky" years ago due to "Car Cancer" .

But you're looking at one of 3 things. 1. Vacuum leak (intake manifold, split hose etc), 2. Air leak between intake manifold and airflow meter (e.g broken power steer "Idle up") or 3. Faulty air flow meter.

You can either get some CRC or carby cleaner and spray it around all the joins and hoses on the intake side with the engine running and when you spray a certain area if it either settles down or dies off that's where the problem will be. It may also be an idea to "flash it" for codes. There should be some terminal blocks in the main engine harness near the firewall somewhere which have like a blanking plug on them, one of these you connect to ground to get the codes. www.troublecodes.net may help you there. Also IIRC these are based on a Bosch L-jetronic system so should have a cold start valve somewhere on the manifold. It will have water hoses going to it.

This is of course if I'm thinking of the right engine as the "GZE" may have thrown my train of thought. Still check for codes and carry out the checks that I've mentioned and go from there as this is likely to be something small and stupid that takes a while to find

[masterofsinanju]

Thanks surf ill have a crack at it tonight.

[dumbass]

If idle is rough and up and down abit all the time then its prob a leak
But if its idling very high one minute then for no reason drops right down
It's more likely yr idle motor
Air leaks will have a more consistent problem compared to idle motor stuffed which changes
From hi to low instantly

Put a nut inside the feed hose to the idle motor
Prob 12mm hex nut with 8 mm hole in middle is good size to keep the cold idle to around1300

[Hiro]

What is the cold idle circuit set up? Classic thing for 4AGEs is to get an air bubble in the cooling circuit that sits at the highest point, which just happens to be the wax pellet valve in the cold idle, this causes the valve to flutter around between cold and warm idle even when the car is fully up to temperature.

[masterofsinanju]

Well no detectable leaks, but it has been suggested the TPS bears looking at.

I'm told their are two sensors, one for throttle position and one for idle and it might be not quite reading right and I might need to consider if the ECU is supposed to have a speed sensor: