OK, I swapped a Holley-rebuilt Q-jet into my LG4 T/A (manual trans) on Sunday night. It was running ok, albeit the fast idle seemed really high ~2500-3000 rpm. I took it for a test drive on Monday, and it seemed to run alright. However, later in the day, I started it again, same high idle, but when i step on the gas, the idle drops between 500-1000 rpm, and eventually dies.

I tried messing with the fast idle adjustment this morning, and was able to get that down to ~1800 rpm, and it was idling a little over 1000 rpm once I stepped on the gas pedal. I drove it around the block several times, and it was ok.

But, I just tried the car again a few minutes ago, and I am getting the same problem, where once I step on the gas pedal, the rpms drop so low the engine stalls. Can somebody please help me with this? I cannot find a clear cut answer to my problem in my Chiltons or Haynes manuals...



BTW, this is my first post so hello to everyone on thirdgen.org!

 

Welcome to the board!

The fast idle is supposed to keep the rpms up until the choke is warmed up, and once warmed up it'll disengage when you tap the gas. I know with my car its not quite warmed up at that point and will idle a little low and almost die when trying to drive away. After a few minutes of driving its fine.

Sounds like its working, but check that the blade above the primaries is fully vertical after its warm. Also check that the valve in the intake filter assembly is closed (pulls air of exhaust manifold) on a cold start and eventually opens.

 

Thanks for the reply. I let the car cool off all day, and started it earlier this evening... It fast idled at the speed I had set it to this morning, so I think I have that problem taken care of. And yes, the blades above the primaries are fully vert when warm, but i think the valve in the air cleaner never closes on mine - is that a problem?

But, I think it has another problem where it is hard to start the engine once it's already warmed up, because it seems to start up fine and idle decently on a cold start, but is difficult to start, and idles badly (often times too low resulting in a stall) when warm. Any ideas whats up with that?

 

I don't think the air valve not closing is a big problem, but definetly helps in the winter. Its only closed during a cold start it opens once warmed up.

Regarding the new problem you might have to adjust the idle higher using the set screw on the other side of the carb. How does it idle when its been running for awhile?

Wouldn't hurt to look at a couple of plugs just to see how the A/F mixture is.

 

It idles poorly once its warmed up (often it drops down so low it dies)- my new thread has that problem... It is hard to start and mostly dies right away when its warm.


Is the set screw the one which touches where the throttle cable hooks up? I was thinking of messing with that, but decided not to since I am unsure of what its true function is, and I wanted to wait for advice from the boards first. If that's the screw you're talking about, I will mess with it once I get a reply. Thanks again trumps!

 

Yea thats the screw that sets the idle normally. Set that and see how it runs.

 

I just found this thread, and I have an idle issue due to no choke assembly on my carb. I am going to install another E4ME that I bought...which has the choke assembly.

But right now, even when my car is warmed up it idles at 1500rpm - Even if I adjust the idle set screw. I am wondering if that could be due to having no choke or what.

 

Hard to say, I would think it should work fine after its warmed up but if the choke is missing who know what else is missing. A high idle could be caused by a vacuum leak.

 

There are two nipples on the front of the carb for vacuum. I know one is for the air cleaner. What is the other one for?? The choke?

Because there is no line coming off of that 2nd nipple.

Also...on a cold start, I have to pump the gas a few times after it's started to get it to fully rev up. After that, it pretty much idles at 1500 on its own....yes, without a choke. I found that weird.

If it is a vacuum leak, could it be from that 2nd nipple on the carb? Would that cause it?

 

The vacuum tap that the air cleaner TAC switch connects to should be tee-d. The portion of the tap that tee's off takes a hose to the vacuum pull-off that works with both the choke and secondary air valve. Do you have a vacuum pull-off installed?

Hope this helps.

 

Will you explain what the TAC switch is? Is it the piece that is inside the air cleaner...two vacuum hoses plug into it, then one vacuum hose goes to the nipple on the carb?

And how should the hoses be tee'd? Because there is only one nipple left after I plug in the air cleaner....and the nipples form kind of an L shape.

There is a T for the air cleaner hoses....one goes from one side of the air cleaner and connects the other....and then a single hose goes to the little piece inside the air cleaner, then it goes to the carb.

So I have no idea what other T you're talking about. And no, I don't have a choke pulloff...there is no part of the choke assembly at all.

 

Or did you mean that the hose comes off of the nipple on the carb, then T's off and one part goes to the front of the choke assembly (front vacuum break) and one part goes to the back of the choke assembly (rear vacuum break)???

 

The "tee" is what you're calling the "L shaped" nipple. The "L" part of the nipple goes to the vacuum pull/break. The vacuum pull/break serves two purposes: to pull-off the choke and help control the opening/closing rate of the secondary air valve.

TAC stands for Thermal Air Cleaner. It is the small vacuum switch inside the air cleaner that controls the door in the snorkel to facilitate warm-up. If you have the factory dual snorkel air cleaner there will be a tee after the vacuum switch with hoses to the door motor of each snorkel.

Hope this helps.

 

I know there is a flap on the drivers side, in the air cleaner and there is a hose type thing that goes from the exhaust manifold to that flap.

I do not have the snorkel hoses, but I have the dual snorkel system. I know there is a vacuum line that goes into the air cleaner and I guess it goes into a switch...it is a small square piece. Then another hose comes out of it, and I assume plugs into the "T" on the carb.

So the other part of the "T" goes to the choke pulloff? Located where? On the front of the choke?

Would not having the vacuum line going to the choke serve as a big enough vacuum leak to make the idle high??

 

I messed with the set screw last night, and was able to successfully drive my T/A to and from work today. I think I may have turned it a little too much since its idling ~1500 rpm, but I'd much rather have that than have it dying out under 1000. Thanks for all your help!

 

84z
The choke pulloff is a vacuum servo bolted right above and to the left of the T. Any vacuum leak can be enough to cause a high idle. Fix it and see how it runs. What I did when I first got my car running was to buy a bunch of vacuum plug caps at the local auto parts store and plug everything except the PCV and the MAP sensor ports. That should rule out most vacuum leaks.

jordezzy
You should be able to idle your car below 1000 rpm no problem if its stock. Did you try to get it to idle @ 500-750 rpm? If so what happened?

 

I changed out the carburetor for a rebuilt Quadrajet E4ME which has a choke.

When I start the car, the butterfly for the choke is closed, and it will eventually open up but not fully vertical...it will be cocked to the side some.

What do I do to adjust that??

Also, which is the fast idle screw? The one on top of the choke pulloff? Because I couldn't get my idle to go below 2000 when it was warming up.

And one other thing...I heard that there is supposed to be some kind of wire that connects somewhere on the choke heater or something....where is that wire supposed to go exactly and what does it look like? Maybe that is causing my problem.....or actually that shouldn't cause the fast idle problem, should it? But nonetheless, I don't have that wire hooked up and I don't know what the wire looks like or anything.

 

OK...I found the choke heater wire. I checked to make sure it was 12v and it fit perfectly onto the metal piece on the choke.

There's only one thing though....when I start the car, it'll idle at 2000rpm. It never idles lower. I thought that once it warmed up, it was supposed to idle regular. Well, the temp was 200 and I left it running for a few minutes and it didn't idle normal.

The butterfly was fully vertical...I saw that the choke was working properly. Connecting the heater wire helped a lot. I read that you have to tap the gas after it warms up so it will go into regular idle. So I tapped the gas and it continued to idle at 2000, THEN IT DIED.

Started the engine back up without giving it gas....idled at 1500 then died. It can't stay running and I don't know why.

Any suggestions??

 

Actually the sticker under my hood says the fast idle is supposed to be set to 2200 rpm.

Did you set the idle screw on the driver side? If not set it so it keeps the rpms up after its warmed up, so when you tap the gas and the fast idle disengages, you can keep it running while lowering adjusting it.

 

The idle screw on the drivers side is set....I can try pushing it in more, but I don't know that it would help much. Because it doesn't try idling at all...it just wants to die.

 

Set it so it idles high maybe 1500+ rpm. Once the fast idle disengages try lowering it. Right now it could be set too low.

 

There's some adjustment information in this thread that may help (has some pictures):

https://www.thirdgen.org/forums/carb...ms-please.html

If attempting to properly adjust your fast and curb idle don't help, post back, although I'm not exactly sure WHO's doing WHAT in this thread.

 

I put my old carb back on and messed with the idle screw some and got it to idle around 900 or so. Doesn't die in traffic, drive it hard and push in the clutch and it idles normal, doesn't want to die...only thing is, I haven't let it get fully cold then try and start it back up. We'll see what happens in the morning.

The new carb, I have no idea why it's dieing when it's warmed up. Thought it would be a simple fix...slap on the new carb and the choke worked so I was excited....then it ends up being another problem.

Only one thing....there is a black electrical connector on my old carb on the choke side. But on this new carb, it's blue. Does that affect anything, or is it just because it's a different year or what?

 

New carb: was the M/C solenoid clicking and did you plug every vacuum port to verify no leaks? No other changes to your engine, everything still stock? Did someone have a rear vacuum break?

Think we've run Jordeezy off to a new thread.

 

I have my car running fine now. Thanks to all!

 

Good to hear jordeezy!

84z28, since you got two carbs why not rebuild the new one with the instructions naf gave you?

 

well i dont have any of these vehicles but i have a carborated truck it gets a high idle 1500rpm for a while then randumly at a stop light when the clutch is in u hear it drop to 500-600rpm once in a while it will stall i adjusted the idle screw nothin it idles faster but not lower. i put in a new idle speed controll actuator. i dont know its and 1986 truck idk what it could be its annoying at it eats at my gas milage. could it be an egr valve cloged?

 

Is it supposed to click when the car is running, or when the ignition is on or what?

 

Both, the MC solenoid should start clicking when the ignition is first turned to run and continue clicking once the engine is running. The rate of clicking (measured as dwell) adjusts the mixture.

If the ignition is in run and the engine is not started after 30 seconds or so it will time out and stop clicking.

 

I actually heard the clicking once when the car died. I thought it was the distributor or something clicking...it was kind of fast. Could that be it?

 

That's it. Let us know what your carb is specifically doing now.

Your re-built carb may require some adjustments to run most efficiently. Did you put it on and try to get it to idle smoothly at around 600 rpms when warm by adjusting the curb idle screw per the linked instructions?

 

Hi guys, just registered and noticed this post from awhile back. I've got an 83 Z with stock 305 and stock E4ME. I recently have been having issues with an idle problem on my Quad. After warmed up and driving then pushing in clutch to stop, the idle hovers around 1300rpm. It will do this for about 5 secs then drop to where I have curb idle set (800rpm). It is not as drastic going stop sign to stop sign but very noticeable when going say down a country road and then coming to a stop. I'm thinking vac leak maybe?