Vanos Rebuild Start Hesitation

[Slideways]

VANOS was done at a well recommended shop that does them frequently which is what makes this a bit fuzzy. They've also taken the car back and checked timing and told me everything is fine, however DIS is saying the inlet cam is out, so I'm not really sure who to trust at this point.

Fuel issues wouldn't cause the VANOS to not adapt though right? The car behaves exactly the same as it did before having the fuel pump and regulator changed so I have no real reason to suspect them, unless I'm honestly that unlucky to get a new genuine equally failing pressure regulator. I have zero issues while the car is running also, I can take the car through the entire rev range and not suffer misfires etc, apart from the car being obviously down on power.

Ah, it sounded like all the work, VANOS and fuel parts, was done at the same time (typically would not recommend this). The only thing I can guess is that they damaged the Beisan intake piston seal during installation. On the VANOS test, does it pass the pressure test?

[jamesfoley]

Ah, it sounded like all the work, VANOS and fuel parts, was done at the same time (typically would not recommend this). The only thing I can guess is that they damaged the Beisan intake piston seal during installation. On the VANOS test, does it pass the pressure test?

The VANOS test fails at the first step almost instantly after getting the car to 1500rpm so I don’t have any other test results unfortunately.

[sapote]

On the VANOS test, does it pass the pressure test?

If you meant the leakage test - or timing holding test in x seconds -- then this test only performed after the command test which is failed right at the start. The DME can't tell the vanos oil pressure.

[jamesfoley]

Is it possible to pull up live VANOS data in INPA for the MSS54?

I can't seem to find anything related to VANOS in my copy of INPA.

[jamesfoley]

Still haven't got around to getting the VANOS timing looked at, but pulled these graphs using TestO. Both graphs plotted at the same time and taken during engine start, and the wobble in the "Actual" graph is the engine starting and struggling to idle. As soon as it flattens out past the 15 second mark the car runs fine.

Not sure why the "Expected" graph starts at 52.5, but this was the DME value in DIS for the inlet cam to get an actual reading of 60 degrees, so I'm assuming when the engine is off 52.5 degrees is the position its being left in and then it does some hunting of the correct timing when it starts next?

No idea if it actually shows / proves anything, but figured it might be worth just keeping it documented in the thread.

[sapote]

1. Still haven't got around to getting the VANOS timing looked at, but pulled these graphs using TestO. Both graphs plotted at the same time and taken during engine start, and the wobble in the "Actual" graph is the engine starting and struggling to idle. As soon as it flattens out past the 15 second mark the car runs fine.

2. Not sure why the "Expected" graph starts at 52.5, but this was the DME value in DIS for the inlet cam to get an actual reading of 60 degrees, so I'm assuming when the engine is off 52.5 degrees is the position its being left in and then it does some hunting of the correct timing when it starts next?

1. The graph shows the cam wobbling during starting; I think this was due to the engine rpm unstable (DME reads the crank angle in order to come up with this cam angle value), and not the vanos itself struggled.
2. I think you're right about the initila 52.5* at start up. The working spread angle for intake is [70 to 130*] relative to 0* at TDC, where 70 is advanced and 130 is retarded; at start, the intake should be retarded at 130 which is 60* in VANOS speaking (0* is most advanced at real 70* spread angle).

[jamesfoley]

Just as an update, I had the VANOS re-timed and the intake was a spline out which I guess was enough to put it out of spec. Car pulls so much better now that the VANOS is actually doing something.

Unfortunately still have issues with it starting. I realise that I put in the OP that I had the fuel regulator replaced, I have the part but it just hasn't been fitted yet. I think this is the last potential piece that could be causing me issues, either the fuel regulator itself, or the vacuum line between the regulator and the air rail.

[sapote]

JI had the VANOS re-timed and the intake was a spline out which I guess was enough to put it out of spec.

If it was off by a spline then there should be an error code as one spline is more than 10 degrees error.

[jamesfoley]

If it was off by a spline then there should be an error code as one spline is more than 10 degrees error.

Only error it ever threw was an inlet adaptation error, nothing else, and even then it took a while for the error to appear after clearing it.

[ATB88]

My car adopted a hesitant start after I re-timed my VANOS. Runs perfectly, absolutely no errors, but hesitates to start in a way that it never did before I did the VANOS, and once every few months it will fail to start just once (and then start perfectly on next attempt).

I have replaced *ABSOLUTELY EVERYTHING* that could be related -- every sensor, every ignition part, everything in the fuel system, never fixed it. I wonder if we've got the same ghost?

[jamesfoley]

My car adopted a hesitant start after I re-timed my VANOS. Runs perfectly, absolutely no errors, but hesitates to start in a way that it never did before I did the VANOS, and once every few months it will fail to start just once (and then start perfectly on next attempt).

I have replaced *ABSOLUTELY EVERYTHING* that could be related -- every sensor, every ignition part, everything in the fuel system, never fixed it. I wonder if we've got the same ghost?

I have come across your thread a couple of times and it has made me worry that this will never be solvable. From what I can remember the car never did this before I had the VANOS rebuilt, however I didn't have the car long before having it done as it was always the plan to get everything sorted as soon as I could. It is 100% possible that I bought the car with the issue and it just wasn't presenting itself at the time, which would be a little unfortunate. It can go a few days and start straight away first time, and then it will go a few days of consistently being upset about starting.

There are still a couple of bits I've been advised to change which its booked in for, the fuel pressure regulator and the vacuum line up to the air rail. If that doesn't work then I'll also schedule a clean of the injectors. Being a 2001 car with 120k on the clock there are a lot of rubber parts that are just falling apart, so I totally expect something to need replacing somewhere.

Out of curiosity did you try another DME?

[ATB88]

I have come across your thread a couple of times and it has made me worry that this will never be solvable. From what I can remember the car never did this before I had the VANOS rebuilt, however I didn't have the car long before having it done as it was always the plan to get everything sorted as soon as I could. It is 100% possible that I bought the car with the issue and it just wasn't presenting itself at the time, which would be a little unfortunate. It can go a few days and start straight away first time, and then it will go a few days of consistently being upset about starting.

There are still a couple of bits I've been advised to change which its booked in for, the fuel pressure regulator and the vacuum line up to the air rail. If that doesn't work then I'll also schedule a clean of the injectors. Being a 2001 car with 120k on the clock there are a lot of rubber parts that are just falling apart, so I totally expect something to need replacing somewhere.

Out of curiosity did you try another DME?

Yeah I mean it's been ~3 years for me at this point and I've learned to live with it. Doesn't affect performance, driveability, or reliability, is just annoying to know it doesn't have to be like this lol. I did try replacing the DME, no luck -- same behaviour on stock MSS54 DME and MSS54HP DME (with and without CSL airbox and associated tune). Also did FPR and vacuum line, and for injectors I initially tried cleaning, and then tried a totally fresh set since OEM Bosch was still available cheap back then. I hope you have a different experience, and/or somehow figure out something that I didn't!

[sapote]

VANOS was done at a well recommended shop that does them frequently which is what makes this a bit fuzzy. They've also taken the car back and checked timing and told me everything is fine, however DIS is saying the inlet cam is out, so I'm not really sure who to trust at this point.
....
Adaptation values in DIS for the VANOS come back with a DME commanded 52.5 degrees to reach an actual 59.9 degrees on the inlet, and the test fails with the inlet retard position at 69.4 degrees.
.......
Just as an update, I had the VANOS re-timed and the intake was a spline out which I guess was enough to put it out of spec. Car pulls so much better now that the VANOS is actually doing something.

You should call the shop manager on this -- either they lack the skill or lazy to verify their work. They set the Intake off by about 8* too retard. This means you never can have the full intake advance at higher rpm and so engine was low performance. Did you find the IN was too retard by one spline?

If the vanos timing was verified good, then the issue of hard cold starting maybe related to other things. Get a Veepeak OBD reader on Amazon ($31) and OBD Fusion app for phone ($15), then read the data in a log file with these data: MAF, engine temp, intake air temp, rpm, fuel bank status, stft and ltft, O2 sensor pre and post cat.
Do a log at hot engine idling and post it here.

[jamesfoley]

You should call the shop manager on this -- either they lack the skill or lazy to verify their work. They set the Intake off by about 8* too retard. This means you never can have the full intake advance at higher rpm and so engine was low performance. Did you find the IN was too retard by one spline?

If the vanos timing was verified good, then the issue of hard cold starting maybe related to other things. Get a Veepeak OBD reader on Amazon ($31) and OBD Fusion app for phone ($15), then read the data in a log file with these data: MAF, engine temp, intake air temp, rpm, fuel bank status, stft and ltft, O2 sensor pre and post cat.

Do a log at hot engine idling and post it here.

To be honest I'm not sure I can be bothered with the hassle bringing it back up with them. What's done is done, I'm dealing with another specialist now and there was no physical harm done, so just going to move on. Engine was indeed down on power and after having the timing sorted its all back, turns out exhaust rasp is about half as quiet with the VANOS not working.

I have a Scantool OBDLink MX+ along with the OBDLink app on my iPhone I can use to log, alternatively I could pick up a cheap Android tablet and use OBD Fusion or Torque Pro which I might do. I also have a laptop with INPA, DIS, P.A.Soft BMW Scanner, and TestO, so plenty of things to pull logs from. I can log what you've suggested without any issue but I'm not sure it'll flag anything, mainly because once the car is actually running it runs perfectly. The hesitation it has is purely when cranking the engine, and it can happen both cold or hot.

Either way I'll post some logs once I have them 👍

[jamesfoley]

sapote Not sure if this is of any use? Pulled this using OBDWiz and my OBDLink SX cable as I figured it might be a little more reliable than bluetooth.

https://docs.google.com/spreadsheets/d/1S39r-gle4AkVZQbz0lgBFSDoG0dpXlXvp6goGoDOJQk/edit?usp=sharing

That spreadsheet has 3 sheets in it. The first is the car setting off after faffing with the logs and some town driving. The second is just pure warm engine idle. The third is town driving again after leaving the car for 45 minutes.

Annoyingly it didn't suffer from any start hesitation, just started as normal. No idea why it goes through bouts of being fine, and then bouts of being upset. Sort of wondering if it's directly related to the weather with it being more temperamental when it's cold outside.

If I can pull any more logs which might be of use let me know.