I have a '92 rs T-5 I have done a 5.7 tbi swap in with a mild cam,intake and headers,and of corse the tbi off the doner truck.when I start the car cold it idles rough and is running rich.(I have had the computer modded also thru howell engine perf) Well I also notice a noise like the tbi is trying to get more air thru a small hole?after it warms up and I drive it for a little bit it smoothes out and runs fine...well I checked it out best I could and seems to be coming from around the IAC.I have replaced it with a new one and it is still doing it...I'm baffled so any help is appreciated....Thanks

I dont know if this is related to your problem, but I know that my car, if the timing is way retarded (like with the wire disconnected) and maybe the dizzy isnt in the right place, the TBI makes a "hissing" noise, like it is trying too hard to suck air in.

Also, even with just the wire unplugged, and therefore 0* timing, the idle quality goes down the shitter. It runs rough and constantly surges from really low to normal and back to really low RPM's. Plug the wire back in so the computer throws some timing at it, and it runs fine.

Just my $.02

the smoothing out part is confusing but the rough idle could potentially be a vacuum leak. when it runs rough take some carb cleaner and spray around all the gaskets and fitting when the idle shoots up and isnt rough once you sprayed you found your leak. maybe the gasket on the throttle body ring is old and brittle and a piece broke off. or something isnt fully sealed.

thanks for the rply...I'll try to see if its a vacuum leak but dont think so cuz it smooths out when warm and runs like a scalded dog.

mine does the exact same thing as yours, as well as it smoothing out and the noise goes away after about 3 or 4 minutes. i've checked for leaks several times......nothing

idle air screw...

just my 2cents..

when you turn it just a fraction, it whistles like different tones, then it disappears when the engine can get enough air in at idle, and the blades closed...

this is saying that you dont have a vaccum leak anywhere. I would never adjust the distributor to fix that sound.. and people say TBI injectors are noisey, when in fact they are not...

just tinker with the idle air screw, i mean just smudge it a fraction!

how do i know? well my TBI used to sound like a supercharger! and everyone said dont worry, just loud / noisey injectors..

the rough part b4 the engine warms up, seems like they didnt tune your open loop proper enough..

Well, I was just making a point. When my car doesent get the required timing advance, it makes a vacuum leak type noise out of the TBI. Not saying he should turn his distrubutor ot fix it, but if his timing was to be way off, then the distributor would need turning!

Also, the injectors arent "noisy" persay, but they do make an audible noise. I think of it almost as an electric buzz.

yeah I'll have to get a retune deffinatly..I know what noise your talking bout but this is differant..even when I open the throttle it gets louder.I'll just have to try to post a vid of it to explain...It really sounds as if its coming from around the IAC but heck I dont know what to check there..lol

Thanks man for the help

the sucking sound is normal. its just the engine drawing in air. my Blazer has TPI, which i ground the wall in the plenum. that wall is there to quiet the intake noise...its real loud now.

by wall in plenum you mean the egr walls? o man so now my tpi is going to be as loud as my tbi was with the open element.