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2010 Acadia 3.6 relative compression

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13 Jan 2020 19:22 #36580 by Cheryl
2010 Acadia 3.6 relative compression was created by Cheryl
I have my scope set on ac coupling across the battery terminals. I’m trying to convince a shop this thing has major mechanical issues. There not buying it saying they can’t see it having issues. Let me know what you guys think. I didn’t have time to sync a coil or anything just got 1 channel going Here is a pic of the results.
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13 Jan 2020 19:23 #36581 by Cheryl
Replied by Cheryl on topic 2010 Acadia 3.6 relative compression
Oh it doesn’t run hardly

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13 Jan 2020 19:59 #36584 by Tyler
Replied by Tyler on topic 2010 Acadia 3.6 relative compression
Did you also invert the voltage trace, in addition to AC coupling? Because if you turn it upside down, you get three strong cylinders and three weak. :silly:

Even if it's inverted, it's still not a good waveform. Timing codes? Glitter in the oil?

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13 Jan 2020 20:34 #36587 by Cheryl
Replied by Cheryl on topic 2010 Acadia 3.6 relative compression
I inverted it but didn’t get a pic with my phone. Shop keeps sayin it’s not mechanical. No timing codes

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13 Jan 2020 20:36 #36589 by Cheryl
Replied by Cheryl on topic 2010 Acadia 3.6 relative compression
That’s cranking only. I couldn’t find a good cam shaft sensor to crank waveform when I seen those humps missing I was like not good for the guy who owns it sucks to be him. Have you personally done many 3.6 liter timing chain jobs??

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13 Jan 2020 21:29 #36591 by Chad
Replied by Chad on topic 2010 Acadia 3.6 relative compression
I'm having a hard time wrapping my head around that one. :blink: A sync would be helpful. :) How does it sound while cranking? Does it have the tell-tale rhythmic cadence?

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

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13 Jan 2020 21:34 #36592 by Cheryl
Replied by Cheryl on topic 2010 Acadia 3.6 relative compression
Certainly does chad. I didn’t get a chance to take another pic. I didn’t invert it in this pic. Just do what Tyler said. If ya look at it upside down it’s missing 3 cylinder compression. If I hook it up tomorrow I’ll get a sync and inverted pic

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13 Jan 2020 21:37 #36593 by Cheryl
Replied by Cheryl on topic 2010 Acadia 3.6 relative compression
I wanted to use my amp clamp but I left it at the house 20 minutes away so I had to do it the ac coupled way hooked up directly across the battery terminals

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13 Jan 2020 21:52 #36594 by Chad
Replied by Chad on topic 2010 Acadia 3.6 relative compression
Ah, I see it, now. B) I misunderstood. I thought this picture WAS inverted. Makes more sense, now. ;) Low compression on one whole bank.

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

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13 Jan 2020 21:56 #36595 by Cheryl
Replied by Cheryl on topic 2010 Acadia 3.6 relative compression
Sorry should of uploaded the good pic. Shop just pissed me off saying it needs an ignition switch nothing mechanical wrong. I said okay let me know how that goes. So chad you do the chains o these engines yet??

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13 Jan 2020 22:03 #36596 by Chad
Replied by Chad on topic 2010 Acadia 3.6 relative compression
Yes, I have done a few of them. They are not that bad, once you gain access to them.

I flipped your pic:


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"Understanding a question is half an answer."
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14 Jan 2020 06:34 - 14 Jan 2020 07:01 #36598 by Noah
Replied by Noah on topic 2010 Acadia 3.6 relative compression
Classic ignition switch :P

"The circuits in cars are not nanby-pamby Chinese consumer electronics "
Last edit: 14 Jan 2020 07:01 by Noah.

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14 Jan 2020 09:40 - 15 Jan 2020 03:31 #36600 by Andy.MacFadyen
Replied by Andy.MacFadyen on topic 2010 Acadia 3.6 relative compression
None so blind.....

To every one here it shouts cam timing on one bank Only way I can think of to prove it is to demonstrate it is only running on one bank by pull injector or plug wires off on one bank then the other

" Designed by clowns surpervised by monkeys. "


Last edit: 15 Jan 2020 03:31 by Andy.MacFadyen.

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14 Jan 2020 16:55 #36609 by Noah
Replied by Noah on topic 2010 Acadia 3.6 relative compression
Just for the sake of discussion, how about a blocked converter on one bank?

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14 Jan 2020 17:03 #36610 by Cheryl
Replied by Cheryl on topic 2010 Acadia 3.6 relative compression
Hmm good thought on the converter. But wouldn’t a clogged converter create higher compression as the engine can’t exhale?? Also I scoped the 4 cam sensors according to Iatn s guy has a known good correlation and mine was way off on one bank
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14 Jan 2020 17:08 #36611 by Cheryl
Replied by Cheryl on topic 2010 Acadia 3.6 relative compression
2 of my cam sensors match as they are over laid in the scope shot. But the 2 are no where close. Sorry it’s not labeled the guys from iatn weren’t either. But if they don’t mTch it’s off...
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14 Jan 2020 17:18 #36612 by Cheryl
Replied by Cheryl on topic 2010 Acadia 3.6 relative compression
For some reason it wouldn’t let me post my scope capture the same way to make looking at both easier for comparison

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