valvetronic Motors-Steppers Or? How to Test

[cfoss]

Hey all.

I believe I have an issue with the valvetronic motor on bank 2 of my N62 4.4 V8.

Is it a stepper motor or jut a regular brushed dc motor? I've read conflicting accounts.

Can I test it by removing it and applying +-12VDC?

Thanks,

Chay

[aureliusmax]

Originally Posted by cfoss

Hey all.

I believe I have an issue with the valvetronic motor on bank 2 of my N62 4.4 V8.

Is it a stepper motor or jut a regular brushed dc motor? I've read conflicting accounts.

Can I test it by removing it and applying +-12VDC?

Thanks,

Chay

You need a special stepper motor driver tool. I haven't actually tried it out, but I do have the driver tool and three spare motors, if you're interested I could sell you the tool or some spare motors. Also have a spare valvetronic module.

[andrewwynn]

I think they are identical parts the go to method of that's the case is swap and see if the problem migrates.

[cfoss]

Sooooo,

I pulled the driver side motor-I'm getting misfires on 6,8 (at least that's what bmw scanner 1.4 says).

I also did more research. It seems the valvetronic 1,2 are standard motors, and valvetronic 3 uses stepper motors and doesn't use position sensors.

If you apply +-12V the motor will spin one way, then the other.

The driver one seems to work well. I will test it by bolting it on to the cam assemble and testing it under load there.

Ok, on to a more general question....I'm getting misfires on 6,8 after doing the valve seals (And all the valve cover seals also).

Initially, when I did the motors, I did not follow the wind down procedure and there was bit of popping on the motors upon removal.

On first startup, the engine ran poorly. WTF! I read about finding the upper and lower limits on the assembly, but I don't have inpa or insta, so until I do, I can't get this done. I did do the 10 gas pedal thing at key on run, and also let it sit for 15 minutes in run...What do you know...it started and idled great. It had a bit of a hesitation when you come to a stop occationally...like a hiccup but not bad.

But, it had a coolant leak, and in the time it took to fix that, the battery died and now it has misfires again.

How do I check for signs of intermediate shaft damage, other than the gear teeth (Which appear in very good shape)?

I'm starting to think about swapping an LS and being done with this overly complicated engine management system! (Maybe with a 4 barrel carb lol).

Thanks

Chay

[80stech]

I'm thinking in order for the valvetronic to cause a miss on 6 and 8 it has to be not opening valves on those 2 cylinders the same amount so the problem is unlikely to be with the motor or anything in common with all cylinders. That being said, I would make sure of spark plugs, coils compression, injectors, vacuum leaks etc. before blaming the valvetronic/valve lift. If it does come to that you could try to adjust the valvetronic manually or maybe adjust the minimum air flow at the throttle body or IAC if it has one.
I've never worked on these though, just my 2 cents on how I would approach it.

[cfoss]

Aha, good comment.

One test I did was to disconnect the motors and position sensors, then crank the motors all the way to valve open using the 4mm allen key.

This is supposed to make the engine run, while controlling the airflow with the throttle body.

It did run, more smoothly at first, then the miss came back. In general it did not run very well.

This would tend to indicate that the valvetronic is not at fault, as you have suggested. I'm just trying to do a process of elimination to get to the root of the issue.

A couple of other things I noted. I reset the valve lift to minimum on both banks, then reconnected the sensors.

I connected a 12V test light to the drivers side bank, and turned the ignition to run. I had read that the motor should try to go to full open then closed to learn the range each time the engine is started. That didn't happen. The light did not illuminate at all. However, when I crank the engine, the light came on indicating some movement was being called for.

It seems there is a lot of misinformation out there on this system, or perhaps info that pertains to one version or other but not all of them.


The spark plugs look fine-haven't tested them yet. It would be very strange for them to work, then not work, then work again. I will check them soon.

I figure I'll do my best to check the lift system, then start moving forward.

While I have the valve cover off I'm going to rechech the cam allignment, although one would have to guess that would affect the whole bank as well.

I did a leak down test before I started to see if the engine was worth working on. the results were very very good.

I could recheck but It's unlikely anything has changed.


Chay

[80stech]

You can't assume compression etc. is all good because it was before you did the valve seals, wouldn't be the first time a piece of carbon got knocked loose and burned a valve or got caught on a spark plug etc.

[cfoss]

Well I spent another interesting day on the bmw.

I did a leakdown test on the engine just to confirm it's all ok. I set both banks to max valve open just for fun. I cranked each cylinder to 80 psi. Here are the results:

Cyl 1 76
Cyl 2 76
Cyl 3 76
Cyl 4 77
Cyl 5 76
Cyl 6 77
Cyl 7 76
Cyl 8 77

So, very very good in other words.

Then I had an idea on how to check the valve lift mechanism: Rotate the engine so that the intake cam lobe is at max and then rotate the valvetronic motor from the valve closed stop to valve open on each cylinder and see if they are similar.

The way I did this is to use the leak down tester, set to about 20psi input. This is not enough to rotate the engine, but is enough to determine when the valve opens.

I have read that the valves will be open a tiny bit even when the lift is at minimum, but my valves are closed at the minimum stop-so the test worked.


Here's a vid of how I did it:

https://www.youtube.com/watch?v=eQ0ptrnwz5A

The four valves were very similar:

Turns before open:

Cyl 5: Crack: 1.5, Open: 2.0
Cyl 6: Crack: 2.0, Open: 2.5
Cyl 7: Crack: 1.5, Open: 2.0
Cyl 8: Crack: 1.0, Open: 1.5


So it seems the cylinders are pretty synched. Looks like mechanically the valvetronic lift mechanism is fine.

Onward....

Next up, I'm going to check that the cams are still in time with the engine with the allignment tool. I expect that they will be fine, but while I'm here I may as well eliminate that possibility.


Chay

[aureliusmax]

Originally Posted by cfoss

Well I spent another interesting day on the bmw.

I did a leakdown test on the engine just to confirm it's all ok. I set both banks to max valve open just for fun. I cranked each cylinder to 80 psi. Here are the results:

Cyl 1 76
Cyl 2 76
Cyl 3 76
Cyl 4 77
Cyl 5 76
Cyl 6 77
Cyl 7 76
Cyl 8 77

So, very very good in other words.

Then I had an idea on how to check the valve lift mechanism: Rotate the engine so that the intake cam lobe is at max and then rotate the valvetronic motor from the valve closed stop to valve open on each cylinder and see if they are similar.

The way I did this is to use the leak down tester, set to about 20psi input. This is not enough to rotate the engine, but is enough to determine when the valve opens.

I have read that the valves will be open a tiny bit even when the lift is at minimum, but my valves are closed at the minimum stop-so the test worked.


Here's a vid of how I did it:

https://www.youtube.com/watch?v=eQ0ptrnwz5A

The four valves were very similar:

Turns before open:

Cyl 5: Crack: 1.5, Open: 2.0
Cyl 6: Crack: 2.0, Open: 2.5
Cyl 7: Crack: 1.5, Open: 2.0
Cyl 8: Crack: 1.0, Open: 1.5


So it seems the cylinders are pretty synched. Looks like mechanically the valvetronic lift mechanism is fine.

Onward....

Next up, I'm going to check that the cams are still in time with the engine with the allignment tool. I expect that they will be fine, but while I'm here I may as well eliminate that possibility.


Chay

Clever. I have discovered a way from software to eliminate the valvetronic and force the engine load control through the throttle body. It's temporary for a drive cycle. I've been driving the car for 30,000KM this way without any misfires. I finally found a wrecker engine and replaced the camshafts on the cylinder bank that showed visual wear on the exhaust and intake lobes, so I don't need to carry the computer with me every time to use the car. There's a russian guy that makes an android-app with the common cheap bluetooth obd adapters that runs the same code, but you don't need a computer, tool32, and an adapter.

But your original post is strange. You didn't describe what your fault is. Otherwise I would have mentioned something. I thought you were just curious on how to test the motors.

[cfoss]

Thanks for the info. I may hit you up for more on that if I can't get this thig to work.

I try not to bore people with long winded stories about this project. It's my daughter's bmw. In canada, you have to import vehicles from one province to another-this requires an inspection. I'm trying to get the vehicle good enough to pass. It was running fine, but had the typical valve seal problem found on these engines.

I pulled the cradle, fixed the valve seals (Which were absolutely awful), and upon reassembly it has a misfire-then it went away, now it's back. Super weird. So I'm trying to locate a fault which is intemittent-always a fun job.

I'm just picking away at issues that could lead to misfire. What lead me to believe it was valvetonic related was that I tried one of the 'fixes' for the valvetronic system which is to leave the ignition on for 15 minutes then try again...Like magic the misfire was gone so I thought the issue is valvetronic related.

However, trying this approach again did not fix the misfire when it came back, so I thought I'd dig into it.


See, long story.

Anyway, some progress last night. I checked the intake and exhaust cam timing-they are 100% right on. I'm now reassembling the drivers side valve cover etc.

I'm also trying to get a copy of INPA working so I can get some insight into this system. I'm trying to find the BMW PassthroughD but its nowhere....very frustrating!

************************************Anyone have a copy they'd be willing to share??******************************************* *****


Thx,

Chay