sharkface
Jun 6, 2018
122
111
VetteCoins
1,736
Car
1985 Corvette
Hello, My Friends in Canada. I Am thinking of changing out the IAC (Idle Air Control Valve). Do you think the throttle body needs to be removed? 1985 Tuned Port Injection. I've seen it done on newer C4s without removing the throttle body.
I don't know if I'm being lazy or smart. Anyway, I ordered a new throttle body gasket and already have the Delco IAV valve.

My car runs so great with 100k except for the idle issue. Now it sounds like it has a racing Cam at idle. Tach goes from 500 rpm to 700 rpm to 300, and almost stalls. Does this both hot or cold.

Improvements I've done recently: 1. Coolant throttle body by pass. (Keeps hot coolant out of throttle body)
2. Air Foil, (an aluminum butterfly looking adaptor to the front of the throttle body
3. K and N intake plate cover for air filter. (Replaces the blinds with windows)

These simple fixes added noticeable torque.

Take Care,

Shark face
 
Hello, My Friends in Canada. I Am thinking of changing out the IAC (Idle Air Control Valve). Do you think the throttle body needs to be removed? 1985 Tuned Port Injection. I've seen it done on newer C4s without removing the throttle body.
I don't know if I'm being lazy or smart. Anyway, I ordered a new throttle body gasket and already have the Delco IAV valve.

My car runs so great with 100k except for the idle issue. Now it sounds like it has a racing Cam at idle. Tach goes from 500 rpm to 700 rpm to 300, and almost stalls. Does this both hot or cold.

Improvements I've done recently: 1. Coolant throttle body by pass. (Keeps hot coolant out of throttle body)
2. Air Foil, (an aluminum butterfly looking adaptor to the front of the throttle body
3. K and N intake plate cover for air filter. (Replaces the blinds with windows)

These simple fixes added noticeable torque.

Take Care,

Shark face
I googled it, 1st video shows it on the side of the throttle body, only removal was the air duct. Famous last words... it should be simple.... good luck.
 
Hello, My Friends in Canada. I Am thinking of changing out the IAC (Idle Air Control Valve). Do you think the throttle body needs to be removed? 1985 Tuned Port Injection. I've seen it done on newer C4s without removing the throttle body.
I don't know if I'm being lazy or smart. Anyway, I ordered a new throttle body gasket and already have the Delco IAV valve.

My car runs so great with 100k except for the idle issue. Now it sounds like it has a racing Cam at idle. Tach goes from 500 rpm to 700 rpm to 300, and almost stalls. Does this both hot or cold.

Improvements I've done recently: 1. Coolant throttle body by pass. (Keeps hot coolant out of throttle body)
2. Air Foil, (an aluminum butterfly looking adaptor to the front of the throttle body
3. K and N intake plate cover for air filter. (Replaces the blinds with windows)

These simple fixes added noticeable torque.

Take Care,

Shark face


assume this is an 85?

is it an automatic or a manual?

if its an auto, have you done anything with the prom chip in the computer?

have you performed the “minimum idle adjustment” with the min idle rpm set to 550?

if you can answer those i can give advice on how to acieve a perfect 85 idle…especially if its an auto. Cheers
 
assume this is an 85?

is it an automatic or a manual?

if its an auto, have you done anything with the prom chip in the computer?

have you performed the “minimum idle adjustment” with the min idle rpm set to 550?

if you can answer those i can give advice on how to acieve a perfect 85 idle…especially if its an auto. Cheers
Hello, thank u for the reply, C4 is a 4 sp Doug Nash with elec overdrive for 2nd, 3rd, and 4th

I talk about it on you tube
www.youtube. com
linkedup@linkedup7346
 
Hello, thank u for the reply, C4 is a 4 sp Doug Nash with elec overdrive for 2nd, 3rd, and 4th

I talk about it on you tube
www.youtube. com
linkedup@linkedup7346
in that case, simply carry out the minimum idle adjustment you can find the procedure by googling.

if the car still cannot control its idle (be sure to use 550rpm base idle) then you have extra air getting in.

85 can maintain its idle, but, it can take it a bit more time to get control of it than 86+

If you find it is just impossibly to dial in, closely inspect the throttle body plate hinge for movement/ovaling of the hinge pin.
 
ill add this if any other ccf 85 owners with an automatic trans find this.

obtain an hlh3200 chip. it is a gm chip, released late late late 85 to solve several issues in the auto version. You will not believe the difference.

you may need to obtain the hlh3200 bin file from tunerpro definitions and have it burned for you.
 
Hello and Happy Holidays,
Thank you for your replies to the removal of the Idle Air Control unit. I did have to remove the throttle body just to get enough torque on the old one to remove it. With the new one installed, my car idles at 900 and is very consistent. No more Roving Idle, The overall performance has also been improved.
Sharkface
 
OK but 900 is far from the correct idle. Its good that it has leveled out but its not right. commanded idle will be 700. unless you have had a chip installed.

this implies that, either you have vacuum leak or you need to carry out the minimum idle adjustment procedure on your car. Did you do this?

It is also very probable that you have both conditions. A small leak AND the min idle is out of adjustment. Most older cars that have not been completely gone through have both.

Question: Do all your hvac functions work?
 

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