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Old 04-03-2020, 12:34 PM   #1
Shadow01
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Compression results in. What's most likely broken?

Ok guys, I did a compression test but no leak down yet. Car sounded and felt like it was running on 5 cylinders. Happened after downshifting and overtaking a Prius lol. I was burning a quart of oil every 60-100 miles and I replaced all culprits (vanos, valve cover, ccv, disa, intake boots and a lot more but it was still burning). My assumption: Engine internals r shot, maybe piston rings??
Compression results dry (didn't do wet,):
1 - 190
2 - 15
3 - 195
4 - 198
5 - 195
6 - 195

Spark plugs were wet for all 5 cylinders and cylinder 2 looked brand new (still shiny probe).

What do u guys think the culprit is? Or what should my next step be? Leak down? Thanks!!
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Old 04-03-2020, 02:24 PM   #2
77'911
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Sorry to hear. You might consider scoping the cylinder so you see what's going on. 15 is quite low, IE usually a blown out ring or completely burn't or bent valve. If it's a ring, you'll see scoring on the cylinder walls. Does the plug look beat up from that cylinder?
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Old 04-03-2020, 11:22 PM   #3
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Harbor Freight has a color LCD borescope you can take a look for around $70 I think. I've had mine for several years and am happy with it and have had a lot of odd uses for it. Perhaps a hole in the piston? I can't reconcile burning lots of oil with the perfect new looking spark plug in the dead cylinder. You've sure got me curious.
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Old 06-02-2020, 12:58 PM   #4
Shadow01
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Bought a brand new 2020 SI Coupe and I've been enjoying the worry free, high mpg, drive it like you stole it feeling. And that turbo..ahhhh smiles
Anyways back to the E46, I've been soaking the toasted cylinder with Seafoam "Deep Creep" and my latest compression test showed 70! Far from the 195 of her sisters but much better than 15 she originally clocked which is tellin me maybe I didn't completely toast her after all. Greedy ho wants some more.
So I'm soaking her some more. I'll keep doing it till the can is empty. I soaked the injectors in Deep Creep and so much black gritty crap came out. This stuff is great!
Give me advice now that compression is comin back! Thank you!!
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Old 06-02-2020, 01:41 PM   #5
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Giving how this apparently happened - a money shift - I think you have a major problem with a piston ring or valve. I don't see many stories of people coming back from near zero compression without taking the head off.

I suppose It IS possible you have a stuck piston ring, but I don't think it's likely you will restore compression with a soak.

Last edited by Effduration; 06-02-2020 at 03:17 PM.
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Old 06-02-2020, 03:00 PM   #6
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Do a leakdown test. You don't even need a proper leakdown gauge or need to know what the % leak down is. Just put some compressed air into that cylinder at tdc to get an idea where the lost compression is going. Use the hose from the compression tester and remove the Schrader valve.
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Old 06-02-2020, 03:08 PM   #7
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Likely a bent valve or two, use a borescope. Hopefully just that and not a snapped valve making the top of the piston & bore look like the surface of the moon.
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Old 06-02-2020, 04:36 PM   #8
Shadow01
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Ok I'll try that. And for the record, I didn't money shift.
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