Welcome to the Corvette Forums at the Corvette Action Center!

1984 HI spped idle


Motor head!!!!
Feb 13, 2001
Valencia, CA,USA
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
1984 HI speed idle

OK helpin a bud on this one.

ALL his vac lines are SHOT... here were the series of problems.

22 Throttle position sensor
33 MAP sensor
44 Lean Mix

We changed the TPS ( and adjusted to .54 volts)
Changed the MAP.

Disconnected the battery ( while doing this )

It got the same codes. I chased the wiring to the ECM and it was correct...but the ECM was a weird aftermarket one... I saved my old good one from my 84 and now all the codes are gone....... BUT

The car would not idle worth a damn.( It didn't when I got it)

We cleaned the IAC valves and they were COATED with oil blow by. 117K HARD MILES ON THE CAR.

Reconnected the battery, and the car started to run normal then the idle crept up to 1100 and will not go back down.

I looked at the EGR solonoid and the wires were just taped on ( connector shot)

He's replacing that item today.

Question #1
ANybody have a good VAC diagram on this car.
Question 2
The EGR should not be working at Idle correct?
When does it kick in...2K and above, or just off idle.

Hi there,
Yes, you should not have EGR function, and if you did, you would be rough idling, or stalling, so you can basically rule out the EGR.
As for the idlling high, I would start with a throttle body synchronization. This is always the first course of action.
Then, I would look at the IAC counts, to confirm approx 20-30.
If all these are in specs, then I would seek out a sticking IAC motor, or a IAC that has lost contact on either end of the homing stroke.
Let us know what you have, and we can continue.
Besttoyou, c4c5:hb
Right Side IAC motor

Was stuck.....
I put one in ( just to block the air hole ) and connected the old one to the harness to watch it move...It didn't, found a good replacement and another good scrubbing/cleaning, a few more vac lines and 1 plug wire
(one caught on fire while we were working on it, laying on the exhaust) and it's running like a top.

Now the owner is going around and making big fix it lists... polishing everything in sight. This car has a LONG way to go ( 1 step away from pick your part) And this car has been VERY abused.. however it is cool that he is now making restitution to his Ol' ride.

Thanks again


Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors


MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Advertise with the Corvette Action Center!

Double Your Chances!

Our Partners

Top Bottom