cylinders 2 and 5 don't work
Thread Starter
Pro
Joined: May 2004
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From: caraquet N.B Canada
cylinders 2 and 5 don't work
Last fall just before storring my vette i notice that i was running rough so i have check compression and was good but when i remove the sparkplug wire on the 2 and 5 cylinders nothing change as how the engine run so sound like they don't work. I did change my distributor and all wires and sparkplugs. I also remove the valve cover and everything seems ok.
What could be wrong?
What could be wrong?
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
You would have to have the valve covers off, and turn the engine by hand, making sure that all the intake and exhaust valves are opening and closing as they should, with the same extension that the other cylinders all share. If either of the valves on that cylinder are not opening as the others should then it might be a wiped lobe. Also, there could be carbon build up keeping the valves from closing, so maybe look into a leak down test.
A good way to clean that carbon out, is to spray some water from a spritzer bottle into the carb with the engine running. A few evenly spaced sprays will clean out all kinds of junk.
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From: caraquet N.B Canada
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Look for a vacuum leak. Those cylinders are on same intake plenum section (dual plane I'm assuming). They fire consecutively on that plenum bank and a leak can affect both cylinders.
Check carb gaskets, vacuum hoses etc.
JIM
Check carb gaskets, vacuum hoses etc.
JIM
Burning Brakes
Joined: Mar 1999
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From: CA
Thread Starter
Pro
Joined: May 2004
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From: caraquet N.B Canada
I got a new intake and carb (edelbrock)waiting to be installed. Should i install them to see if it doesn't cure my problems?
The only thing i would ruined are my gaskets.
Other than that i might just go for a crate engine from GM.
The only thing i would ruined are my gaskets.
Other than that i might just go for a crate engine from GM.
Last edited by den(thevetteman)78; May 12, 2008 at 11:38 AM.
Thread Starter
Pro
Joined: May 2004
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From: caraquet N.B Canada
Burning Brakes
Joined: Jan 2007
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From: Port Clinton Ohio
St. Jude Donor '08-'09-'10-'11-'12-'13
Does the engine sound ok when it's running? I mean is it knocking or tapping? If not, I think I would go ahead and change the intake and carb and see if it helps. While you have the intake off, you could take a look at the cam and see what it looks like.
Melting Slicks
Joined: Dec 2006
Posts: 2,669
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From: Kingston Ontario
I would be tempted to pull and inspect/read all the spark plugs. If you read the condition of the spark plugs; that will tell you if you have an ignition or fuel problem on 2 and 5 cylinders.
I would have to suspect wiring if you disconnect #2 or #5 and not notice a change in performance/operation. A leakdown test would be a better test as opposed to a compression test. If your problem is in the heads then unfortunately an intake manifold and carb replacement won't be any help to you. I would look further into the problem before changing components.
I would have to suspect wiring if you disconnect #2 or #5 and not notice a change in performance/operation. A leakdown test would be a better test as opposed to a compression test. If your problem is in the heads then unfortunately an intake manifold and carb replacement won't be any help to you. I would look further into the problem before changing components.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Do you get normal flashes on a timing light connected to those cylinders? If so, your plugs are firing OK. Remove valve covers and pull the coil wire so that the engine won't start. Turn it over and watch the rocker arms for movement. All the intake valves should lift the same amount, and all the exhaust valve should lift the same. If you are getting good cam lift and plugs are firing, you must have some valve damage or intake manifold gasket problems. You must check valve lift and plug firing to diagnose this problem.