Popping through the carb problem.
#1401706
03/13/13 12:49 AM
03/13/13 12:49 AM
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Joined: Dec 2003
Posts: 36,840 South San Francisco, Californi...
MidPenMopar
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I just started am having a problem with the roadrunners 383 backfiring through the carburetor almost all the time. The only way not to have it do that is to keep the engine above at least 2500 RPM. So just trying to drive down the street I sound like a popcorn machine. The carburetor is a 650 Edelbrock Thunder series and probably only has a thousand miles on it or so. I am running a Petornix igniter and just installed new Accell plugs and new Accell ceramic tipped wires just in case it was arcing through the wires and misfiring. The thing is it wont backfire unless under a low RPM load (like running the engine in say at 2000 RPMs or so in overdrive) . I checked with my timing light and the timing chain seems not to be slipping. If I keep the RPM's up it wont backfire, like say manually shifting from 1st to 2nd, to 3rd to 4th and it wont backfire no matter what I do unless under a load so I am stumped as what to look for next? Could this be a issue with the transmission not in sync with the Throttle Position Sensor maybe? One note is it used to do this exact same thing when the engine was not up to full operating temperature, but once it hit 180 degrees that popping would go away. Now it acts like this even at full warm up. Any thoughts on why this may be happening all of a sudden?? Stu
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Re: Popping through the carb problem.
[Re: MidPenMopar]
#1401707
03/13/13 01:14 AM
03/13/13 01:14 AM
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Joined: Feb 2003
Posts: 4,826 Castlegar, BC, Canada
That AMC Guy
master
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master
Joined: Feb 2003
Posts: 4,826
Castlegar, BC, Canada
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I'd pull a valve cover just to be sure.
Just recently had this happen to a friends' Chivvy 350..... what had happened was a pushrod broke through the rocker and the exhaust valve on one cylinder was now no longer working!
Bloody Mary, Full of Vodka, Blessed art thou among cocktails....
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Re: Popping through the carb problem.
[Re: That AMC Guy]
#1401708
03/13/13 01:58 AM
03/13/13 01:58 AM
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Joined: Jul 2011
Posts: 972 Chicago
PurpleBeeper
super stock
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super stock
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Posts: 972
Chicago
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If it were a Holley, I'd say "power valve"... but it's not a Holley. A pop out of the carburetor sounds like an intake valve is not sealed all the way and the fuel in that cylinder is igniting back up through the carburetor. A bent intake valve, bent pushrod or funky rocker all could do that, or even a weak valve spring or burnt valve seat. Maybe run a compression test & see if one cylinder is really low compared to the others?
70 Roadrunner convt. street car
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'04 4.6 SOHC, NOS, auto, lowered
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Re: Popping through the carb problem.
[Re: 1_WILD_RT]
#1401713
03/13/13 10:28 AM
03/13/13 10:28 AM
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Joined: Dec 2003
Posts: 36,840 South San Francisco, Californi...
MidPenMopar
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Yep that was my first thought when it started happening as a couple of the old wires had burned through near the headers. So i figured that was the cause and put on those new ones with the ceramic plug ends. Still the same. If it was a miswired situation it would have that problem all the time, not just under a low RPM load like it does now. If i manually shift the automatic transmission through the gears and hold the revvs above say 2500RPMs it runs fine and no backfiring. The issue only comes when i am on the road and the engine is turning low RPMS. You can staticly revv the engine to redine without any issues at all.
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Re: Popping through the carb problem.
[Re: MidPenMopar]
#1401714
03/13/13 10:47 AM
03/13/13 10:47 AM
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Joined: Oct 2011
Posts: 517 ND
dodgedon
mopar
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Posts: 517
ND
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I'm going to say its too lean. The same as when its not up to temp. I have had this problem with Eddy carbs before. More so on trucks... When under load they pop back. You can have the same effect when the choke is off and the engine has not completely warmed up. Lean pop...
67 Charger 383 auto 75 Dodge CNT 800 CAT Diesel 2012 Ram Crew cab 5.7 4x4
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Re: Popping through the carb problem.
[Re: dodgedon]
#1401716
03/13/13 11:25 AM
03/13/13 11:25 AM
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Joined: Dec 2003
Posts: 36,840 South San Francisco, Californi...
MidPenMopar
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Quote:
I'm going to say its too lean. The same as when its not up to temp. I have had this problem with Eddy carbs before. More so on trucks... When under load they pop back. You can have the same effect when the choke is off and the engine has not completely warmed up. Lean pop...
Im thinking that my be the issue as it seems to make the most sense. Since nothing was changed inside the carb though how could this happen??
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Re: Popping through the carb problem.
[Re: stumpy]
#1401720
03/13/13 07:32 PM
03/13/13 07:32 PM
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Joined: Dec 2003
Posts: 36,840 South San Francisco, Californi...
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Quote:
Check the inside of the distributor cap for carbon tracks. I have seen that happen before.
Just checked and the distrubiter cap and it looks good.
Things i did before this problem happended.
I took my TTI headers and sent them out to be recoated and then reinstlaled them as well as putting in those Accell shorty header plugs.
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