unstable idle

[SoarerTT]

hey guys my mate bought a GZ70 supra and he is having problems with the car idleing the idle drops to about 500rpm then goes back up to a 1000rpm and then it will sometimes go back to normal but as soon as you rev it the idle goes all crazy again..


please help cheers Ryan

[Toobs]

Could be:
-Sticky ISCV
-Vacuum leak
-Clogged injectors

[30psi 4agte]

Yep id be checking the ISCV mabe oull it out and give it a clean with some carby clean

[brett_celicacoupe]

also check for leaks in the intake plumbing after the AFM.

[SoarerTT]

which is the iscv i dont wanna take the wrong thing off

[brett_celicacoupe]

outlined in red,

the green arrows point to the 2 bolts that fasten it to the manifold

[SoarerTT]

cheers dude thanks for the help ill let ya know how it goes

[SoarerTT]

ok i took off the iscv and cleaned it out and it has stopped doing the idle thing when its just sitting there but as soon as the clutch goes in now it is doing it again what could it be????

[Toobs]

So you put the clutch in and it idles lumpy? maybe your pressure plate or flywheel are unbalanced.

[limbo]

Is it a factory computer?
Try the general stuff now. Change new plugs, clean the dizzy connection points, check the ignition leads are all fixed preoperly, Check earths are all ok, clean the throttle body with some in throttle body cleaner.

Also does the injectors sound ok? they may need a cleaning.

Then if all is still stuck you should take it to a mechanic and ask for a diagnosis cos with the limited info you've given it could be anything.

[EldarO]

is everything fine higher up in the rev range, as in, is the idle the only thing thats funny...?

because if its only the idle, it sounds very much like a vaccuum leak to me.

also, the GZ70 doesnt exist, its either GZ20, or GA70, but thats just me being particular, doesnt really matter

Eldar.O.

[SoarerTT]

yeah sorry its a GA70 i own a GZ20 and i just wasn't thinking straight. were changing the plugs tomorrow and the vaccum lines hopefully that fixs the problem.

[JustCallMeOrlando]

Ahh the joys of AFM's. After dicking around with my 1GGTE a lot, I'll take a stab and say it sounds like an air leak. Even a minute one seems to cause a problem on these engines. Get a piece of 5mm vacuum hose or similar, get the engine running, stick one end in your ear and start putting it around all the joins, it makes it quite easy to hear leaks this way.

They also tend to be a little particular with their ignition timing at idle, bridge the terminals in the diagnostics box and make sure it's sitting on 10 degrees. If he's just bought it, who knows WHAT they've done to it previously.

If you get stuck, drop us another line, if there is a little problem that happens with these engines, chances are Mr Chump (i.e. me) has found it