Vanos Rebuild Start Hesitation

[oceansize]

Intake cam actual position compared to requested are exactly the same, but my exhaust cam actual vs requested are out by a degree. Exhaust values jump around all over the place and are never in sync.

Can 1 degree on the exhaust cam be the cause of the issues?

This was picked up by another specialist after confirming fuel pressure was good.

No issues, can be off by as much as eight degrees so you are fine.

[jamesfoley]

No issues, can be off by as much as eight degrees so you are fine.

I think they were more saying that even after adaptation, the DME requested position never matched the actual position. So even though it it was requesting 0 degrees, actual position was coming back as 1 degree. I thought the adaptation values were meant to correct errors in requested vs actual to make them match?

Both intake requested and actual positions are exactly the same to the decimal place, so kind of assumed exhaust would be the same too. Wondered if it was this that was confusing the DME where the exhaust side of the VANOS is not left in the position it is expecting it to be when the engine is turned off, giving me the extremely random start hesitation depending on where the cam position is.

[oceansize]

I think they were more saying that even after adaptation, the DME requested position never matched the actual position. So even though it it was requesting 0 degrees, actual position was coming back as 1 degree. I thought the adaptation values were meant to correct errors in requested vs actual to make them match?

Both intake requested and actual positions are exactly the same to the decimal place, so kind of assumed exhaust would be the same too. Wondered if it was this that was confusing the DME where the exhaust side of the VANOS is not left in the position it is expecting it to be when the engine is turned off, giving me the extremely random start hesitation depending on where the cam position is.

Variances are common even after adaptations and the command vs actual is fine to mismatch while driving. 98% of the time the variances are within two degrees on my car. Get spikes where they can be greater.

The commanded values at idle should be:

intake: 60
exhaust: 0

[jamesfoley]

Variances are common even after adaptations and the command vs actual is fine to mismatch while driving. 98% of the time the variances are within two degrees on my car. Get spikes where they can be greater.

The commanded values at idle should be:

intake: 60
exhaust: 0

Are mismatches expected at idle though? Inlet cam was rock solid 60 degrees with no variance, exhaust was flickering around a couple of degrees constantly almost like it was trying to adapt for the difference between commanded and actual but never being able to get them equal.

Is TestO the only tool I can graph the cam positions? Pretty sure the guys I saw used an Autel scanner which could graph stuff, but they're expensive it seems

[oceansize]

Are mismatches expected at idle though? Inlet cam was rock solid 60 degrees with no variance, exhaust was flickering around a couple of degrees constantly almost like it was trying to adapt for the difference between commanded and actual but never being able to get them equal.

Is TestO the only tool I can graph the cam positions? Pretty sure the guys I saw used an Autel scanner which could graph stuff, but they're expensive it seems

Been a while but it seems like it is fine for the exhaust to fluctuate a bit while intake hangs steady, but perhaps someone else can confirm as it has been a year or two since I last data logged and took note. I have AutoEnginuity but it isn't cheap.

[sapote]

Intake cam actual position compared to requested are exactly the same, but my exhaust cam actual vs requested are out by a degree. Exhaust values jump around all over the place and are never in sync.

Can 1 degree on the exhaust cam be the cause of the issues?

This was picked up by another specialist after confirming fuel pressure was good.

If the DME doesn't issue error code for the EX cam then it's acceptable. If the cam timing is bad enough to cause issue, then DME should have popped the codes.

[jamesfoley]

If the DME doesn't issue error code for the EX cam then it's acceptable. If the cam timing is bad enough to cause issue, then DME should have popped the codes.

I guess the only issue I have is that the DME doesn't seem to like throwing codes for anything 😅

Other than timing, is there anything else hidden in the VANOS that could cause issues and not present a code? I've read a couple of posts now of people who have had issues after a rebuild and mention wear on VANOS internals as a potential. There is also oil pressure at the VANOS which I could probably check? Suppose there is also the potential that there was an issue with the seal install

[jamesfoley]

Just to follow this up with a bit of data, here is a log of Inlet and Exhaust commanded vs actual positions. Pretty sure the Exhaust graph just looks bad due to scaling but the Exhaust position swings half a degree above and below the commanded, and Inlet swings up to a degree below commanded. TestO is pretty decent when it doesn't crash.

My only question is what are the "banks" it is referring to here?

[Tomba]

My only question is what are the "banks" it is referring to here?

MSS54 is near to equal as MSS52 (used for S62) As S62 is V8 engine and has 2 banks and double VANOS these are used.

You have TestO, do you also have Tool32?

[jamesfoley]

MSS54 is near to equal as MSS52 (used for S62) As S62 is V8 engine and has 2 banks and double VANOS these are used.

You have TestO, do you also have Tool32?

I figured it might have been for engines with multiple inlet/exhaust cams. Only reason I ask is the Exhaust bank 2 has an actual value that changes? Where it gets that reading from I have no idea...

I have EDIABAS ToolSet 32, assuming that's the same thing?

[sapote]

“guess the only issue I have is that the DME doesn't seem to like throwing codes for anything 😅”

I suggested to reflash or replace the Dme before.

[jamesfoley]

“guess the only issue I have is that the DME doesn't seem to like throwing codes for anything 😅”

I suggested to reflash or replace the Dme before.

Issue I have with buying a new DME is that they're expensive to begin with, and then I need to find someone to either clone my DME, or do an EWS delete. So overall it would be an expensive experiment

[Tomba]

I can flash your DME remotely if you want. We can make a copy first and then flash latest software to begin with.

[jamesfoley]

I can flash your DME remotely if you want. We can make a copy first and then flash latest software to begin with.

Appreciate the offer. My laptop just about runs INPA without dying, so trusting it to flash my DME with someone logged in remotely is a big ask 😅

Car is hopefully getting booked back in for another VANOS timing triple check, I have an oil leak from where the VANOS meets the head so it needs to come off to change that seal anyways.

I'll look into picking up a better laptop I can use and then maybe hit you up Tomba

Did just have another thought though, I don't suppose it could be EVAP related seeing as basically everyone I take it to said it sounds like fuel? I've seen the DMTL pump mentioned in some threads but as far as I know my car doesn't have this, just the activated charcoal filter. There is the fuel tank breather valve though that connects to the same pipes as the ICV...

[Tomba]

Why check everything again when you can do it with a VANOS test I made for Tool32?

https://nam3forum.com/forums/forum/special-interests/coding-tuning/34304-need-help-doing-vanos-test-with-inpa?p=35697#post35697

Also, reading the ECU with a small program won't affect your laptop. But we do can check if the calibration is untouched or modified.

http://www.msstuning.com/mssflasher.html

For the DMTL/EVAP. If these valves leak when closed, fuel fumes could enter the manifold when standing still and have bad starting issues as a result.