Tampa 928s

78 cis
Doing some troubleshooting on my 78; throttle plate is not closing completely flat there is plenty of slack on the cable. Pretty hard to reach without the intakes off where do I adjust this to get the plate completely flat?
The throttle bypass valve is working although when completely warm I can see a little small triangle visible allowing air through on the right side should this not be completely closed?

LT Texan

There is no adjustment like on a carb to open the plate for idle adjustment.

It is designed simply to close until it is completely shut.

Tampa 928s

I am most interested in the acv if it is supposed to be completely closed when warm. That 1/2 moon cut out still shows and either this is used for normal idle as a bypass or it is not closing fully therefor raising my idle when warm.
Has anyone looked inside acv and found the same opening when hot? There is a pin that can adjust the disk but do not want to modify anything until I am sure.

LT Texan

ACV?

The aux air valve should shut completely.

The throttle bypass valve is used to adjust idle.

Tampa 928s

Been chasing a warm-up fast idle Wur is with in specs and trying to find a cause. With Cis and air not designed to be there throws the whole thing off.

The manual refers to it as an throttle bypass valve it is an open closed valve controlled by 12v and heat. I have read it needs to have a small amount of air passing through to provide an on throttle idle but only one source referenced this. I need to make sure that it needs to be completely closed in the 78 Cis before I start messing with it. Closed is what it is supposed to do but cannot take it at face value. Looking for someone with the same set-up that actually observed this by looking at it. I know sometimes closed is not closed, closed may mean end of travel with this tiny exception of the 1/2 moon providing an air pathway.

LT Texan

what year?

(On mine) there is an aux air valve to increase the cold idle. It is controlled by 12v.

And there is a throttle bypass valve to adjust warm idle. It is controlled by a screw.

Tampa 928s

78: See first post hopefully someone can clear this up for me. I have a good understanding of the Cis system but need this ? answered so I can get things back together. Everything else seems to be within specs.

LT Texan

Post #2. The throttle plate is designed to fully close. There is no adjustment.

Post #4. The Auxillary Air Valve should close completely when fully warmed by the 12volts.

Good luck

Tampa 928s

78 Cis
Well so far I have had two saying AAV closes all the way and two saying the small u opening remains visible when warm. Sounds like politics everyone has an opinion but where are the facts😣
100 views and no one ever checked this out before?

LT Texan

why don't you start a poll?

Tampa 928s

No pole needed I found the answer😃
After 10 min it closes completely so now how to repair it comes next.

LT Texan

Unbelievable.

Why don't you not waste our time and just go right to you tube next time.

Vilhuer

Except bolt at center of the plate which positions it to opening in casting. Plate needs to be set just right or casting will stop it closing completely. WSM has instructions how to do it.

LT Texan

Yes, it is designed to fully close when assembled properly.