This is a 1991 305tbi 5spd.

Maybe my title was a little strange but what's happening is when I push the gas pedal down more than half way and let go it doesn't immediately throttle down. It stays revved up for about three seconds. I know it isn't supposed to immediately drop but it shouldn't be staying revved up this high.

Ok, the throttle cable is messed up right? I replaced it a couple months ago and figured I probably got a bad one. So I take the air cleaner off and rev it by hand. I can see the butterflys fully closed but it's still revved up and making a weird noise (probably from trying to suck so much air around passed the butterflys). So it's not a problem with the cable. And furthermore I'm baffeled how it is revving up with the butterflys closed.

Next I pulled the throttle body off and apart and thoroughly blasted it out with throttle body cleaner. I got tons of gunk and grime out and re-installed the throttle body with RTV and a new gasket.

Does anyone have any ideas? I'd greatly appreciate any help.

 

either you have a vacuum leak or your IAC motor is sticking. I'm leaning toward IAC since it only does it after you rev.

 

Vacuum leak for the win. Thanks. Now the throttle cable is sticking though. I can't win with this thing.

 

Worn TBI will cause this. The base wears around the throttle shaft into an egg shape and the throttle blades hang on the bores under vacuum, causing the engine to have a fast idle. Way to check is to open the throttle (at the TBI itself) half way by hand and try to move the throttle shaft around. If it can be moved at all, then the TBI is worn, and can cause issues. If it moves a lot, you've found your problem.

 

I have a very similar problem. Even when I just open the throttle a little bit, it wants to keep idling high. When coming to a stop, if I rev the engine, the revs will come back down and idle normally. I have cleaned the throttle body, but that didn't seem to do anything.

 

Happens on anything with a throttle... TBI, TPI, Carb, whatever.

 

It there a certain amount of play that is acceptable, or is any play grounds for replacement?

 

I'd guess a bad IAC valve. Mine likes to stick randomly for some reason. The other morning on my way to work I was idling at 1400 out of gear, 1200 in gear and it was pulling like made at a stop. About half way to work it had a sort of hicup, nearly died when coming to a stop and then all was well again. I'm not about to pay 90 bucks for a new one though. I've got a 454 throttle body on mine, different IAC and of course a higher price.