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05-03-2020, 03:27 PM | #1 |
Registered User
Join Date: Jan 2018
Location: TN
Posts: 263
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350 engine idle shake HELP!
I’ve had the truck sitting for about 3 weeks while I redid the door rubber and now when I start it, the engine shakes vigorously. It ran perfect before I let it sit. I’ve checked and rechecked the wires and they are all going to the same spot. I’ve moved the distributor clockwise and counterclockwise to see if the timing was off but it stays rough no mater how far I turn it each way. I put my hand over the top of the carb and it seemed to slow the shaking. I think it may be a vacc leak. How would I check for a vacuum leak? It did this once before and I took off the rotor cap and filed all the buildup off of the points about a 2 months ago. That helped but I don’t see how so much buildup could occur that quick if that is the problem again. .
350 abc crate engine. 3 years old. Edelbrock performer intake, HEI, and stock q-jet. |
05-03-2020, 03:38 PM | #2 |
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Join Date: Jan 2001
Location: Orem, Utah
Posts: 7,941
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Re: 350 engine idle shake HELP!
Carbon arcing in the distributor cap or arcing wires are the two things that come to mind first. Have you tried running it at night to see if there are sparks jumping anywhere?
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05-03-2020, 03:39 PM | #3 |
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Join Date: Oct 2005
Location: Overland Park, Ks.
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Re: 350 engine idle shake HELP!
There is a vacuum connection in the intake manifold behind the carb. If one of the hoses that connect to this outlet fitting comes off the fitting or the other end, it will cause a shake in the engine as this connector goes into a runner that feeds 2 cylinders. It usually connects to the vacuum reservoir ball & the auto trans modulator.
George |
05-03-2020, 04:00 PM | #4 |
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Join Date: Apr 2011
Location: Fairview Park, Ohio
Posts: 1,031
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Re: 350 engine idle shake HELP!
Check all your vacuum lines.
Get some carb cleaner with nozzle. Spray around base of carb and vac line fittings and lines. If the engine Boggs down that means the vacuum leak sucked the carb cleaner in the leak point.
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05-03-2020, 04:24 PM | #5 |
At the body shop.
Join Date: Aug 2009
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Re: 350 engine idle shake HELP!
Dirt in the idle circuit will make them shake too.
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05-03-2020, 04:46 PM | #6 |
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Location: TN
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Re: 350 engine idle shake HELP!
Thanks guys. It started raining so I will try these tomorrow
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05-03-2020, 04:48 PM | #7 |
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Join Date: Jan 2018
Location: TN
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Re: 350 engine idle shake HELP!
Here’s what all the plugs looked like. Maybe time for new plugs?
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05-03-2020, 05:09 PM | #8 |
Just here to tinker
Join Date: Jun 2008
Location: Holland, MI
Posts: 3,697
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Re: 350 engine idle shake HELP!
Throw a set of plugs in it and check for vacuum leaks as mentioned above. The dead give away that it is a vacuum leak is the fact you put your hand over the carb (choked it) and it started running better.
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05-03-2020, 05:42 PM | #9 |
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Location: TN
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Re: 350 engine idle shake HELP!
I ordered a set of R44TS spark plugs along with a new carb stud kit and gasket. The passenger side carb stub was loose. I attempted to tighten it but it happened to be stripped. So that might be where the vacuum leak is.
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05-03-2020, 07:00 PM | #10 |
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Re: 350 engine idle shake HELP!
Well yeah. Always perform a general tune up first it’s its due.
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05-03-2020, 07:29 PM | #11 |
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Join Date: May 2013
Location: Post Falls, ID
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Re: 350 engine idle shake HELP!
My truck idles weird sometimes , when I get "iffy" gas. I recommend topping off with some good premium (Non ethanol if available) and see if it clears up.
Could be a lot of things, but fresh gas will eliminate one variable. BTW Timing NEVER changes while a vehicle sets not running, no matter how long it sets. If it "It ran perfect before I let it sit", the problem isn't the timing. The only way the timing changes if something is moved. |
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