spiderhole

I was able to take a closer look at mechanically is going on with my carb to try and understand overall how it works. I wish I had a normal one to compare it to, but I have been reading this board plus the manual.

I took the below pictures today.

From an operating perspective here is was was going on: The car was sitting at about 1500 rpms once warmed up, it didn't want to kick any lower, but sometimes it would sit higher. I have determined there are no vaccum leaks.

I back the Fast Idle Air screw out, and that definitley brought the idle down to normal range; however, I now understand why the idle would something stick higher, and why when you goose it, it would fall back down. It seems that the assembly doesn't always want to fall all the way to the idle air screw and to the set idle. It hangs up about 1mm from hitting the screw which makes a big difference in the idle.

My problem is with this, all the springs seem good. Even when I push on the spring loaded device I have circled (farthest red circle on your screens right), it doesn't push the assembly up against the idle air screw. It seem like the front of the assemby where I have circled is loose (my finger is pointing slightly above it in the blue glove). It I either pull the throttle back and release it like I stepped on it and released it, it falls right into postition on the air screw at normal idle. I can accomplish the same thing by gently pushing it forward with my finger.

I tried some carb cleaner on the suspect areas and exersised it back and forth, but it didn't seem to help the overal problem. I'm not sure what the normal postion of the air screw is, so I'm not sure also if I might be going down the wrong path entirely.

Also, even at normal idle, it seems like its idling rough to me. The RPM's bounce around. I can't help but feel like this carb might just be better replaced or rebuilt.

I hope I have described the problems I am having clearly...

spiderhole

...I'm looking at the manual. Maybe I should try the Air Valve Return Spring Adjustment?

five7kid

iTrader: (14)

The air valve return spring has nothing to do with the idle speed. It controls the opening rate of the secondary air valve, which doesn't open until the secondary butterfly is open.

The rear "spring loaded device" in your first picture is spring loaded to allow the primaries to open when the secondary butterfly is "locked out" by the choke being less than fully open. It doesn't close the throttle, but if the linkage to that can be maladjusted and hang up.

The front "spring loaded device" is your primary throttle shaft. The green spring on the bottom of the throttle arm is the primary return spring, which is usually a double, which I can't tell from your picture. If it's a single, perhaps that's your problem.

Rough idle is either a lean mixture (most often a vacuum leak), a poor ignition system, or a mechanical problem such as low compression or improper valve operation.

spiderhole

It is a double spring

If there was a vaccum leak, where would you check first? I am wondering if some other mechnical part other than the carb is causing an issue. The hoses have all been replaced. Also, the plugs, dist cap, rotor, plug wires, and O2 sensor have also all been replaced. AC delco parts.

The engine has 60,000 miles on it, but the car had been parked since 1993. I'm actually surprised its running at all!

five7kid

iTrader: (14)

Mount gasket, and anything a vacuum hose goes to.

Remind me, have you already sprayed down what you can see with carb cleaner?

You might also have a sticking valve/lifter (although that wouldn't cause a high idle).

spiderhole

I have sprayed down the locations that seemed suspect to me with carb cleaner, and exersised them back and forth. It just seems like like it doesn't want to fall all the way onto the idle screw unless the throttle is pulled at least half way back and released.

When you say mount gasket, you do mean what the carb is actually sitting on correct? If the carb has to come off, I will try my hand at rebuilding it, slowly and correctly.

I might change the oil again and run some marvels through it. It worked wonders in another car we had sitting for a long period of time with similar issues.

spiderhole

Here's another question, sorry... I am wondering if there may be an improperly placed vaccum hose that I missed. I wonder if they are not routed 100% properly and that would do it.I think its setup correctly, but...

five7kid

iTrader: (14)

Check the vacuum diagram thread on the FAQ forum if your underhood diagram is missing.

Damon

The usual culprits of a high idle, aside from vacuum leaks, are:

1. Choke not opening fully and allowing the throttle to return all the way down to the curb idle screw. Bad choke element, inadequate voltage to choke element.

2. A/C compensator solenoid activated all the time. That little device in your 2nd picture.

3. Throttle cable sticking/binding. Temporarily disconnect at the the throttle arm to check this out.

4. Worn out primary throttle shaft bushings causing binding/sticking of the primary throttle arm.

spiderhole

you're in Philly huh?

In the picture, where my finger is pointing, that is the throttle shaft bushing correct? There is a lot of play there. Would it be possible, that not only it is sticking there, but also causing a leak, and potentially the rough idle?

If its any help also, all these pics were taken while the engine was running and warmed up.

I am going to dig into this again this weekend.

naf

iTrader: (7)

Possible, but if it's truly only got 60,000 miles on it, unlikely. I'd look for something sticking/gummed up-the kind of thing that can happen when mechanical parts sit for a long time without being used.

Do you have, or have access to, a dwell meter?

dirtywhiteZ28

I was looking real close at your pictures and noticed that the choke wire connector has the front part of plastic busted off. Thats a common place for those connectors to break, the weird part is that it may seem as though it is connected properly but as with my car you may be getting only intermittent power to the choke. If the choke isn't getting the power source it needs then it will never fully disengage the choke levers in the carb, leaving you with partial choke position on the throttle shaft. The idle will stay on the fast idle setting until you get enough electricity,for long enough time, to the choke element.A new choke connector should be available at autozone or oreillys for about $11 dollars. I would seriously consider fixing this before writting off the carb.

dirtywhiteZ28

Just to be clear, you were making these observations of the thottle shaft hanging up while the car was running, but with the A/C turned to the OFF position or the blue wire on the A/C idle compensator soleniod removed before starting the car????