Hello.

Background: I have an -86 CCC LG4 that has undergone a few changes. I suspected that some of its flaws were due to the moldy old Quadrajet, so I got a remanufactured one.

After swapping, it got a 4000-5000 rpm idle, and the idle screw on the port side isn't even touching anything.

I have had problems before with high idle more or less randomly. At times it would be 2500-3000, when I stopped the engine and started it again and it would be 600 sometimes and keep at 2500-3000 others. I suspected this was because the Q-Jet was old and I received computer failcodes about the mixture solenoid being broken and whatnot. Now with the new carb, the problem got WORSE.

I wish I knew what all those devices on the carb really do. If I poke some lever on the starboard side the primary valves stuck in different positions. If I yank the throttle they go back to closed. When I start the engine the primaries open fully - more so than I can open them by merely pulling the throttle. I'm mightily confused.

And I'm a bit at loss for solutions here. Should I expect one remanufactured carburetor to be well adjusted from the start, so the problem probably lies in my vacuum lines or something? Or are there steps I ought to know on how to adjust a new carb to a new car or such?

It is fully possible that the vacuum lines are out of whack, because me and some friends swapped cylinder heads and manifold and exhaust and got rid of the A.I.R and A/C, and none of us were any experts.

you want all the blades closed for it to idle not wide open.

Really? =/

Because when I tried poking at the carb until the blades closed, then tried to start the engine, it was stone dead until I mashed the gas pedal and held it to the floor. Then it would start and immediately creep up to redline, and when I went out to have a look the primary blades were wide open.

When I then poked once again at the carb to make it close, the engine would just die.

This is part of my confusion. The blades have two or three steps where they like to rest if I yank the levers a bit - almost closed (I thought this was the idle position), full open (release when pulling the throttle) and perhaps something in between, I don't quite remember.

Also, I see no difference in this behaviour whether I have the choke cable attached or not.

The blades on top of the primaries are/is the choke blade. When cold it should be nearly completely closed prior to start, then once the engine starts running, vacuum to the choke pull-off (canister thing in front) will open them slightly ('bout a 1/4 inch). As the electric coil in the choke heats up (12V wire goes to it) the choke blades will gradually open until they are fully 90 degrees straight up. Once the choke is open, the throttle can be pressed down and the high idle cam will release and idle speed will be controlled by the curb idle adjustment under the throttle cable connection.

A reman carb will likely need some adjustment to the Idle Air Bleed for your application. A dwell meter is handy. Sticky on top of this forum describes in detail a lot of these pieces/parts.

> The blades on top of the primaries are/is the choke blade.

*Slaps forehead* Why, OF COURSE! >_<

Please pretend that you never read any of my idiotic musings about those blades, and thank you sincerely for cleaning up a hefty amount of my confusion!

> A reman carb will likely need some adjustment to the Idle Air Bleed for your
> application.

Sincere thanks again, this is the kind of information I really needed. For all I knew, the carb could have had one size fits all factory settings and any turning of any screws might ruin it.

I take it you refer to the scanned E4ME & E4MC CARBURETOR docs, page 6C1-12?

Yeah and there's an old thread started by Nate86 on rebuilding the carb that added some hints/pointers. If you get stuck just post.

No, this can't be right.

I'm reading the docs in that permalink and from the looks of it, I am supposed to tear down the carb and adjust it in several spots, most requiring special tools because they are not to be tampered with.

Some are even missing from my carb, I can't make sense of it. I mean, "Idle Speed Control" sounds like it would be a mandatory component but there is nothing like it on mine. Is that only for auto gearboxes? Mine is a manual.

Got to be something simpler awry. I suspect vacuum, because I had similar problems to this before, only not as severe.

Yours shouldn't have the idle speed control motor. It may have an electric solenoid that functions similarly to the idle load compensator.

Your re-man carb is likely set to proper specs for the rich and lean stop, although it wouldn't hurt to verify 1/8" of travel for the MC solenoid. Proper adjustment procedures from there(for me anyway):

Set base timing with EST disconnected. 0-4 degrees, maybe six, your choice. Older engines with carbon buildup may not tolerate as much timing.

With idle mixture screws and Idle Air Bleed 'in the ballpark' at 3 turns out each (all three) set curb idle.

At curb idle adjust TPS to get ~0.40 volts at idle.

With dwell meter, adjust IAB out until dwell 'hovers' at 30 degrees or 50%. If you go to 7 turns out on IAB you need to start back with 1/2 turn out on the idle mixture screws.

If curb idle setting changes re-check TPS voltage.

Special tools required: Dwell meter, idle mixture screw tool (forget the name and you may not need this-I'd try adjusting just the IAB before purchasing this) and small roll-pin for TPS adjustment tool-just lightly tap it on.

If you're concerned about possible vacuum leaks, plug every port on the carb and manifold except the vac sensor, adjust the carb to get proper dwell, then re-connect each line. If you re-connect a leaking line the dwell will respond by richening the mixture.

Superb instructions, thank you!

Okay, now I know more. The idle is fine, but the fast idle cam plays tricks.

When I poke that lever thingamagig on the choke side, the choke blades open up and the idle is a steady 800 rpm or so.

When I pull the throttle linkage, there is a click, that lever jumps up again, the choke blades close up a bit and the revs increase to 4000-5000.

When I push down the lever again, the blades open wide and the idle goes back to where it should be again.

All the while, I have 13.3 V on the choke wire connected to the carb. Disconnecting that wire makes no difference. There is no choke light on in the instruments, though I have seen it light up once or twice before. The engine was cold to almost-warm during this, I had it idling for at least ten minutes.

What do I do about this? Tie down the lever with wire?

When the engine is cold the choke blade should be held closed by the coil inside the choke cover. You should be able to poke it open and it should spring back closed.

Fast idle is set when the engine is cold by depressing the throttle prior to starting. This will bring the throttle stop up off the curb idle set screw and allow the fast idle cam to hold it open.

With the engine first started you should be able to see the choke blade slowly open over about 5 min or so. Once the choke opens the fast idle cam will stay in place (high idle) until the throttle is opened and the cam falls allowing the idle to drop (rest on curb idle stop).

Choke closed: fast idle cam engages when throttle is opened

Choke open: fast idle cam drops when throttle is opened

Choke opens as coil is heated with 12 v.

Is this what is happening?

I appreciate your very distinct directions, thank you!

As it seems, I have 12V on the coil, still the fast idle cam engages when throttle is opened. This also happens with the choke cable pulled off.

The first time I started the engine yesterday, I pumped the gas pedal a few times as I turned the key. I know people say not to do this, but my old worn-out carb absolutely needed it with a cold engine so it is a bad habit.

But the second time I started the engine I made a point out of not touching the pedal because I did not want it to stuck in high idle, yet it behaved the same.

Anyway, I might be confusing things and it could well be the case that the carb is doing what it should, it's only that once fast idle kicks in it goes to way above 4000 rpm. If only it were 2000 or some such it would be fine.

I do have modified the engine with new cylinder heads, headers and intake manifold. Could this affect the response at fast idle so much?

I see here that there is a screw for adjusting the fast idle!

http://www.jetchip.com/carbtechinfo.asp

I'll see if that improves things.

Yes, determining that the choke and fast idle system is operating correctly is difficult to do across a key board. You may want to ensure everything is freely moving and compare what you've got to the diagrams in the sticky.

Adjusting the fast idle and choke should be done after the other basic adjustments are complete. A rich condition can cause a bump in fast idle.

A common failure point in this system is the choke pull-off. It can be checked by removing the vacuum line, depressing the plunger then holding your finger over the vacuum nipple connection. The plunger should remain depressed until you remove your finger. Probably not your problem but it should be checked before any choke adjustments are done.

What do you mean "choke cable pulled off?" Do you mean the 12 volt wire?

If the choke thermostat has 12 volts (how did you verify this?), and the choke doesn't open within 5 minutes or so, the thermostat is shot. If you took the 12 volt wire off, then the choke will never fully open. All the 12 volts does is warm up the thermostat coil - the coil does the actually opening of the choke (or, to put it another way, no longer closes the choke).

The high idle speed should be adjusted to 2200 RPMs with the engine warm. You do this by warming up the engine, opening the throttle a little and simultaneously pulling the high idle cam (green weight) up, then adjusting the high idle speed. If it's going to 5000 RPMs now (a little hard to believe, but possible, I suppose), back off on the high idle adjustment screw before trying this.

The choke pull-off (vacuum break, in the GM vernacular), is only a small player in high idle speed (basically drops the high idle cam down one notch). But, it is a vital part in the overall smooth operation of the choke.

As I've said in other threads, these carbs work amazingly well when all of the parts are given a chance to do their thing and everything is properly adjusted.

Those are good pictures from Jet, by the way. I've bookmarked them. They don't show the IAB and TPS adjustments, but we can cover that. Hopefully nobody will ask where the "APT" is on their CC q-jet. . .

Just got back from poking around with the car more.

Had to help it start with the pedal. The engine immediately rose to 4000 rpm. I got out and pressed the lever and it lowered to 7-800.

Screwed out the fast idle screw a bit and pulled the throttle. Revs rose to about 2000. Poked the lever again. Let it idle for a few minutes while moving stuff around the garage.

Put the air cleaner back on and went for a drive. Burbling out in the street, not pushing the gas much. Got to a road, put it in third gear and floored it. Car gargles away as it should, but then the idle is suddenly 3000+.

Stopped at a gas station and screwed the fast idle screw out more. And more and more until the idle settled on some 1500 rpm, it would not go lower.

Went back home, and the engine is certainly warm now, but it still insists on idling at 1500-2000. I'm too tired to care more now, locked up and went home.

I did think it smelled like gasoline in the garage. Perhaps the mixture is too rich after all. I will check dwell when I get hold of a meter and learn how to do it.

Ignition is set to default 0° as printed on the label on the hood.

If you can get it to idle properly by manually releasing the fast idle cam and getting the throttle to rest on the curb idle set screw-you've got a problem with the choke and/or fast idle cam assembly.

Idle should not be resting on fast idle cam or controlled by fast idle set screw with the engine warm and the CHOKE BLADES AT 90 DEGREES STRAIGHT UP.

That's what we've been trying to say!

You've got a problem with the choke thermostat.

How did you verify you're getting 12 volts to the choke thermostat?
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I copied this picture from your other thread into this one.

Is that what your choke thermostat looks like now? If so, there is no 12 volt wire on your choke thermostat. Until you get that hooked up, no way no how is your choke going to operate correctly.

If that is your oldy moldy carb, and you've got the wire hooked up now - never mind. . .

never mind about the gas line being bent - other thread already got it

Right, just the missing 12 volt wire from the thermostat housing.

That is my old carb. I put a new rebuilt on the other day. The old carb also had the high idle/poke the lever to decrease it problem, but in a much less scale.

There is 13.3 V or so on the blue cable going to that connector. I measured it with a multimeter.

The choke light came on the other day, but has been off since. I'm not sure I even need a choke function on this car, given a little encouragement with the pedal it starts fine and idles steadily (when not on fast idle) right away.

This car has not been well kept and has several other problems, it was a mess when I first obtained it so it would not surprise me if sensors and whatnot are wrecked or cables put on wrong.

You'll be much happier with a properly operating choke.

Is the SES light coming on?

Say - what has the oil pressure switch to do with the choke, really?

The reason I am asking is because I am reading the carburetor manual that is linked in the stickies.

On page 6C1-2 it says a at the bottom of the left column:

"3. If the choke blade fails to open fully within 3.5 minutes, proceed to steps 4 and 5 below.

4. Check the voltage at the choke heater, blah blah
a. Blah blah
b. Blah blah. If any connections in the oil pressure switch circuitry are faulty, or if pressure switch is failed open, the oil warning light will be on with the engine running. Repair wires or connectors as required

5. If steps 4a and 4b do not correct the problem, replace oil pressure switch. No gasket is used between the choke cover and the choke housing due to grounding requirements."

My oil pressure switch (?) is broken. My oil pressure meter has been indicating an oil pressure of like a million psi, even with the engine off, and this has been the case for a long time.

Clearly, this is bogus because the engine has been running for a thousand miles with "infinitely high" oil pressure, and I have been ignoring it all the while (well, I did replace that cylinder with the cable, near the distributor on the rear of the intake manifold, but there was no change).

I had other weird problems with the dashboard due to shortings and burned lightbulbs, so I figure the oil pressure was a shorting there and nothing to worry about.

But now it seems that it may for some crazy reason be connected to my choke problems?

After I changed the carburetor, the oil pressure needle has begun slamming into the bottom instead.

Why on Earth would oil pressure be related to choke operation?

Apparently some qjet vehicles pull 12 volts through an oil pressure switch to the choke. They do this so that the choke only gets power when the engine is running-so it's not opening while the key is on/engine off.

Your vehicle should get power through an alternator lead, basically no power unless the alternator is turning AND generating electricity. Alternator doesn't turn when engine isn't running-same effect.

Should be no connection between your oil pressure SENDER and the choke operation.

Car seems to have mended itself during the last weeks. Today it ran as fine as I could wish for.

The idle was good on cold start, after driving a couple of minutes it was somewhat high, but after a stop and restart it was as good as I could ask for.

I guess the ECM runs Windows 95 and needs to be rebooted frequently to work.

The ECM does not command your idle speed, it sounds like you have some sticky choke linkage.

Yes, I think the choke is engaged for far too long. And the carburetor is a "brand new" (renovated) thing.

No matter how much I poke around with that choke-side linkage, I can't wrap my head around how it works. There are springs and linkages and leaf levers and vacuum clocks and cams and whatnot operating with and against each other according to no logic I can grasp.

Which bugs me to no end since I am a mech eng myself and ought to be the first one in any one crowd to figure such things out. >_< I would disassemble the old carb to learn from it weren't it for the fact that it is horribly mutilated and lacking most components on the choke side. Someone else also had problems it seems and took the rough solution.

Choke action in simple terms (and risk of oversimplification):

The choke blade is held closed by a bi-metal coil inside the choke cover. As the coil is heated by the 12V wire connected to it, it slowly uncoils and opens the choke. The coil is connected to a lever that moves the rod you see attached to the choke blade.

Throttle is held on fast idle stop when the choke blade is closed. The throttle has to be opened enough to allow the fast idle cam to swing into position while choke is cold. This is why your cold weather starting procedures call for a few pumps of the gas (also to provide a booster fuel shot into carb). When the choke opens the fast idle cam will fall away when the throttle is lifted off of it, it has a little counter weight on the opposite side. If the throttle is not lifted off the cam (gas pedal pushed) it will sit on the fast idle cam even after the choke is completely open.

The choke pull-off is operated by vacuum and is designed to crack open the choke blade a small amount once the engine starts running (and provides the required vacuum). Choke blades completely closed allow the engine to start in cold weather but the blades need to be open slightly to keep it running.

There's additional linkage that connects to the secondary air valves. The choke pull-off will delay the secondary valve opening slightly when the throttle is wide open and it loses vacuum. This operation is independent of choke coil/blade position.

Most of this may have be old hat for you now, but knowing what it's supposed to do may help figure out how it does it, which is much more difficult to explain.

Thanks a lot, that makes sense. I was staring incredulously at the linkage to the secondaries wondering what the heck it was for.

I went for a drive today - it's kind of weird to be able to drive a Camaro with summer tires in Sweden the 30th of December considering that we are at the latitude of Alaska, but there is no snow or ice yet - and the car ran as well as I could ask for from an abused old rustbucket such as this.

The idle was a high 1500 or so when I came back to the garage, so somewhat annoyed I snapped off the aircleaner expecting to be able to poke that lever to open the choke valve.

The choke was disengaged, the fast idle not engaged, it was the curb idle screw that held the idle so high...

So all in all, I think my carb works as it is supposed to, it's only a bit slow (10+ min) in closing the choke. The choke cable does have 13+ V on it when I measured though.

I now remove the carburetor from my To Do list and thank you for your guidance!

maybe the electric choke itself has too much resistance? damon posted how to check that on 19 Nov on this post: https://www.thirdgen.org/forums/carb...nd#post3538271

Most interesting, I shall look it up. Thanks!