SharkSkin

This is really interesting. I haven't touched my idle/mix screws since about March 2004, 22K miles + ago. Except when I messed with the idle speed to get the alt to charge. Here I am thinking this must be one of the most reliable all-mechanical fueling systems in mass production, and you're having fits. Have you re-sealed everything, including the dist. to plenum and the two plenum halves?

BTW BC, I meant to say something about this earlier, but fuel distributor has been untouched since Feb '04.

928BC

Dennis
I have tried to gap my plugs to both limits(w8dc) .028 - .032. Gapped to .032 they were clean as a wistle no color or nothing so I closed the gap back to .028 and some gray color was noticable. I 'll have to check poll 15.
Dave
BTW BC, I meant to say something about this earlier, but fuel distributor has been untouched since Feb '04
I was refereing to Hupp I was following one of his posts awhile back, and I think he changed his distributor.

hupp

I did change my fuel distributer and this made my shark dirveable --finally. I had chased down just about everything during this period - I was in denial that it was my distributer. I should add that since my distributer replacement the CIS has been much more robust and I have not needed to adjust as much. All of my recent adjustments were needed because I had been doing it all wrong in the past. Just trying to ween myself off of a bad habbit with the adjustment tools in the car.

BTW - I just got back from a good cruise on the interstate and she ran great (since my latest mixture adjustment). I adjusted to the rich side at idle the other night and all is good now when up and running. My idle is still a bit erratic. I can set it at spec (with shark at operating temp) and go for a drive and the idle will increase by about 200rpm, but sometimes it won't. My plenum is sealed good. I'm starting to suspect my 27 year old decel valve.

Chuck Schreiber

Hupp,

Yup. (did I make a ryme?) Same you hit it on the head. The idle FEELS smoothe, but the SOUND lopes every 10 seconds or so. Can't rember who said it "CIS cars like to be driven". I agree! The more I drive it, the better it runs. The car hates to sit, especially on my big 10-12month projects on the car.

I took it out last night in 50 degree weather and it ran like a bandit!!!! It loves to be driven, and driven in cool weather.

Would decel valve make revs coming down a bit bouncey? It revs good at a stop but coming down it initially comes down to 1100rpm bounces up slightly and then comes down to rest at 850rpm.
Sound like decel valve?

hupp

Chuck,

Sounds like the decel valve. Basis my understanding, the decel valve allows air to bypass the throttle plate, the amount of bypass depends on vacuum. This keeps your idle up a bit as you coast down and reduces the breaking effect. It stands to reason that a worn out decel valve can pass air erratically or pass too much air if not operating properly. Sometimes I can blip the throttle at a stop and the idle response will be pretty quick. Other times it is as you describe. I can rev to 3000rpm, release throttle and idle will drop to 1100rpm and then slowly drift back to 850rpm. Sometimes when the idle lands at 1100rpm a quick blip of the throttle will quickly return it to 850 rpm. Maybe this jars the vacuum diaphram if it is getting stuck.

SMTCapeCod

I replaced my decel valve and still have some symptoms being discussed. I'd check it out before springing for one. The Decel hoses, on the other hand, are cheap and should probably be replaced as P/M if they ahven't been...

My car was exhibiting the idle hanging earlier this year, too. Fixed it...not sure I remember which step in the littany of tuning took care of it. I wanna say that additional work with the mixture, leaning it and reducing the idle air screw adjustment did the trick. but I'm not certain. I've joined tamperers anonymous, recongizing my constant tinkering as a major threat to reliability..but the variabiility that makes it just a smidge not quite right, or at least erratic, from ttime to time is making me nutz too. Good think its time to park it for the winter I suppose.

Chuck Schreiber

Scott,

My car acts exactly as you describe.

Cape, I'll check vac lines as you describe, but pretty much everything in there has been replaced. This CIS Is all voodoo shee-hot isn't it??!!!

BTW, most of you talk about the little valve that hangs from the crossmember that has something to do with idle speed and having the AC on. I think mine is the only one I've seen that does not have this. Even the Euro motor I have next to my beer fridge has it. My wiring harness does not even have a provision for it. May be a later 79 feature?
My vin is 070 so pretty early in production. (Aug 78)

SharkSkin

Chuck, I have that supplementary air valve. Maybe someone clipped the harness?

BTW, I do note an occasional tendency for the idle to come down to maybe 1000 rpm rather than 850. It's probably the decel valve, but it happens so rarely I haven't been worrying myself about it.

Dennis Wilson

One other area to check if you are getting high initial idle is the tension on the throttle cable. I've heard of worn motor mounts settling and causing too much tension on the cable. This prevents the throttle plate from completely closing. BTW the adjustment is on the firewall.

Dennis

Chuck Schreiber

Do our motor mounts wear like the later ones? Thought they were pretty much indestructable.

Dennis Wilson

Chuck,

Haven't had the priviledge of changing mine, so I can't say. I did loosen mine but later found out the cruise control cable was sticking and holding the throttle open.

Dennis

SharkSkin

They don't collapse like the later ones, but they do come apart. On my car, both sides were like this:

Chuck Schreiber

Probably sure that mine are toast as well.