Hi, i'm new in the forum, i'm an italian boy with a '89 convertibile camaro iroc-z with 305 TBI.

I have a big problem with my car.
My idle is very high (2000rpm) and my automatic transmission don't found because of this.
I have to have the idle in 600 rpm how is normal.

I have changed all sensors!
My IAC is good, and my TPS is good.
I think that i have a vacuum leak, but i have controlled all the tubes and I found no loss.
Thinking it was the gasket under the throttle body I tried to sprinkle a little 'fuel spray but it had no effect, so even the gasket under the throttle body should have no problems.

I tried to exclude the EGR tubes, cruise control and brake assist, but to no effect.

I ran the IAC reset but nothing has changed.

Now I do not know what to do and I hope that someone here in the forum will give me advice effectively.

It could be the temperature sensor? (The one that goes into the air filter)

Thank you!

 

Sorry it took awhile, yes the tbi base gasket is a known source of a vacuum leak.
Remove the linkage & make sure the throttle is closing all the way too.

 

2000 rpm idle is most likely a vacuum leak.

Like ex-x-fire said..tbi base gasket. The material gets dry and brittle over the years. It's easy to pull off the tbi unit, so I would do it anyways. Also, a bad pcv valve and/or pcv grommet can be a difficult to find vacuum leak. Pull the vacuum line and plug it with your finger to see if any major drop it idle rpm.

The IAT (temp sensor at air filter) should have no major effect on idle RPM. Although, if the CTS (coolant temp sensor) on the front on the intake manifold is not functioning properly, then engine will not idle down as it warms up.