350 TBI Running issues...

[OldSchoolGuy7]

My poor Camaro....
Okay, Its a 1988 Chevy Camaro, w/ a 350 5.7Lin place of the O.E.M. 305 5.0L. Its not the Vacum Lines, Injectors, Filter or Sensors. although the computer does throw codes for the TPS, O2, MAP/MAF sensors. The engine Idles @ 2500-3000rpms. On start up the engine will start normally & idle down to about 900-1000rpms, w/ no issues, then I hear a large "whosssssshh" sound as if air is being sucked in or out, & alot of it. As soon as that noise starts, the engine jumps the Idle up & will not come down unless the noise somehow randomly stops. The car has had a full tune-up, All new ignition, all new cooling & all new fuel system rebuilt & almost every sensor changed. Also is running w/ a FlowMaster Duel Outlet Exauhst system 3inch Cat.Back. I cannot find where this noise is comming from but it sounds like it comes from the back side of the engine (where it meets the firewall/windsheld) The car only runs @ a high idle when this noise starts, Could it be a bad intake gasket?? that is my last guess.
Please help!
-Charles

[BmXRacR96]

Sounds like intake gaskets to me. On a cold start(in the morning) take a can of carb and choke cleaner. With the engine running spray a small amount down where the heads meet the intake manifold. all the way along from front to back, both sides. If the idle raises even the slightest suspect a bad intake manifold gasket.

Other things to check intake gaskets for

Coolant leaks
White smoke out exhaust and may also have a sweet smell/taste to it.
Coolant on top of engine
Losing coolant
Leaking oil (not very common, but possible)

Another thing to check is the IAC, Idle air control motor. Which does exactly what it says. Make sure its pluged in. Sometimes a temporary fix for testing would be to tap on IAC housing (metal part) with a small heavy metal object. Sometimes it will free up the valve inside. Returning it closer to a normal idle

Doug

[OldSchoolGuy7]

I have replaced the IAC valve also & did try tapping on the old one before I replaced it also, to no effect. I'll try spraying some carb&choke cleaner around the Intake & see if the rpm's rise.

I'll repost when I figure it out or give up & take it into the shop.

[OldSchoolGuy7]

Problem Solved

Well, I took it into a shop to have checked out. It ended up being a wiring harness & connector. It made the computer think the engine was running wrong, & it was opening the IAC valve all the way which caused the noise & rpm's to rise.
Well the car is running back to its usual bad self
Gotta love all that torque.

Next step is all new springs, lifters, rods & valve covers. Any sugesstions on which brand & spec's I should go with???

I'm running a 350 Ironblock 5.7L Eldebrock Intake, currently a stock Ignition & Fuelsystem. with a 3inch single Cat. back Flowmaster Exahust system w/ chevy SS tips. 3pass High performance Radiator & all new cooling system. Nothing has been done to the original Drivetrain, But I already know what thats going to be.

[Trash man]

i assume u kno how to tune and burn chips for ur tbi? or know some1 who does. but do a nice 500ish lift cam somewhere in the 2X00-5500 band( should be real nice for cruising) also what heads are u running?

[OldSchoolGuy7]

i assume u kno how to tune and burn chips for ur tbi? or know some1 who does. but do a nice 500ish lift cam somewhere in the 2X00-5500 band( should be real nice for cruising) also what heads are u running?

I don't know anything about tuning or burning chips for the tbi, but I'm sure with more information I will definitally be looking into it. I'm running Vortec heads on a 350block (this is not an OE for this car, it was orig. a 305, the block came out of what I was told to be a 92-93 Chevy pickup), its been needing a valve job on it, so i figure'd why not do it all lol. I plan on doing as much work as i can myself. btw I have no clue what compression ratio's currently are.
**Crusing is exactly what I want out of the car, with some more pickup(accel), currently get 16mpg+ will be running a performance 700R4Tranny w/shift kit, Stall Converter, my main concern right now is the engine though.