Car is Stalling Under Acceleration?

[slowestmonte]

So I have an 88 Monte Carlo LS with the stock 305, but I recently removed the computer and swapped in a 600 CFM Holley 4160 list #1850 and an Accel red top vacuum advance distributor (I also wired up the torque converter lockup, but that's not relevant to my problem. I have adjusted the air/fuel mixture screws and the accelerator pump along with the distributor and the vacuum advance as best as I can, but the car still bogs and tries to stall if you give it more that slight throttle from a complete stop, but once you hit about 1300 RPM, you can floor it and it runs fine. In park the car is idling at roughly 1400-2000 RPM and in drive it is 800-1200 RPM, but the idle adjustment screw is all the way out. The electric choke is not currently hooked up, since when it is whenever you rev the engine the idle shoots way up to like above 3000 RPM. Does anyone know how I can fix these problems? The carb was brand new rebuilt before I bought it with 66 jets, a 9 plate, a plain secondary spring, and 6.5 power valve.

 

[pontiacgp]

first off you need to hook up the electric choke before you do anything else

 

[slowestmonte]

Like I said, when I do that the car's idle jumps way up to unsafe RPMs and won't kick down.

 

[pontiacgp]

Like I said, when I do that the car's idle jumps way up to unsafe RPMs and won't kick down.

you should buy a book for your carb, without the choke connected the choke will always be on and on fast idle.

 

[slowestmonte]

How could the choke be on high idle when it's not hooked up if the idle jumps up with it hooked up?

 

[airboatgreg]

You can't fix a cold drivability issue until the car runs good hot. Rule choke out on hot engine. Make sure it is off
Idle screws out means to lean. Pinch all vacuum hoses off to see if you have a vacuum leak. Spray some carb cleaner with a red nozzle straw on it around carb base and intake to see if engine performance changes. IE vacuum leak. Disconnect EGR valve and see how it runs and put your hand on it when engine is hot. If it burns your hand EGR may be sticking open or misrouted vacuum to it. Make sure timing is close and disconnect vacuum advance to see if makes a difference. Start here and let me know

 

[slowestmonte]

I no longer have EGR, just have a blockoff plate and capped lines now, but I will try checking for vacuum leaks around the base of the carb tomorrow, since I'm using an adapter plate and I have a suspicion that may be part of the problem. Will let you know.

 

[Clutch]

It sounds like vacuum issues to me

 

[axisg]

First off I know little about edelbrock carbs but I assume they work the same as any other carburetor. As its not a qjet ( factory ) check the linkage to see if anything is binding.
You changed both the distributor and the carb at the same time which throws everything out the window. You could have too much or too little advance timing, let alone vacuum timing. Then you also have a new carb to deal with.

sounds like you have a couple problems. Air leak and tuning. I think Greg got it backwards as the further in the mixture screws are turned in the leaner the mixture and backing them out fattens it up. Sounds to me like possibly at idle you have an air leak which is bumping the idle up by sucking in more fuel. Compounding that likely the carb is set way too rich. So it's either not breathing ( choke flap closed ) or too much fuel with the mixture screws backed out too much. This would want the motor to pull higher RPMs to burn off all the fuel being dumped at it ( which is why it runs better above 1200 rpms ). This would be a situation where at idle you are fouling the plugs with too much fuel and not enough air at low rpms. Leaning it out will help.

Once you have no binding linkage set your base timing. I like 10 deg at 1000 rpms with no vacuum advance as a starting point. Plug all the ports on the carb.

So if you need to then wedge the choke open and get the car warmed up. Sorting out any and all the air leaks. Again you need to plug everything including the vacuum advance and check the base plate for leaks. Once that's done and leak free then add 1 thing back at it at a time. ( really only need vacuum advance and pcv until its sorted further )
Once its all set up and leak free you can work on the curb fuel mixture for max vacuum vs idle quality making sure the setting are the same ( turns in and out ) on both sides.

This will get you 80% of the way there. The car should start warm, idle reasonably well, and drive

Then figure out what is happening with the choke. Choke should have a "cold idle" setting screw which you can adjust to get the idle down when cold. Flap on the carb should close when cold and open gradually as the car warms up.

In the end you should be able to step on the gas when cold to close the choke and set the fast idle. It needs to open gradually as the engine warms then you need to have the ability to idle that motor down to 650 rpms or less and have it stall out. Anything less than that and you have a problem.

What happened to the Qjet BTW ? The general spent a fortune getting this stuff to work and I dont think the aftermarket can do a better job myself.

After you get your baseline sorted out then you start with the tuning to get you closer to your 14.7 A/F ratio at idle and cruise. A good timing gun with advanced readout along with an A\F mixture gauge will be your best friend and save you a ton of hours in both fuel in tuning. The first 80% is easy, its getting that last 20% that is a challenge.

 

[slowestmonte]

You were right airboatgreg, it was the carb spacer. I sprayed some carb cleaner around the base and it bogged bad, so I'll be pulling the carb this weekend and putting RTV on it. Also the original Qjet was shot, and I think the computer and possibly distributor were also having issues due to many other little problems, so I decided I would just go all aftermarket, but if it were just the carb I would've just had it rebuilt.