1997 compression issues - 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 07-23-2006, 01:06 PM   #1
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Default 1997 compression issues

one of the cylinders is running low compression and as a result I failed the idle portion of the e-test...

this was a scrap car that I've been bringing back to life....so far the cost is just under $2000 including the car and I've done the following:

replaced windshield
new muffler
bodywork
MASSIVE interior clean
rear brakes
brake lines
oil pan
valve cover gaskets (were leaking)


as for the compression....I've replaced the spark plug...next step is wires...from there where should I go?

I was thinking....injector, then head gasket....after that?????
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Old 07-23-2006, 01:12 PM   #2
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Compression on one cylinder? You're heading in the wrong direction.

Rings or valves, typically. Almost never a head gasket. Spark plug is possible, but certainly not a wire.

How about you do a wet and dry compression check to see if it'* the rings?
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Old 07-23-2006, 02:04 PM   #3
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Sounds like he didn't mean compression, maybe he'* getting a misfire code. I can't even figure how a spark plug could be a possibility. Plug would have to be removed to do a compression test. Is there some other way to determine low compression?
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Old 07-24-2006, 05:04 PM   #4
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Ok, here is the story, sorry for the lack of clarity...I was there this morning and got everything cleared up.

At first it was running poorly, we thought maybe a misfire so we checked the spark, replaced the plug, and replaced the wire. Next assumption was fuel, replaced injector...it'* fine, still lousy running. Next was the compression, it was low and ranged from 85-100. Now...I took it to the e-test (just to see if I could luck out) facility and it failed. Here are the readings:

ASM2525 TEST

RPM: 1628
Dilution: 14.8
HC ppm: Limit - 55 , Reading - 19 (Pass)
CO%: Limit - 0.31 , Reading - 0.07 (Pass)
NO ppm: Limit - 408, Reading - 23 (Pass)

CURB IDLE TEST

RPM: 837
Dilution: 9.8
HC ppm: Limit - 200, Reading - 1455 (Fail)
CO%: Limit - 1.00 , Reading - 1.88 (Fail)
NO ppm: N/A


Soooo.....I'm thinking a few things....

1) The valve guides are off a bit
2) Bad rings
3) both of the above

Any other ideas?

The sad part is that it'* #4 so it'* going to be a bit of a p.i.t.a to tear everything apart. I'm thinking I'll try and pull the heads off and see what'* going on in the next few weeks. I just need to get some $$ together to start buting all of the gaskets I'll have to replace on the way. Might as well do the head gasket while I'm in there [/u]
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Old 07-24-2006, 09:29 PM   #5
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burnt exhaust valve
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Old 07-24-2006, 10:03 PM   #6
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What were the other compression readings?
I'd check the resistance of all the coils to rule out an ignition problem for the poor E-test.
http://www.bonnevilleclub.com/forum/...e=article&k=33
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Old 07-24-2006, 10:06 PM   #7
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Idle is a little high, Tried warming the car up first?
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Old 07-25-2006, 03:14 PM   #8
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100 psi on the compression test is fine, as long as the others are the same. 10% variance between cyls is acceptable. So if you had 100, 110, 105, 95, 100, etc, etc, you are probably fine. If all the others are hitting at 100, and this one cyl is 85, it'* probably not the end of the world. Do a wet test and this will rule out rings, and isolate it to the head, etc. Valve guides will most likely not cause this. They will cause slight oil usage, but not likely low compression. Do all the test first, before pulling it all apart. You're going to be pissed if you tear it all down, and spend all the $$$ on gaskets, just to find that you had a bad coil, etc. You'll also be pissed if you tear it down, have the heads done, to find that the rings were bad.
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Old 07-25-2006, 03:45 PM   #9
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Quote:
Originally Posted by Damemorder
Idle is a little high, Tried warming the car up first?
idel high? mine idles at around 900-1000 when warm... 800ish when in Drive... is Mine high also????
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Old 07-25-2006, 04:13 PM   #10
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700 is dead nuts warm idle.
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