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  #16  
Old 05-19-2011, 03:29 PM
mickblock mickblock is offline
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Default Re: Mechanic stumped!

Did the mechanic hook up a vacuum gauge?
A bad valve would be more easily diagnosed using a vacuum test since the engine could be run at the effected rpm range. A valve that isn't opening all the way would create a specific pattern in the movement of the needle. Can't catch bad cam lobe/valve action at cranking speed. Unless its real bad that is.
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  #17  
Old 05-19-2011, 03:40 PM
patc890 patc890 is offline
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Default Re: Mechanic stumped!

Both points about the valves are good. The compression was checked twice by two different mechanics and both said it was fine. I don't know enough to know if what you(Botta Ranger) say is right, but it could be.
Also don't know if they used a Vacuum gauge but will ask all these questions.

Thanks.
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  #18  
Old 05-19-2011, 04:54 PM
wvcat wvcat is offline
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Default Re: Mechanic stumped!

When they do a compression test they remove the plugs and crank the engine over with the starter and then compare the readings from all the cylinders. This is a good way to single out a bad cylinder and will tell you that your rings are good and the valves are seating properly. However most engines have double valve springs. One spring can be broken and you can get a good compression reading but under higher rpm the valves can "float" (not close all the way). The motor may run good at low rpm's but miss on higher rpm's or under load.
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  #19  
Old 05-20-2011, 04:47 AM
Botta Ranger Botta Ranger is offline
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Default Re: Mechanic stumped!

Quote:
Originally Posted by wvcat View Post
When they do a compression test they remove the plugs and crank the engine over with the starter and then compare the readings from all the cylinders. This is a good way to single out a bad cylinder and will tell you that your rings are good and the valves are seating properly. However most engines have double valve springs. One spring can be broken and you can get a good compression reading but under higher rpm the valves can "float" (not close all the way). The motor may run good at low rpm's but miss on higher rpm's or under load.
Makes sense. Thanx.
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  #20  
Old 05-20-2011, 06:31 AM
hwhmobile hwhmobile is offline
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Default Re: Mechanic stumped!

for sticky valve and springs try running some injector cleaner or sea foam through it.

Also it could be your timing is off by just a hair.
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  #21  
Old 05-20-2011, 07:22 AM
patc890 patc890 is offline
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Default Re: Mechanic stumped!

Hi,

I have running a lot of injector cleaner through it before the injector was replaces.

If the timing was off would that only effect one cylinder?

I also saw on another thread that a lot of people are having the same problem and some have had to replace the heads. There is a TSP on it also
http://ww2.justanswer.com/uploads/jm...sb05-26-03.pdf

I hope it's not this.
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