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Hello guys. For more than a year, my built 2002 engine has made a rattle from the head between 3000RPM and 4000RPM and about 10in of vacuum. It never bother me enough to look into it. I figured one of the valves may not have be shimmed perfectly from the rebuild. Last week, when starting the engine cold the idle was very rough. Investigation found the intake cam was not retarding as much as the ECU requested. At idle my cam target is -22* but the actual cam position is -16*. The cam advances as expected. For instance if the target is -15*, -10* or +10* the actual position matches the target +/-0.5*. It just will not go farther negative than -16*
I did some research and immediately found Curley's write up about rebuilding the actuator. I also found a few other posts and some videos on You Tube covering rebuilding the actuator. However, has anyone rebuilt an actuator and then have it work or not rattle any longer? I have not found any threads were someone had an issue with their actuator, rebuilt is and solved the issue.
There's really nothing to go wear out or cause it to rattle unless it's been opened previously and not reassembled properly. Solenoid is controlled with a modulated pulse width to deliver a range of oil pressure to a spring loaded lock pin that allows the cam to rotate when un-locked. There are 4 inner and 4 outer spring loaded "apex" seals to keep the center rotating assembly centered. Miata Roadster's VVT rebuild kit includes the two large o-rings to seal either side, and the 4 small ones to go under the 4 m6 bolts that hold it all together. No inner rotating parts though.
Thanks Curly. No, it has never been apart in its life, 66K miles. I've pretty much decided I'm going to open it up to see if something is in the mechanism causing the rattle and/or keeping it from moving to the full retard position.
Thanks Curly. No, it has never been apart in its life, 66K miles. I've pretty much decided I'm going to open it up to see if something is in the mechanism causing the rattle and/or keeping it from moving to the full retard position.
I removed and opened up my VVT Actuator this afternoon. From the findings on the cam position relative to the target, I expected to find debris is the mechanism. No such luck. When the cover was removed, the mechanism was locked at full retard. After disassembly the only odd things i found were, one of the "apex" seals remained in the groove as if it had no spring tension forcing it out against the rotating center piece. Second was obvious marking on the center piece where the locking pin tried to engage when the cam was not at full retard. Photos are below.
I'm not sure where to go from here. I have Miataroadster's o-ring kit on the way. I guess I reassemble and hope for the best. If that does not work, new actuator?
Stuck Apex Seal
No signs of scrapping from the center piece as it rotated through its range.
Mark from locking pin trying to engage when cam was advanced. How do I fix this?
A few more of the actuator housing with no flash. Everything I see looks like normal marks from the manufacturing process. But if you see something I do not, please let me know.
Another picture of the center piece. Marks can be seen in this image.
A bit more information to aid in trouble shooting. The engine was rebuilt about 7K miles ago with a BE oil pump. I got one with the shitty front oil seal, YAY! The car is not a daily driver, but gets driven regularly. The longest it every sits is about 2 weeks at a time. I added a real VDO oil pressure gauges with the sender mounted in my remote oil filter housing. The OEM oil pressure switch is wired to a super bright LED in the dash. After several days of sitting I notice about 1 to 2 seconds of rattling from the top end, 0psi on the gauge and the LED illuminated before pressure is made. Then, my gauge goes to 90psi and everything quiets down. Hot idle pressure is never below 40psi.
With the addition of the hoses to the remote oil filter housing, have you made any provisions to keep the oil from draining all the way back to the pan?
An anti-drain-back valve in the filter may not be sufficient.
I rebuilt the VVT actuator over the weekend an installed all the Viton O-rings from the Miataroadster VVT rebuild kit. I figured the only thing I had to lose was installation time. If the actuator did not work, I would buy a new or used one and put it on. Took the car out for a drive tonight. Upon initial startup, the engine idled smoother. Moving the cam by changing the cam position setpoint at idle showed the cam now reached several settings from full retard to 10 degrees advance. The idle was really bad at that +10 degrees. Took the car out for a drive and it worked just fine. The cam moved smoothly to the setpoint dictated by the 3D map at all engine speeds and boost levels. Acceleration at medium throttle openings felt brisk. I made a few WOT runs at my base boost level set by the WG actuator and the boost level was 1psi higher than before. Switching to my EBC level of 15psi resulted in the engine hitting the over-boost protection set at 20psi. Interesting. It appears the engine is flowing more air then is has in quite a while. I had not looked at cam position for many years because after initial setup when installing the Hydra and playing with a few profiles, I never thought about checking it again. I have to assume the VVT actuator, or the control solenoid, have have not been working properly for quite some time. All seems to be working very well now. I'm going to try to get back on the dyno this weekend to see if I have picked up any power and to get the fuel and ignition tables dialed in.
I still have one issue. At about 10" of vacuum between 3000 and 4000RPM, I get a rattle from the top end of the engine. In this operation area the cam is advanced by 10 to 12 degrees. I now think the sound is coming from the VVT actuator were the locking pin is being pushed against the internal portion of the actuator that connects to the cam. A mark from this can be seen in one of the photos above. However, I can not get my hands on a document or diagram that shows the VVT system operation. Why does the system have a locking pin? What determines when it gets pushed into the bushing? I have tuned several VVT engines with Hydras with the same settings as in my car, and none of them exhibited this behavior. Puzzling.
11-05-2017, 06:54 PM
VVT Actuator Rebuild
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