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Old 02-11-2014, 07:12 AM   #61
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Then I pull the cover off and take a wrench to the Intake cam: it TURNS counter clockwise (when facing car from front) AND THEN LOCKS. Can't turn it back clockwise.

I thought it was supposed to be always locked when engine is off?
I have the same experience, the actuator does not go back to zero and lock when you shut down. And when I turn it back I get a nice squirt of oil into the air (not into the face yet).

But since mine is running (and have the same zeroing of the cams and the cam sensor ring as you) don't sweat about it.
My take on it is oil pressure advance the cam and the forces/friction in the valvetrain push it back. When you shut down the engine both forces stops simultaneously and there is nothing pushing the cam back to zero.

Have you tried to lock the cam, disconnect the VVT and try to see if stays zeroed (if not oil is getting through)? This would be no different than your earlier attempts with the VVT disconnected I guess.
Remove the Cam sensor and take a picture of the wing zeroed so you have a faster way of verifying (just a thought).

Last edited by NiklasFalk; 02-11-2014 at 07:56 AM.
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Old 02-11-2014, 08:16 AM   #62
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Sounds like there's still some more debris causing problems, or the VVT gear actuator is now damaged or reassembled incorrectly somehow, or it's physically not timed right (Which is unlikely, because it would need to be pretty far off.)

I agree with Reverant.

If you have a spare known good OCV, it can't hurt to get it ready. Maybe debris is in there too. That debris is concerning.
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Old 02-11-2014, 10:04 AM   #63
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Yeah, that's on the list to do today: yank a known good vvt mechanism/actuator/control valve and try those.

Again thanks for the inputs everyone. Hopefully I can get this sorted soon. The car is just begging to be driven
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Old 02-11-2014, 11:11 AM   #64
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its hard to see in the pictures, are all the wipers/leaf springs from the actuator intact?

I also don't see the little rubber shim that goes on top of the spring loaded piston. You say it locks now, so I assume you still have it.


There is a mesh screen at the end of the oil tube that leads to the VVT, it should stop chucks of that size from entering the mechanism. Picture here.
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Old 02-11-2014, 11:14 AM   #65
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I feel like there was a plastic part in the VVT/gear assembly when I disassembled mine. It was about 9mm across and had a hole in the center that was maybe 2mm. I didn't see this in your vvt/gear assembly...

Also, there are "wipers" on the ends of the "lobes" sitting in the slots. Under them are little leaf springs. Were they all there?
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Old 02-11-2014, 11:17 AM   #66
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its hard to see in the pictures, are all the wipers/leaf springs from the actuator intact?

I also don't see the little rubber shim that goes on top of the spring loaded piston. You say it locks now, so I assume you still have it.


There is a mesh screen at the end of the oil tube that leads to the VVT, it should stop chucks of that size from entering the mechanism. Picture here.
Yep, I inspected and cleaned each and every one of them. all are intact and all are installed.
rubber shim? hmmmmmm
the spring is there, and the little piston is there, but I don't recall any shims? maybe that's what those bits and pieces are of? any chance you can find a picture of it?
I'll hunt around the interwebz too and see if I can find what you're describing
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I feel like there was a plastic part in the VVT/gear assembly when I disassembled mine. It was about 9mm across and had a hole in the center that was maybe 2mm. I didn't see this in your vvt/gear assembly...

Also, there are "wipers" on the ends of the "lobes" sitting in the slots. Under them are little leaf springs. Were they all there?
is this the "shim" dave is talking about?

the wipers and springs are all there and all good.
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Old 02-11-2014, 11:24 AM   #67
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Do we even know what you call this thing? I don't even know if this is called the VVT actuator or?

The thing up top is the VVT solenoid assembly I think right? This must be the actuator correct?
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Old 02-11-2014, 11:25 AM   #68
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HERE!
VVT Solenoid assembly. - MX-5 Miata Forum

You are DEFINATELY missing that little plastic thing.

I'd cross post but it's not my picture. (is that against the rules?)
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Old 02-11-2014, 11:29 AM   #69
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THANK YOU

I did not see any shim like that in my cam gear/mechanism.

I guess maybe those pieces I found inside are of it all crumbled up/destroyed?

Now we're getting somewhere (hopefully)
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Old 02-11-2014, 11:32 AM   #70
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the question now is how to get another without paying for a whole damn actuator.

When I took mine apart I lost one of the leaf springs so I had to fabricate a new one from spring steel. It would suck if you can't find a replacement.
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Old 02-11-2014, 11:36 AM   #71
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well if I know what its made of I am pretty sure I can make one. it looks like a round piece of metal or ceramic or plastic or something. like a puck. not too hard to make (or so it seems)
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Old 02-11-2014, 11:36 AM   #72
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BP6D-12-4X0D is the mazda part number you need.
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Old 02-11-2014, 11:40 AM   #73
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well if I know what its made of I am pretty sure I can make one. it looks like a round piece of metal or ceramic or plastic or something. like a puck. not too hard to make (or so it seems)
Without a known good one it makes it slightly more difficult. What seems most important to me is the overal diameter, the thickness, and the hole. I don't know if the other details are important or not.
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Old 02-11-2014, 11:40 AM   #74
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lol I'm not buying a new actuator from mazda. thanks though.

but yeah I guess my only option now is to yank one from spare long block and try it out.
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Old 02-11-2014, 11:44 AM   #75
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I never noticed that on mine. Ok. So let's think about theory of operation...

When no oil pressure is supplied to VVT assembly on cam gear, it stays locked. When oil pressure is applied it advances? Is that correct?

If so, perhaps something causing VVT to advance at idle. (Or basically in all conditions)

What things could cause this?
My understanding of VVT:

with no oil pressure, the spring loaded mechanism in the picture will lock the cam whenever it reaches the fully retarded position.

after starting, oil pressure builds and depresses the spring/piston, this frees the cam to move in relation with gear.

there are 3 chambers as seen in the picture. Each of these chambers has a divider that splits it into 2 sub-chambers. each subchamber has a small leak in it that is used bleed pressure in a controlled manner and lubricate the front cam bearing.

The VVT gear moves away from whichever subchamber has greater volume (pressure)

While the solenoid is an on/off switch, the valve it actuates is not on/off. When you energize the solenoid, the oil moves into one subchamber. When it is denergized it moves to the other. My guess when the solenoid is at rest, this makes the cam retard. reasoning is this: when you turn the ignition off, the ECU kills power to the solenoid, the engine is still spinning, and still has oil pressure temporarily. The gear begins to retard and is in lockup position by the time the oil pressure drops to 0.

so after engine start, the solenoid is supplied a PWM signal. 50% duty cycle on the pwm will cause the gear to hold is position. If the ECU wants the gear to advance, it will increase duty cycle until it finds the postion it wants, then return to 50%. When you disconnect the solenoid from the VVT, you are essentially giving the valve 0% duty cycle and the gear will stay retarded (that is if my above assumption is correct).

If you disconnect the electrical connector and the gear immediately advances, then either my assumption was incorrect, or there is some mechanical fault that is preventing oil from reaching the retard subchamber.

Is it possible to make megasquirt go 100% duty cycle on the VVT? this would be the opposite of unplugging the connector and the VVT should react the opposite way than if you unplugged the connector. Would be a good experiment to see which way the gear goes with increased duty cycle.
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Old 02-11-2014, 11:46 AM   #76
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From my recollection it seemed like a hard polymer of some sort. It wasn't rubbery.
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Old 02-11-2014, 11:49 AM   #77
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That all sounds great and I tend to agree with all of it.

I've tried unplugging the solenoid and starting the car, and it does the same stupid thing.

And since car doesn't want to start, and when it did start before it was drawing next to no vacuum, the only logical explanation I can come up with is that the cam is advanced or advancing all the way. If it was retarded or stayed retarded, it would start and run great, just not make much power.
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Old 02-11-2014, 11:52 AM   #78
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So, perhaps that little puck was installed incorrectly and destroyed itself, explaining why it managed to run correctly the first few short start up sessions. The little puck was destroying itself and therefore the actuator slowly lost the ability to hold itself in the correct position?

I guess I'm trying to see what exactly that little puck was doing (helping guide oil pressure across those three chambers?), and if it could have been installed backwards, causing it to fail?
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Old 02-11-2014, 11:54 AM   #79
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lol I'm not buying a new actuator from mazda. thanks though.

but yeah I guess my only option now is to yank one from spare long block and try it out.
It is a round piece of rubber(could have been plastic, it was hard in either case), it fits into the oval recess, but it does not oval shaped itself. It is not quite puck shaped, there are concave recesses in each side. Not sure If that is important or not. I seem to remember reading about it and someone claimed there was supposed to go in a certain direction. Not sure how true that is though, I just YOLO'd it when I put it together, and it seems fine.

I don't think those metallic looking chunks had anything to do with the "puck" though. I would be concerned how those ended up in the actuator.
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Old 02-11-2014, 11:57 AM   #80
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Yeah its a mystery: this is a donor engine from a 2001 NB that was wrecked. it was really clean inside, everything was great. I never took the cam gear apart before last night, and nothing else on the engine appeared to be broken. So no idea

My "original" engine from this car is sitting in the corner of my garage, but its so fresh and clean and perfect that I don't even want to open it up or take anything off.

lol
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