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Discussion Starter #1
I recently bought an 03 MDX on the cheap, it ran and drove, but had some noise in the engine. Compression test showed low compression in front bank, with #5 worst at 110 psi dry. 4 and 6 around 150. Back bank all 195 to 205.

Checked timing marks and they appear to line up. Can miss adjusted valves account for low psi? PO had a valve adjustment recently completed.

Incidentally wet compression test had 4 and 5 jump by 20 and 30 psi and that was marvel mystery oil not 30w as recommended.

So thoughts on compression numbers and possible valve adjustment?

And I am looking for a service manual for this 2003 MDX. I know helms had an expensive one, Haynes had an eh one. Anyone have or know anything about one from Acura Honda PDF Service Repair Manuals Download - AutoManualSource ?

If there is a pdf one available, please pm me a link, I'm not opposed to sharing of manuals.

Thanks
Bratcop

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I am no expert, but it could be a combination of things. These VVT engines can be tricky. You could have internal damage to the engine. Your cam phasers could be going out. You could have weak valve springs. I would look at a used engine, but I would NEVER by one online. Better to find it local.
 

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Discussion Starter #3
Well I'm not replacing the engine, I'll rebuild it for less than a used one and it will be like new. I'm still interested in a service manual and ideas on the head/compression issue

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Don't know the total mileage on the motor, but if it's a high-mileage motor, AND the PO just recently adjusted the valves, and that adjustment was the first for the motor, it's always possible that the valves were damaged before the adjustment. I hesitate to offer advice about this, as I have no direct experience with bad valves in my MDX (happily), and I'm not entirely certain what KIND of valve damage occurs when you far exceed Honda's 100,000 mile adjustment protocol. Might be worth checking into. Or, there's little doubt that mis-adjusted valves could cause the problem. The good news is that it's really not at all difficult to check and adjust the front bank. The rear's not a whole lot worse - just a lot more of it's done by feel, and the wiring harness is awfully tight.
 

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Discussion Starter #6
Blown head gasket and poorly misadjusted valves on head with bad gasket fyi

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