87 Chevy TBI IAC Troubleshooting

[87ChevyV20]

I got the new throttle body base yesterday and installed it just now.

Runs like a dream!

I do have one problem though, It seems the throttle return springs aren't strong enough, or maybe the butterflies aren't closing all the way because Blister is still idling high.
If I close the butterflies from under the hood, the RPM's go to where they need to be.

Has anyone seen this and maybe has a fix?
Or maybe it just needs to wear in for a bit?

 

[YakkoWarner]

Sounds like you just need a stiffer spring since you can manually pull it back. I put a secondary return spring on mine because I know its worn and sometimes wouldn't close all the way back down when lifting off the pedal...last thing I want is a 454 stuck partially open when I need to stop.

 

[87ChevyV20]

I'm kinda wondering if this was the problem with the old base I had, other than the stuck idle screw.

Maybe it could be a cable or something.

 

[Sgt Gus]

I'm kinda wondering if this was the problem with the old base I had, other than the stuck idle screw.

Maybe it could be a cable or something.

Check with your source that you got the throttle body from. They may have the proper spring. Ours closes no problem, only time it wouldn't quite, is if throttle cable is too tight.
Let me know if you need resources.

 

[87ChevyV20]

I bought it from a rando on Ebay, so I don't think there is anymore info to be had.
It came with springs and they feel about the same to the old ones.

I have verified that the cable is not the issue.

The blades are definitely staying open a bit.

I can hear the butterflies rubbing in the bore, so I am wondering if I need to adjust them.
I would have to pull the throttle body out again though.

Here is the throttle body base I got.

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[Sgt Gus]

Hmm, so blades are sticking open a bit...are they hitting? Like before you installed did they do that? Did you clean up with something, it looks dirty...

 

[87ChevyV20]

I did clean it up, but I didn't think to adjust the butterflies.

 

[Sgt Gus]

Well I'm of no use. I haven't had to adjust one.
It looks a little different than our 454 tbi. Is it a rochester 200?
I also want to direct text you about the aldl cable and tuner pro. I have the cable and TP, but no files

 

[87ChevyV20]

Not really sure, but it is a Rochester. Here is the part number.

You must be registered for see images attach

Message me any time.
I am a noob at the ALDL stuff, but I did get it working.

 

[Sgt Gus]

Sorry, Rochester TBI 220, looks like they may have bent the back vacuum port for MAP sensor to access an adjustable fuel pressure regulator.

 

[87ChevyV20]

I think that is factory, the old one was like that.

I think it is to clear the fuel fittings.

 

[Sgt Gus]

CU-TMC? Must be different for a V20 vs a R20, 1987?
https://www.carburetion.com/CarbNumber.asp?Number=17090061

 

[87ChevyV20]

I don't think that is the one, mine has 4 vacuum ports on the front.

 

[Sgt Gus]

You figure out issue? I can send pics of ours.
I asked a refurbisher about yours. No adjustment other than throttle cable or idle screw.
If you have shaft play, it may just need to be rebuilt.

 

[87ChevyV20]

No, I haven't messed with it.
Rained yesterday and today is pretty windy and miserable out.

There is adjustment in the butterflies on the shaft, I checked it with the old one.