Car Has No Compression On #4, ...can I take the valve cover off without draining oil? |
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Car Has No Compression On #4, ...can I take the valve cover off without draining oil? |
7TPorsh |
Jun 30 2016, 12:30 PM
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#1
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7T Porsh Group: Members Posts: 2,691 Joined: 27-March 06 From: Glendale Ca Member No.: 5,782 Region Association: Southern California |
A problem has recenly developed and I can't figure it out. The car starts up easy and on the first crank. I let it warm up a few minutes and drive....It drives fine as it's warming up.
Then after about 15 or 20 minutes the engine starts developing a shudder. Idles fine but and can run ok under low load but under some load the #4 cylinder starts popping and firing up through the carb. feels like it's running 3 cylinders and wasting gas. It's been suggested I do a compression test but I'm thinking if the engine runs great cold and while warmin up; the compression should be ok. Is there a case where comprression is ok when cold but low when hot? Can't figure out why car runs great when starts f'n up. 1.7 with dual weber 40 IDFs |
TheCabinetmaker |
Jul 1 2016, 06:43 AM
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#2
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I drive my car everyday Group: Members Posts: 8,304 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
Squirt some oil in the plug hole then retest compression. If it remains at zero look to valves.
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7TPorsh |
Jul 1 2016, 08:24 AM
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#3
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7T Porsh Group: Members Posts: 2,691 Joined: 27-March 06 From: Glendale Ca Member No.: 5,782 Region Association: Southern California |
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Mark Henry |
Jul 1 2016, 09:26 AM
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#4
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
Squirt some oil in the plug hole then retest compression. If it remains at zero look to valves. I'll try this today. How could this help? Stuck valve? Not perfect but an old trick, if it's rings the oil will seal enough to give you a bit of compression during the test. if numbers go up it's rings, if it doesn't likely valves. That said 0 compression I'd suspect a tight valve or dropping valve seat. With a 1.7 I really expect a dropping valve seat....sorry. Head gasket I'd expect a couple of pounds and a hiss/whistle noise. |
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