Light puttering under idle - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 02-22-2010, 12:58 AM   #11
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If you suspect that, do a compression test. All cylinders should be close to each other. If a valve is burned, it will show low compression.
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Old 02-22-2010, 01:16 AM   #12
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If you suspect that, do a compression test. All cylinders should be close to each other. If a valve is burned, it will show low compression.
Any idea what the compression of an L27 should be around?
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Old 02-22-2010, 08:22 AM   #13
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No idea, it'* more important that they be within 5% of each other.
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Old 02-22-2010, 02:26 PM   #14
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I not able to view clip but it is possible that EGR is stuck open. That will make it idle rough. your description sounds similar to my experience.
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Old 02-22-2010, 02:43 PM   #15
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I'm 100% sure its a burned valve.

Did the old dollar trick:

http://www.youtube.com/watch?v=LSE74XkcHts

Stick the dollar on the exhaust pipe, and if it sucks it in and blows it out repeatedly, its a burned valve.
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Old 02-22-2010, 03:38 PM   #16
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In that case I say do a compression test, it'* about as easy as changing the spark plugs. This will tell you which valve is bad. You can then pull the head and change the valve. If you need a valve, let me know I have a bunch, as I sure so does Bill.
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Old 02-22-2010, 03:42 PM   #17
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In that case I say do a compression test, it'* about as easy as changing the spark plugs. This will tell you which valve is bad. You can then pull the head and change the valve. If you need a valve, let me know I have a bunch, as I sure so does Bill.
Wouldn't a burned valve also imply the possibility of a worn valve guide? Can you really just replace a valve and expect the engine to be back to normal?

A guy from here in the for sale section, 2000bonny I believe, has offered me a complete engine for $150, which i can drive up and pull everything off of, heads included. I wouldn't mind putting new heads on here which I can port to remove casting defects from and have the peace of mind of knowing that I won't have to deal with another possible burned valve somewhere down the line.

What do you think?

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Old 02-22-2010, 03:44 PM   #18
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You wont know that until you have it off the car and inspect it. Getting a valve job would be a wise choice. But then your pulling both heads. If your going to that point, I suggest pulling them both and getting a valve job. Or, find another set of heads, and swap them.
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Old 02-22-2010, 03:52 PM   #19
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You wont know that until you have it off the car and inspect it. Getting a valve job would be a wise choice. But then your pulling both heads. If your going to that point, I suggest pulling them both and getting a valve job. Or, find another set of heads, and swap them.
I edited my post earlier. 85k mile engine from 94 for $150 including all accessories. So I'll go down there in 3-4 weeks after I get back from my honeymoon and pull everything off the engine down to the shortblock. I figure if a valve burned, it was for a reason, and replacing the valve wouldn't fix the reason why I was burned. Replacing the entire valvetrain on the other hand would fix the problem. $150 for heads, intakes, accessories, ICM, coils, and everything that makes an engine run isn't a bad deal at all.

A valve job would cost me $240 plus parts, where each valve and guide that needs replacing is another $40 added, plus seals and etc.
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Old 02-22-2010, 03:57 PM   #20
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Valves burn when they don't close all the way. They need to seat to give off the heat, if not, they just get hotter until they burn. The valve could have been bent, or dirty causing it to stick. But $150 is a good deal for all the parts.
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