VVEL issue, at my wits end
 

I have tried everything I can think of which I will outline below. I'm about to start researching how to keep AC and do HR heads or something.

Background info
Built bottom end, refreshed heads, JWT exhaust cams and springs

Issue 1
I CANNOT for the life of me get the VVEL position sensor voltages to match. Bank 1 is constant and no issue, Bank 2 reads 0.1v less. If i sync the voltages as per FSM with the car off the "VVEL angle" on bank 2 is off a few degrees. Start the car up and it will match the angles but the position voltage will be 0.1v less on bank 2


Issue 2
Dependent on the gear, it appears to be a load related issue to me, the car will lose power and air flow will drop on Bank 2's MAF. This only happens during WOT and will not happen under part throttle. 2nd gear it happens at around 7000rpm, 3rd gear around 6500rpm and 4th gear at 5500rpm.

Also of note, Bank 2's MAF will read between 0.3 to 0.6 volts higher until it falls off drastically.

Thing's I have done so far.

Toned out the wiring between both position sensors and the VVEL ECU (all good 0 ohm readings)
Replaced both VVEL ladders
Replaced both VVEL motors
Replaced both VVEL position sensors
Replaced the VVEL ECU

When replacing the VVEL ladders, I left the valve covers off, manually adjusted the VVEL control shaft to minimum position and set the position sensors to read 0.5V. This still resulted in Bank 2's actual angle being lower than Bank 1.

I don't want to keep throwing parts/money at it. Maybe this motor is just cursed? Anyone been through this before?

I think there was a thread here with a similar issue. His problem turned out to be the sensor 'wheels' on the cams, the ones with teeth. One was slightly deformed. JCHammond will know what the correct term for those 'wheels' are, I'd call them 'pickup wheels', but that is probably not correct. IIRC, the camshaft sensors are on the intake cams, the sensor wheels are what trigger those sensors. Bank 2's sensor wheel might be damaged. :twocents:

I think your overthinking it. You don’t have to have the same voltage reading for the VVEL to properly work. Spec is 500mV +- 48mV. The only thing that you’re actually doing is setting the position sensor at a certain voltage so the control module knows where the shaft is at, from there it will take actual values and adjust accordingly. Out of the 100 or so VVEL engines I’ve rebuilt doing the VVEL Position adjustment can yelps weird results. IE: the position sensor never has an in spec reading no matter what way you turn it...but most of the time the position sensors will read slightly different. long story short is that you successfully adjusted them so don’t sweat the voltage difference...check out the attachment and look at the sensor learn values. They differ but are in spec. The other values don’t match but the car operates perfect!

How did you set the VVEL sensor voltages? This needs to be done with the VVEL motors unplugged when it is first done. If you did it with the VVEL motors plugged in, I am not sure what needs to be done to correct it.

This could be it. I will reset them momentarily and see what happens.

Interesting. When I swapped the VVEL ECU the voltages were pretty much dead on under load and differed 0.05v at idle. This eventually reverted to the 0.1v difference after 20 mins of driving. However the power loss issue was still there even with the voltages closer.

I did use "known good" gears off the running motor i pulled out but I will pull the cam gear covers off to inspect.

So your power loss only happens under a load, noticeably on bank 2 per your maf reading. So let’s say you’re just cruising at 45 in third gear and you go WOT your power is fine until you hit a certain RPM range? Do you just instantly stopped accelerating and lose power or does it feel like someone’s cutting off air and it’s just choking itself out? Do you “reset” the motors before adjusting the sensors? Check out the attached..do you have access to a scan tool that can perform the vvel position adjust work support item like consult? Some good scan tools can. Did you mess with the vvel ladder control shaft nuts that change the lift of the valve?

I adjust them as per that fsm page and use ecutek to view the voltages

I did not adjust the vvel arms in any way.

All parts came off a known good motor and all values were as they are supposed to be.

The power is good up until 6500 in 3rd, the shut down happens higher up in the rpm range in the lower gears, it happens at 5500rpm in 4th, the island is too small to even try a 5th gear with pull.

Which is why I think it’s load dependent.

This might not be of any help, but did you check the VVEL relays? I have a friend that threw a ton of VVEL codes, and come to find out the relay was loose. I'm not sure how since the nissan relays have a tab to lock them in, but never hurts to try it.

When you do a pull what is your vvel control angle commanded vs vvel control angle actual 1/2 at the point of power loss, any large variation between bank 1 and 2? Could your fuel pressure be at fault since it happens under high load?

I have checked the relay is seated properly.


Here is what I have confirmed. Using a wrench to turn the vvel shaft to minimum position yields 0* vvel angle on bank one and 1.39* on bank 2. This includes adjusting the position sensors to see when the angle value starts to change.

Is my logic sound that I have ruled out any mechanical issue?

I have toned out the bank 2 vvel position sensor to the vvel ecu and all wires come back 0 ohms. I may have something else going on with the wiring harness but I haven’t tracked it down as yet.

Commanded and actual angles are within a degree of each other for both banks under WOT.

Fuel pressure is good, I have an innovate gauge in cabin to keep tabs on that. Airflow to bank 2 drops, the MAF shows decreasing voltage and the AFR sensor starts to read rich.

Sounds like you have a boost leak. I would test it if you haven't already.

Boost leak test is good. As much of a pain in the *** as that was to do.

So here is what I have found. With the VVEL cam manually adjusted to minimum lift position, hitting the stopper the lowest reading I could achieve is 1.39* VVEL angle, not 0*. So I went back to the sensor connector pins and did the resistance tests all over again as well as making sure I got the 5v signals. As I went to test for the 5v between pins 5 & 6 I got nothing. Testing between pin 6 and engine ground got me 5v.

So even though I toned out the vvel position sensor wires to the vvel ecu pins and got 0 ohms, it appears that pin 5 on the sensor (white wire) which is a ground has a break somewhere. I dunno how it toned to 0 ohms last time but toning it out to the engine grounds yielded infinit resistance on my multimeter where as pin 2 which is also a ground resulted in 0 ohms doing the same test.

I vampire tapped a supplemental ground on that wire and the readings with the car off and ignition on are where they need to be.

Unfortunately I wont be able to do a driving test for another 3-4 hours. I will report back.