Does this sound like a carb problem to you?

I am trying to narrow this down.

First, I've got an 84 L69, which I can't get running right. I've got a vac advance distributor, and timing is set at 8*. I have disconnected all emissions as well as the computer. I thought I had an ignition problem so I eventually changed every component. The timing is on, advance, mech and vac work fine.

Right now I have the computer controlled carb on, which should be running rich since it is disconnected.

As the car warms up, the idle becomes weak, won't take a load. The throttle response is more like engine kill. I have had some back fire through the carb. I've driven 3 miles in the past 4 or 5 days and spent hours trying to tune it in the driveway, and used over a 1/2 tank of gas now.

Is there any hope? I have a 4011 series holley that I need to rebuild, but was hoping to get this running first. The car runs so poorly, I can't tune the holley.

What should I try?

 

It sounds like it's time for a new carb. Try checking the throttle shafts and see if they are loose in the carb. Most likely they are, this is causing a big vacuum leak that is interfering with the vacuum signal and really messing up how the carb responds. Of course it could be a lot of other things but it's hard to say listening to it run on a message board, if you know what I mean.

 

Flash,

I do know what you mean. I can tell you that when cold, the car runs much better. At just slightly warm, it starts playing these games.

Also the idle will jump from 750 to 1500 with no rhyme or reason, it's almost as if the advance were suddenly engaged......it's even done that having the vac advance hooked up to the manifold.

Unfortunately, the other carb I have is not yet ready. I'm going to order a holley book and rebuild kit tonight from summit.

I'll let you know.

Oh, yeah, it is supposed to be running rich without the computer correct? Well, it's lean!!!

 

If you have a vacuum leak (a big one usually) then the engine is pulling in air through somewhere other than the carb. That mean it isn't getting metered by the carb so the carb is not putting in the gas to the proper A/F ratio. This will cause a lean condition and cause the RPM fluctuation.
I know everyone says if you disconnect the CC control it should run rich. But when these cars first came out a lot of people disconnected them with no noticeable difference so they could bypass the computer and run hotter cams.

 

I've tuned the carb, and for the most part, the back fire through the carb is gone. Still there a little bit, but the initial advance is only at 6*. I show between 6 and 7 pounds of vacuum. Does this sound about right?

 

vacuum is measured in inches of mercury. 6 or 7 is way too low for vacuum.

 

Give it up. Without the computer control, there's no way to "tune" a CC carb.

If you insist on continuing down this path, put on a non-CC carb.

------------------
82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, TBD heads, Hooker headers & y-pipe, 3" Catco cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

i also have this problem with my 84 HO, every time i hit the gas it sounds like a popcorn machine. the carb is disconnected from the computer and has an open element air cleaner with no exhaust (hollow cat no muffler) i don't think there is anything that can be done but to get a new carb. and i think you need to change the distibutor also.

 

As ODB said, your vacuum is way too low, you have a big vacuum leak, you need to find it and fix it.