Idling too high

[fuel]

hey guys, thought I would post this newbie question in the newbie section. I've just replaced the head gasket along with the timing belt/water pump/tensioners/oil seals etc on a 1990 4G67 DOHC powered E35A Galant, now before the head gasket blew the idle speed sat at about 700-800rpm when hot and a little higher when cold. After the gasket replacement the idle speed is now 2300rpm when hot, slightly lower when first started cold.

I removed the head with the inlet manifold still attached but had pulled off the fuel rail, and the only other thing I did was run a rag around the edges of the throttle plate and around the inside of the throttlebody to clear off the accumulated muck - but I don't think this would account for a 1500rpm increase of warm idling.

The throttle cable has some slack when the throttlebody is closed and with the intake pipe off I can physically see the throttlebody is closing properly too. The brake booster vac hose is connected securely as is the rocker cover breather hoses, and I cannot hear a hissing noise from anywhere suggesting it has a vacuum leak. The BISS screw in the throttlebody is maxxed out at the lowest idle speed position too.

Anyone have any ideas? On a side note my own VR-4 does a similar thing, when first started cold it will idle at 1500-1600rpm then as it's warming up the revs will further increase upwards of 2500rpm for about 4-5 mins then will come down to 900-1000rpm when fully warm - anyone have an idea why it would rev higher when warming up from its cold start rev amount?

Thanks!

 

[fuel]

that's pretty much what I did by running a petrol soaked rag around the edges of the throttle plate and in around the inside of the throttlebody - how would cleaning the throttlebody cause the revs to drop, if anything it will cause the revs to increase as the throttle would be letting in slightly more air around the edges of the throttle plate where the build up muck would have otherwise blocked the flow. I cannot see an obvious way of adjusting where the throttle plate stops, I see where the idle switch is and I've undone it and backed it off completely but there was no change.

 

Check your throttle cable tension.

 

[fuel]

Quoting cherrod8:
What?

Try cleaning it like it says on vfaq and make sure all the bolts are in.

When you rev it does the idle go down a little or a lot?

Try testing the TPS and ISC, may also want to take out the ISC and clean it.

The coolant temp sensor could be the problem as far as you VR4 goes



Revving it or even letting it idle for say 10-15 mins wont affect the revs - it still sits on 2300rpm. TPS appears to be set correctly, is giving me the proper readings on the multimeter. Will need to test the ISC.

I still think it's the throttle plate is perhaps too far open when it is in its closed position - is there any way to adjust the throttle plate stop position?

 

[fuel]

Quoting Red_Bird:
Check your throttle cable tension.



I did, if you had read my first post.

 

[fuel]

anyone have further ideas? thanks

 

[vtecds1]

Quoting fuel:
I cannot hear a hissing noise from anywhere suggesting it has a vacuum leak.

Try spraying carb cleaner around the throttlebody area. If you hear any change in the idle, then you found yourself a leak.

 

Fast idle air control valve (fiacv)

just replaced mine my idle was shotty as hell

 

[grocery_getter]

You said you removed the fuel rail? Along with the injectors attached to it right? If so then its an intake leak from the injector to head seal. You need 4 new seals (they call it lower insulator) where the injector connect to the head from Mitsubishi. The old seal is already "imprinted" with the old injector pushing on it. The heat from the head turns these rubber seals into hard plastics. Hard plstic seals don't seal like new fresh pliable rubber anymore. Need good fresh rubber to seal correctly.

 

[fuel]

yeah I did think about the injector seals they did seem a bit hard - will try spraying brake clean around the seals to see if the idle improves.

 

[KiNgMaRtY]

Your FIAV could be toast, especially if you sprayed it with TB cleaner and didn't block off the holes. Try blocking it off. Next if not it, I would try the swapping the ISC. I went through this process to fix my idle on 611 when it would idle at 3K! Started of low and got higher and higher

 

[fuel]

I'm guessing the FIAV is the wax valve which is controlled by the coolant lines to the throttlebody? I didn't spray any throttlebody cleaner to clean it out, only a slightly petrol soaked rag to wipe the muck off.

I think I'll check the injector seals and if that doesn't work then look at the throttlebody closer.