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02-20-2008, 12:12 AM
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#1 |
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Registered User
Join Date: Jan 2007
Location: Beaufort, SC
Posts: 244
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Stumble
I just recently timed my truck, and it seems to be running good thru most of the RPM range except at idle it has a stumble?
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02-20-2008, 12:47 AM
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#2 |
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Registered User
Join Date: Apr 2007
Location: Norman, OK
Posts: 222
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Re: Stumble
Pyro,
Check to see if your carb's accelerator pump is shooting a stream of fuel. HomerJ
__________________
67 C-10 LWB "Cow-butt-spotted" (neighbor's term) - work in progress. 350/TH400/3.73 67 Chevelle SS Clone  454/TH400/3.73
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02-20-2008, 06:41 AM
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#3 |
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Registered User
Join Date: Jan 2007
Location: Beaufort, SC
Posts: 244
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Re: Stumble
and now it back fired thru the carb?
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02-20-2008, 08:21 AM
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#4 |
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Registered User
Join Date: Oct 2007
Location: Garageless, Missouri
Posts: 408
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Re: Stumble
Don't check it's while running. Was it stumbling before checking or changing timing? I have a junk 2 barrel carb on mine until the weather breaks and it does the same. Runs great until I try to get it off idle. Backfire is either off time or possibly not good enough accelerator pump shot of gas. Other things can cause this but you gotta eliminate the normal places.
__________________
R.I.P ESLL Even as the body dies the spirit lives on in the people you touched |
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02-20-2008, 08:22 AM
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#5 |
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Active Member
 
Join Date: Jul 2007
Location: Centrally located between Houston, Austin and Waco. BCS area.
Posts: 7,947
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Re: Stumble
Backfiring thought the carb may be caused by fuel/exhaust leaking out the intake valve. May be a sticking valve, worn out valve or valve seat or even bad cam.
Could still be a timing issue but if it runs smooth most of the time it may be a bad valve. These are usually more noticeable during idle. As the speed increases the missing is reduced somewhat. Do a compression test on all the cylinders to see if there's one that's off by a bunch compared to the others. If all checks out, then you may have a vacuum leak and/or excessive fuel going into the intake area... |
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02-20-2008, 09:36 AM
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#6 |
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Account Suspended
Join Date: Sep 2005
Location: Monroe, WA
Posts: 3,815
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Re: Stumble
Timing first, always.
The question is - what's changed if this is a new problem? |
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02-20-2008, 10:04 AM
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#7 |
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Registered User
Join Date: Jan 2008
Location: SURREY BC, CANADA
Posts: 278
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Re: Stumble
dont forget to try a leakdown test on the cylinders
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02-20-2008, 05:01 PM
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#8 |
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Registered User
Join Date: Jan 2007
Location: Beaufort, SC
Posts: 244
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Re: Stumble
It was running worse before I fixed the timing, It was backfiring even up around 2500 to 3000 rpms before adjusting the timing..
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02-20-2008, 07:50 PM
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#9 |
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blood type; Retumbo
Join Date: Jan 2004
Location: next to my reloading bench
Posts: 10,269
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Re: Stumble
what's it show on a vacuum gauge? you ARE using one right?
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