Carbon Buildup in Carb

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danielb927

danielb927

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Anyone know what would cause this?

p1020469u.jpg


The car idles very rough, drops vacuum below ~1000 rpm, and I can't get it to idle in drive without having the idle in park around 1200 rpm. I'm still trying to get to the bottom of it. Have the valve covers off right now to see if anything is obviously bad there but nothing jumps out at me.

Thanks in advance. Getting this figured out is a headache, I just want to enjoy driving the Duster again!!
 
First thing that comes to mind is a vacuum leak. Do any of the lines feeding off a vacuum source have any slits, cracks, or obvious holes in them? Check the hose going to the pcv, vacuum brake booster (if equipped) and vacuum advance. Check around carb base for any base gasket leaks. If nothing surfaces from any of this, get out a can of WD40 and carefully spray around intake mating surface with the engine running. Listen for changes in engine speed and smoothness. Throw a vacuum gauge on it to see what Hg it pulls.

If not a vacuum leak, I would turn my attention to timing. Make sure that it is steady at idle and set accurately. Plug the vacuum advance while checking.

Lastly, how does it run down the road at speed? Any backfires or hesitation from a stop, or upon moderate acceleration?
 
I guess I should be working harder to find a vacuum leak rather than moving on to the next thing. There's a vacuum splitter in the manifold with about 4 hoses coming out of it plugged by screws, I'll find a manifold plug and then see how it runs. PCV and vac advance hoses are okay (no power brakes), and I tried spraying carb cleaner around but didn't find any leak.

It runs fine at speed but stumbles a little getting off idle.
 
It's a brand new carb with 1500 total miles on it tops, I just installed it last spring, if that helps.

Also I missed one of MOPARJ's comments. The timing is definitely not stable at idle, it wobbles around a couple of degrees. This is when it's at real idle, 700ish rpm in drive, not 1200 in park. It's steady once it gets above the part where the vacuum is low and it wants to quit running.
 
When I ran a shiny race Demon carb once it got carbon below the boosters after 1,500--2,000 miles. Was running just fine, no problems at all.

I'm forgetting which intake I had on it, it might had been the RPM, no oh I think it was an Offy 360, those single plane intakes with a divider.

I was bummed out and cleaned it up with carb-brake cleaner, look so dirty.

My old engine was an oil burner yet ran good, used an MSD 7 to keep the plugs firing..it didn't smoke heavy expect on starts, the rings were worn and same with the valve guilds
 
well..where is your timing set at?

just because it is a new carb...does not mean the initial shot from the squirter is right...
 
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