4.6L (1996-2004 Modular) Mustang Technical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within.

How to check for bad valve?

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Old 08-30-2007, 09:26 AM
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StangEatsRice
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Default How to check for bad valve?

Is there anything i can do to check for a bad valve or somthing in the head besides removing the head itself.. I bolted down the wrong side camshaft in last time i tried the pi cam swap, turned the crank, ptv contact, put it back to tdc, through the old cam in, turned the crank, everything was fine. Would bolting down the wrong side cam in the head do internal damage? I never tried turning the car on only turned the crank about a 1/4 turn if that and felt ptv. Would a compression check for all eight cylinders tell me?
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Old 08-30-2007, 09:33 AM
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4.698GT
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Default RE: How to check for bad valve?

If you didnt turn the engine with the starter, everything should be alrite as long as you weren't trying to force it. A compression check would be the ideal way to check for a bad valve, ring,ect.
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Old 08-30-2007, 09:35 AM
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contentsunderpressur
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Default RE: How to check for bad valve?

+1 those valves are pretty strong. As long as you didn't try forcing it you should be fine.
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Old 08-30-2007, 09:37 AM
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Default RE: How to check for bad valve?

I doubt you damaged anything but you could do a leak-down test on the cylinders in question.A compression test could be useful but unless the valve was bent you might never see any real defects.
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Old 08-30-2007, 09:46 AM
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Default RE: How to check for bad valve?

A leak down test? I'll try the compression test and see if i get anything. The car idles 800-1000, revs fine,is hard to get going but once its going its fine as long as im not accelerating fast. I can take the car up to 4,000 accelerating slow with no problems. I didn't really put a lot of pressure on the crank to turn it when it stopped moving but i did stop and try another push.
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Old 08-30-2007, 11:51 AM
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contentsunderpressur
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Default RE: How to check for bad valve?

What exactly does it do when you floor it?
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Old 08-30-2007, 02:21 PM
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Default RE: How to check for bad valve?

The car shakes bad and i can hear the exhaust like shuddering, like its coughing. Thought it was timing, towels in oil galleys, removed em, car runs better and the pi cams are in which make it lil louder but still have bad idle and accelerating problems. Car seems to rev fine, but with me not being able to feel it as if it was going through the drivetrain, idk. When the car gets to a low idle, 650-700, which it only does when its at running tepmerature it shakes (drained coolant and threw in a 180t-stat). Its got to be either a bad valve from bolting the wrong cam in, turning the crank which if the valves are weak then maybe i could have bent it doing that but i didn't think i tried ot push that hard, or my timing is off. Idk the whole car is weird to me now. I guess i got to wait to do the compression tests to really see whats up.
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Old 08-30-2007, 03:00 PM
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contentsunderpressur
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Default RE: How to check for bad valve?

Sounds like it's doing exactly what my car did when I bent a valve. Start your car and let it idle. Unplug one of the coils and listen. If the miss gets worse then you know that cylinders fireing. Go down the line until you unplug a coil and there is no difference in the way the engine is running. That will tell you which cylinder the problem is comming from. Do a compression test on that cylinder and you will probably find your problem.
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Old 08-30-2007, 03:05 PM
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Default RE: How to check for bad valve?

Alright thanks alot man im running to pep boys now to get a compression tester and should be testing them shortly. Will let ya know what happens.
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