94 454 TBI High Idle?

[Afireinside]

Okay if anyone saw my last thread I had a few problems.Seems like I got all of them fixed except one.I constantly have high idle at start up its like 1500rpms for about 2 seconds than down to about 1200rpms till it warms up than down to about 1050rpms.I thinks it should idle about 600 and Ive been keeping the tranny in neutral at stops but other people have to drive this and I dont want to burn up that exspensive 4l80e.
I had a few people say TBI base gasket but I took it to emissions and it passed great.So could it still be gasket?
It does take a while to warm up fully so could the temp. sender by the t stat housing cause this?
The 454 has a weird throttle modulator on the TBI that the 350s don't so what does this do?Do you think it could cause this(I did hook the modulator up to manifold vacume and it seem to work) any ideas?


Thanks a lot for all the help

 

[bigbadchev84]

I Would Bet It Is The Gasket, We Have A Truck Here At Work That Had The Same Problem

 

[rcpilot]

May not help but my '89 454 had a blown fuse in the fuse block labeled "guage/idle" It was blown when a wire was re hooked to the battery for an amp... after that it would idle high for longer than normal...replaced it and the idle now seems to be normal after start up... just an idea BTW my volt guage had stopped when the fuse was blown..thats how I knew it was blown...

 

[Afireinside]

If I had a bad gasket it could still pass the e test that well?

Thanks for the replies all

 

[bad_bo_ti]

is the tps (throttle position sensor) good or adjusted right? you should be able to check this with the engine off, i think the key has to be on though, you need a volt meter to check, locate the blue wire going to the tps and probe it with the red + side of the voltmeter, conect the other end to a good ground, with the throttle completely shut it should read around .5 volts and at wide open throttle it should read 4.5 volts. if you have a higher reading than .5 volts with it shut you need to adjust the tps if adjustable or replace it. to adjust just loosen the 2 screws holding it on and twist either up or down untill you get to the .5 volts. hope this helps.

 

[bad_bo_ti]

check this out they have the write up for the tps and the iac sensor http://www.thirdgen.org/newdesign/tech/tpimod2.shtml

 

[sweetk30]

3 bolts and about 5 min and 3-4 dollers and you will know if gasket or not and by then but new in. if still there go to shop and ask for smoker test. its a machine that will help find leaks and pinpoint the problem.

 

[1985K20]

With the engine idling, grab a propane torch, take the end off and put a rubber hose on the end of the pipe.Now you can spray propane around all the gaskets(throttle body,intake,vac. hoses) to see if ya have a vaccum leak, if you do; you'll notice your rpm goin up some as soon as the leak will suck in the propane.

 

[Afireinside]

Thanks for the replies and thats a great link i'll try it in the morning.
Thanks