fuel
Well-known member
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!
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!