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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: xtreme80 on December 06, 2006, 12:31:00 pm

Title: Lag in the throttle?
Post by: xtreme80 on December 06, 2006, 12:31:00 pm

Hey fellas.  After my carb started leaking and flooding my engine at idle, I decided it was time to rebuild it.

I rebuilt it, and the truck runs great again.  We have all the idle mixtures set correctly, and the truck runs great at idle and while driving.

My problem is, when it's at idle, or a low RPM, and I punch it, it bogs down before it finally accelerates.  If I'm sitting in park, and tap the throttle once, the engine bogs down and is about to die.  If I tap it twice, it will kill the engine.  

Also, when I killed it, and then restarted it, I had a nice puff of black smoke coming out.

My first thought was that the idle mixture was not set correctly, and that it was flooding the engine.  However, after a call to my dad, he said that it was set correctly, and that it sounds like something else was wrong, but he couldnt check it out till this weekend.

Anyone have any advice to what this could be?  I'm still pretty stuck on the thought that the idle mixture is set wrong, and it's flooding the engine, but I could be totally off.

*EDIT* It's a 1980 C10 350/TH350/4bbl Q-jet

Edited by: xtreme80 at: 12/6/06 12:32 pm

Title: Re: Lag in the throttle?
Post by: Lt.Del on December 06, 2006, 03:43:00 pm

Are you sure you installed a new accelerator pump???  
And the rod is hooked up correctly?  It sounds like the accelerator pump that is supposed to force gas thru so there will be no lag in accelerator.  

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4

Title: Re: Lag in the throttle?
Post by: xtreme80 on December 06, 2006, 03:59:00 pm

You know, that's the one thing I triple checked when I installed everything.  Even had my dad check it out for me.  If I can't adjust the idle mixture to fix it, then i guess I'm just gonna have to tear the carb apart again!

Title: Re: Lag in the throttle?
Post by: VileZambonie on December 06, 2006, 05:23:00 pm

With the engine idling depress the accelerator pump all the way down without opening the throttle. It should stall the engine. If it stalls the engine the accelerator pump is working. Very simple test to do.

Title: Re: Lag in the throttle?
Post by: xtreme80 on December 06, 2006, 06:03:00 pm

Thanks Vile!  

I'll give this a try tonight, and post up the results.

Title: Re: Lag in the throttle?
Post by: xtreme80 on December 06, 2006, 08:43:00 pm

Ok, I tried the test.

If I push the plunger down slowly, it will bog down, but won't die at all.  If I push it down fairly quickly, it kills it.

Does that sound like a problem with the accelerater pump?

Title: Re: Lag in the throttle?
Post by: VileZambonie on December 07, 2006, 05:58:00 pm

the accelerator pump is working. You can watch it visually if you @#%$ the engine off and look straight down at the discharge nozzles. hold the choke flap open and pump the accelerator a few times and you'll see it spray. Did you set your float level and float drop correctly? You didn't have this problem until you rebuilt the carb?

Title: Re: Lag in the throttle?
Post by: xtreme80 on December 08, 2006, 12:43:00 am

I had my dad help me to set the float correctly, so I'm almost 100% positive it's set right.  

This only started happening after it was rebuilt, so I think this weekend I'm going to tear it apart again and double check everything.