Pop, Sneeze, Cough... Zoom!

fccperdiem · Posted: Tue Oct 15, 2013 9:40 am Post subject: Pop, Sneeze, Cough... Zoom!

This problem is driving me nuts. It all started a couple weeks ago, when I pulled into the driveway after a nice ride. Everything was running great! I came back out a few hours later to run to the store, and it was damn hard to start. Normally, I give the gas pedal a quick push, let off, clutch in, turn key...running. This time, I had to give it half/ full throttle just for it to start! I played with a few things, got it started, but it has a pop out of the left carb (#4 cyl, I think) at idle. When pulling away from a dead stop, it stutters, pops and coughs through 2500 RPM, or so, then minimizes. The only time the stutter goes away is if I bury the pedal. Then its smooth as silk. When it warms up, the pops transition from the carb burp, to a muffled backfire through the muffler. I know the two symptoms sound like lean conditions, or leaks, but I've played around with jetting and tightened everything I can get a wrench on.

I have replaced/ adjusted the following;
-- Replaced Magnaspark w/ known good 009
-- Replaced plugs
-- Rebuilt carbs with new gaskets/valves
-- Adjusted valves to 'loose zero'

2017cc
Tims Stage 2 heads
110 cam w/ 1.1-1 rockers
A1 1 5/8 header
Magnaspark dizzy
Electric pump regulated to 2 psi

40mm Webbers with 34mm Vents (were 28mm vents, but changed them during the rebuild. Didn't change the problem though)
135 mains
55 idles
200 airs

Any ideas?
_________________
Eric
Beard Fire Metalworks
Ellsworth, ME
207-242-0016
www.beardfiremetalworks.com

VWporscheGT3 · Posted: Tue Oct 15, 2013 9:52 am Post subject:

check your jets... sounds like they're dirty.
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[email protected] · Posted: Tue Oct 15, 2013 10:53 am Post subject: Re: Pop, Sneeze, Cough... Zoom!

fouled plugs from 55 idles. Change them to 50s and re-adjust the idle mixture. Plugs will clean up quickly with proper jetting.
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fccperdiem · Posted: Tue Oct 15, 2013 10:58 am Post subject:

John--Wouldn't fouled plugs cause a problem over time? This problem happened all at once.

VWporscheGT3-- The carbs have been apart and cleaned (ultrasonic and soak)
_________________
Eric
Beard Fire Metalworks
Ellsworth, ME
207-242-0016
www.beardfiremetalworks.com

[email protected] · Posted: Tue Oct 15, 2013 11:05 am Post subject:

normally, yes.

If it happened suddenly I'd look at a plugged idle jet.
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VWporscheGT3 · Posted: Tue Oct 15, 2013 12:34 pm Post subject:

clonebug · Posted: Tue Oct 15, 2013 3:02 pm Post subject:

Carbs could be clean but the idle jet could have a piece if dirt in it.
Pull them all and blow them out good.
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fccperdiem · Posted: Tue Oct 15, 2013 3:25 pm Post subject:

Pulled idle jets. All clear, and debris free. Installed, still sputtering.
_________________
Eric
Beard Fire Metalworks
Ellsworth, ME
207-242-0016
www.beardfiremetalworks.com

sambabus · Posted: Tue Oct 15, 2013 4:53 pm Post subject:

Check the plugs, I had one foul shut on me and the engine ran like that. If you pull the wires one by one it should tell you where it happened.
_________________
1971 Westy, 2017cc 78.4 x 90.5 Tims Stage 1 plus 42x37, CB 44IDF's, 135 mains, 175 airs, F111, 50 idles, Engle 110, 30mm, 009, single QP, DD CHT 300*f, VDO oil always 180* Build: http://www.thesamba.com/vw/forum/viewtopic.php?t=541370
1970 convertible bug, 1835cc, single 40IDF, disks.
Symptoms Solved and Fixed http://www.thesamba.com/vw/forum/viewtopic.php?t=551358

fccperdiem · Posted: Tue Oct 15, 2013 5:03 pm Post subject:

Replaced the plugs
_________________
Eric
Beard Fire Metalworks
Ellsworth, ME
207-242-0016
www.beardfiremetalworks.com

fccperdiem · Posted: Sat Oct 26, 2013 6:18 am Post subject:

#4 carb throat had a partial block in the second progression hole.
_________________
Eric
Beard Fire Metalworks
Ellsworth, ME
207-242-0016
www.beardfiremetalworks.com

d3ac0n · Posted: Wed Oct 30, 2019 9:16 pm Post subject: Re: Pop, Sneeze, Cough... Zoom!

In regards to carbs sneezing\caughing\popping, I had this issue, come to find out my spark plug wires were not in the correct firing order on my distributor. Google search vw bug firing order for clarification. Very simple easy fix! Cool


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