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post #1 of (permalink) Old 06-20-2005, 11:40 AM Thread Starter
 
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Carb problem?

I picked up an '83 pickup not too long ago that I was told had a bad cat-convertor and wouldn't run for more than a mile or two. I towed it home, put on a new cat, muffler, oxygen pump and a tune-up. The thing runs great now except for a surging when it gets up to speed. It almost seems like it is starving for gas when you reach any cruising speed (35, 55, 60, etc). It has plenty of power all the way through the powerband, as long as you are giving it gas, but as soon as you let up it surges terribly. I've replaced fuel pump and filter, but am not sure what to do next, any ideas? The carb is the electronic 4-bbl, which from what I understand is nothing a backyarder wants to take apart? New carb will run about $400 and rebuild is around $350 at a reputable shop. The area that I live in prohibits the removal of all the emission stuff, so am I stuck with getting a new carb? Thanks for any help you guys can provide!!!
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post #2 of (permalink) Old 06-20-2005, 11:04 PM
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Re: Carb problem?

I have a couple ideas. [img]/ubbthreads/images/graemlins/smile.gif[/img] I really wonder if the carburetor is a feedback mixture solenoid carburetor with computer controls, or if the carburetor has an enrichment solenoid! [img]/ubbthreads/images/graemlins/confused.gif[/img] One way to figure things out, does the distributor have a vacuum advance? No vacuum advance on the distributor means your carburetor has a feedback mixture solenoid. Is there an oxygen sensor in the passenger exhaust manifold? This also indicates your carburetor has a feedback mixture solenoid. If you do not have an oxygen sensor, and your distributor has a vacuum advance, then you have the ESC (Electronic Spark Control) system. Check to see if you have a knock sensor by the starter, this also indicates the ESC system. Most of trouble I've seen with the early 80's GM pickups, is knowing what systems are on the engines. I've seen the wrong parts get replaced because of not knowing the difference between ESC and Feedback. Let me know what system you have, I can be of better help.
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post #3 of (permalink) Old 06-21-2005, 12:40 AM
 
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Re: Carb problem?

1st thing i would is check the float lvl, can be checked w/ special tool from otc (not expensive) it fits in the fresh Air tube over the toe of the float. very easy very fast. If your float has sunk or is set low it could cuase the prop you discribed.
Good luck
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post #4 of (permalink) Old 06-21-2005, 10:54 AM Thread Starter
 
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Re: Carb problem?

Dave, well lets see here, the dist. has no vacum advance, it is controlled by a module on the passenger side fenderwell. The oxygen sensor is on the drivers side and is the only one, there is nothing on the passengerside. I assume this means it is a Feedback system? There does not appear to ba a knock sensor either.

JWharden, any idea what would the tool be called? Most of the parts counter guys in my area are lucky to be able to recite their own name, so I am not real confident they will know what I'm talking about
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post #5 of (permalink) Old 06-21-2005, 10:50 PM
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Re: Carb problem?

My first thought would be get rid of the Computer Feedback Carburetor and Computer Controlled Distributor. [img]/ubbthreads/images/graemlins/smile.gif[/img] That's not an option. [img]/ubbthreads/images/graemlins/frown.gif[/img] So I think if it were my truck, I would first unplug the mixture control solenoid, and see if the engine still surges? If the engine runs OK with the mixture control solenoid unplugged, then maybe replacing the mixture control solenoid would be what I'd try next? I might just leave the mixture control solenoid unplugged and hope to win the lottery so I can buy a new truck. [img]/ubbthreads/images/graemlins/cool.gif[/img] If the engine surges with the mixture control solenoid unplugged, then maybe the distributor ignition module is faulty. [img]/ubbthreads/images/graemlins/confused.gif[/img]

Now having said that, let me know what happens if you decide to unplug the mixture control solenoid. If you decide to get rid of the Computer Feedback Carburetor and Computer Controlled Distributor, let me know. I'm sure I have carburetor and distributor sitting on a shelf in my garage, for less money than a rebuilt carburetor would cost. I'm thinking a carb and distributor from a 1980 - 1982 GM pickup with the 49 state federal emission package will have all the correct vacuum hose fittings like your current carburetor, most 1980 - 1982 GM pickups did not have ESC, but some did. [img]/ubbthreads/images/graemlins/confused.gif[/img] The ESC distributor has a 5 pin ignition module in the HEI distributor. The Computer Controlled Distributor has a 7 pin ignition control module. The HEI distributor with the 4 pin ignition module is what I'd use to replace your current distributor.
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