Erratic Idle on MAP 4AGZE

[PooJou]

Hey guys,
I've got a MAP 4agze powered SX (takai's old car) and it's got a really odd idle, which before only came up once in a while (then settled) but now is quite regular. It sits there going steadily up and down between 1100RPM and 1500RPM - can anyone suggest what is wrong? People have said "vac leak" (which i havent checked yet... and there a bazillion hoses lol) but im thinking if it was a vac leak, it'd be idling like that ALL the time (which it isnt)

Thanks in advance guys

[Rallystanza]

Sounds like a problem with the idle speed control valve......ISCV.

There is a thread somewhere in the FAQ on how to clean the ISCV and prolly solve the issue your describing.

http://www.toymods.net/forums/showthread.php?t=3535

Seems to be more related to the ISCV on a 1G but check it.

Jeremy

[Ben Wilson]

Get a multimeter with duty cycle function and hook it up across two of the terminals of the ISCV. Get the car to normal operating temperature, then adjust the idle bypass on the throttle body until it reads around 50%.

That fixed it last time he had that problem, the extra inlet length with the front mount makes it hard for the computer to adjust nicely, so the TB idle adjustment needs to be spot on.

You'll probably have to do it every few months or so (ZE's are well known for idle problems).

[The Witzl]

has anyone ever put their multimeter on the ISCV to read the frequency at which the ECU is switching it?? I'll tell you now is farken LOW!!!

Hence why you get the erratic changes - a change in the ISCV wont show on the engine's RPM until a few moments later...... so if the change was too much one way or the other.... well you get the point...

[Ben Wilson]

LOL - With my inlet setup, I worked out that air was taking around 3 seconds to get from the throttle body to the engine at idle. It took a bit of fiddling to get anything like idle control...

[takai]

It isnt really a vac leak, but in some ways i guess it is. Basically as the others have said it is the ISCV over-compensating and causing the rise fall issue.
Ben has fixed it in the past, and it is a matter of fiddling with the idle screw. It also changes a fair bit as the weather gets hotter/colder.
Failing that you can clean it (again, i did it in August/September), or simply find someone who has gone turbo and replace the ISCV.

[PooJou]

It isnt really a vac leak, but in some ways i guess it is. Basically as the others have said it is the ISCV over-compensating and causing the rise fall issue.
Ben has fixed it in the past, and it is a matter of fiddling with the idle screw. It also changes a fair bit as the weather gets hotter/colder.
Failing that you can clean it (again, i did it in August/September), or simply find someone who has gone turbo and replace the ISCV.

I'll go have another fiddle with the idle screw, i seemed to fix it when it was warmer, but now it's cooler, i think i need to drop it back a bit.... DAMN melbourne and it's completely random weather :/

EDIT: anything else you guys want me to have a squiz at??

[takai]

Yeah, when i was driving the car daily in Melbourne it was a bit weird with the weather. But then i started walking and cycling places and suddenly it got better... or maybe i just didnt notice it as much.

[PooJou]

Yeah, when i was driving the car daily in Melbourne it was a bit weird with the weather. But then i started walking and cycling places and suddenly it got better... or maybe i just didnt notice it as much.

Lol, i'll be walking and cycling soon don't you worry - must be just our random weather messing with it