hcbph

To me it looks like you either have to take the MAF off to get at it or move the a/c compressor and the emissions control over the compressor. You can see the IAC but you can't get to it without taking things off from what I can see.

Wish it was a 5 minute job but I don't see how.

Disregard the arrow in the picture, it was one I took for another repair done in the past so the arrow doesn't mean a thing in this instance.

81c3

So the way I did it was remove the intake tube, unplug all associated electrical connections, throttle & kick down cables, then remove the 4 bolts holdig in the TB. Take off the hoses that are not coolant related. I used a channel lock to get started on the removal of the IAC, then I used an adjustable wrench to get it off the rest of the way... About 35 minutes going slowly... 5 minutes is a stretch.

aklim

Sorry. I might be wrong since I have a 91 and it is SD so no MAF. Also my system isn't stock so some things might not be there.

mazdaverx7

When I removed the throttle body to clean it and check the IAC, I looked for ways to remove the IAC without taking the throttle body off and it seems that the quickest way was removing the throttle body. Took me about 5 minutes to remove it so no issues there. Every time I take it off though, it makes me want to do the preheater delete on the throttle body..ugh..

aklim

I don't think it is a useful item. Preventing freezing unless you are in the artic doesn't mean anything to me.

Pile_Driver

Just curious if the OP found a solution to the described symptoms. My 90 behaves exactly the same.

mazdaverx7

No, not at all. I replaced the IACV and it was acting a little better for a few minutes and then back to the same high idle crap. It makes driving the car unenjoyable at times and makes me feel like I should have either just bought the 84 that I first looked at or just waited and bought another LT1 car. I work on cars for a living and this is really baffling. The only thing I can think of is that the ecu is holding the throttle open for some reason or that the throttle body itself is bad. I don't have another good known throttle body to try or I would try that to eliminate that as a possible failure point. I haven't been driving the car very much because of this issue. I love the car but this just irritates me.

yd328

I have a GM1 connector for my mt2500, if it will work with your scanner you can borrow it to read the live data. I think the data would be helpful.

Gary

mazdaverx7

That would help out a ton! My Snap On scanner is older but its OBD 2 only. I don't think I have the OBD 1 adapter but I can check. I tried an Autel brand machine that a friend owns and used his OBD 1 adapter and it wouldn't read back to 86. 92 was the oldest that his machine would go.

yd328

It's easy to send it out to you. Iirc the solus and possibly modus can use the same adapters as the mt2500. I think if you can look at the iac, O2, and block learn, etc, together you may get a better picture of whats going on.

Gary

mazdaverx7

I think you're heading in the right direction with this. I have an older Solus scan tool. Live data will be the only way that I'm going to pin point what's going on.

mazdaverx7

I wanted to add, the issue is only present under load or more specifically after the car is driven a few miles. It will sit and idle perfectly all day long. You can rev the engine and the idle will always return to 700 rpm. Partly why I believe that the issue is electronic and the ecu is keeping the idle high with vacuum.

mazdaverx7

So, here's the odd thing. Now that the weather has dipped into the 60's and 50's in the morning, the idle has been great. Hangs at 1200 rpm for a second or two and then drop to 7-800 rpm. Odd that atmospheric temperature has an effect on the idle.

Cjunkie

Coolant temp sensor?

bosshog8

I had this issue which a faulty thermostat contributed a large part to.

mazdaverx7

I replaced both coolant temp sensors when I bought the car. The one for the gauge was dead so i also replaced the one for the ecu. It's possible the one for the ecu isn't working perfectly I suppose as the cooling fan does not always kick on. It does so when it wants when its above 229 degrees. Other times it doesnt at all. That could be the relay but i haven't dug into it much yet.

The engine temps stay fairly consistent and the heat is in working order. I assume the thermostat is ok but honestly I think I'll replace it before I put the car up for the year.

9T3VETTE

Next time you notice it pop the hood and check the throttle. If it is getting stuck you will be able to push it back and hear the RPM drop.

I chased a high idle for some time and this was the cause. Regular WD-40 takes care of it but need to figure out a long term solution now.

mazdaverx7

I was working on the Vette the other day and I decided to remove this little aftermarket piece in the throttle body. Some sort of air diffuser. I remember seeing them advertised as like a 10hp gain or something. I don't really buy it. Well, I removed it and the idle has settled down a bit. I can't drive the car due to the salty wet roads but just in the driveway it seems a little better and the idle isn't sticking or lingering. Can't wait for a dry day.

aklim

The key word is "UP TO" 10 HP. Anything from a negative gain to positive 10HP is technically accurate. IS it like an airfoil or what? Have you tried getting a scanner and not a code reader?

mazdaverx7

The airfoil that I removed was similar to that. I could care less about its claims to a power increase. I'm glad its out of there, lol. I have an nice Snap On OBDII scanner but I need the OBDI adapter. No current check engine lights and as of now it seems to be running well. Would be nice to be able to drive it to confirm but the weather isn't complying. Snowed more again last night. I'm really sick of this cold weather.