Vanos Rebuild Start Hesitation

[jamesfoley]

I've had my VANOS rebuilt by a local shop using the usual Beisan parts, but since then have had an issue with the car hesitating to start, or just stalling instantly after catching.

Couple of people told me its likely a timing issue so the car went back to have timing checked and everything came back okay, but the car still has issues, so started going down the route of spark and fuel.

For what its worth the car has been throwing zero fault codes.

Here is a list of what I've one in the order I did them in:

• Inspection 2 including clearances
• Replace all ignition coils (Delphi)
• New fuel pump relay (OEM)
• New fuel pump (OEM)
• New fuel pressure regulator (OEM)

So did those over a month with no change to the starting. After a month though I'd noticed the car was very flat power wise, and the car also suddenly threw a DME fault, 94 Inlet Vanos adaptation, so I fired up DIS and instantly saw its not adapting at all on the inlet cam.

After being reassured the timing was good I figured it was going to be the valve body / coil pack, so threw a new genuine VANOS valve body and solenoid pack on the car and I get the exact same readings in DIS. The car also instantly fails a VANOS test stating the inlet cam position is "outside the tolerance band".

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. Resetting the adaptation values in the DME allow me to clear the fault code, and the car does seemingly drive okay, but it still just comes back with the same results in DIS.

Is this simply a case that the VANOS timing on the inlet cam is roughly 9 degrees out which puts it too far out to adapt? Also, does this mean my VANOS unit is basically not doing anything?

I started to wonder if the inlet cam sensor was failing but yea, I have no codes and consistent positions in DIS. Sort of expected a sensor to either not work or just be throwing random values everywhere. Was also starting to wonder about the impulse wheel on the end of the cam, but again the results I get in DIS are consistent.

Would the inlet cam being out of time also be the cause of the intermittent start hesitation? I don't know if perhaps the VANOS has to hunt for a 60 degree position on the inlet cam every time the car starts if it cant adapt. For what its worth the exhaust cam adapts fine and looks good.

Any help would be greatly appreciated.

[maupineda]

Seems like a timing issue. When testing VANOS, what are your speed and leak values?

[jamesfoley]

Seems like a timing issue. When testing VANOS, what are your speed and leak values?

Are these separate tests from the main tests? I've only got as far as pulling VANOS adaptation values, and then running the main test which just gets the car to 1500rpm, sees 69.3 degrees and instantly fails.

I've only really touched DIS to look into this issue so I'm not overly familiar with the software.

[maupineda]

Are these separate tests from the main tests? I've only got as far as pulling VANOS adaptation values, and then running the main test which just gets the car to 1500rpm, sees 69.3 degrees and instantly fails.

I've only really touched DIS to look into this issue so I'm not overly familiar with the software.

No, they are all part of the test routine. I see now your test fails quickly. I would say is timing or the sensor is just bad. Start with the sensor as that is the easier/cheaper part. For timing, if you have the garage to check again, be there to see for yourself the car is indeed timed correctly.

[jamesfoley]

No, they are all part of the test routine. I see now your test fails quickly. I would say is timing or the sensor is just bad. Start with the sensor as that is the easier/cheaper part. For timing, if you have the garage to check again, be there to see for yourself the car is indeed timed correctly.

Out of curiosity, is it even possible for the inlet cam sensor to be faulty like that and not have the DME store any fault codes? From everything I've read I feel like I should at least see something. Replacing that sensor looks like its a huge pain in the arse.

As for watching the engine get timed, I'm not sure I really know enough to know its being done correctly.

[Slideways]

How regularly does the shop do S54 VANOS rebuilds? Cause it sounds like they either didn't install the splined gears to get the maximum adjustment or they swapped the intake and exhaust splined gears. Other than that, a fueling issue, such as a failing fuel pump, almost always does not cause a DME error code. If this turns out to not be a timing issue, it might be best to check the fuel pressure and the recently installed fuel pressure regulator.

[jamesfoley]

How regularly does the shop do S54 VANOS rebuilds? Cause it sounds like they either didn't install the splined gears to get the maximum adjustment or they swapped the intake and exhaust splined gears. Other than that, a fueling issue, such as a failing fuel pump, almost always does not cause a DME error code. If this turns out to not be a timing issue, it might be best to check the fuel pressure and possibly question the recently installed fuel pressure regulator.

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.

[maupineda]

A friend of mine recently had issues with VANOS failing to adapt. When they undo it, found the hub spring washers were installed incorrectly. You seem to have a hardware issue.

in his case the cup washer was flipped so the cam was stock. Similar to what you are experiencing

[jamesfoley]

A friend of mine recently had issues with VANOS failing to adapt. When they undo it, found the hub spring washers were installed incorrectly. You seem to have a hardware issue.

in his case the cup washer was flipped so the cam was stock. Similar to what you are experiencing

Fair, sounds like I either need to go back to the shop again and get them to pull it apart, or cough up some more cash and have another shop re-build it again.

Going to assume that if DIS says the timing is out, then its likely the timing is actually out rather than something else being faulty?

[sapote]

I've had my VANOS rebuilt by a local shop using the usual Beisan parts.

which parts they replaced?

all ignition coils (Delphi)
After being reassured the timing was good I figured it was going to be the valve body / coil pack, so threw a new genuine valve body and coil pack
.

what valve body/coil pack? Do you mean the vanos solenoid plate or the ignition coils again?

No where I see report of the vanos measured oil pressure. The new Beisan pump disc/pistons can caused low pressure with parts not in tolerance. With low pressure dynamic cam timing will be wrong.

[jamesfoley]

which parts they replaced?

As far as I know it was the seals, anti rattle kit, and a re-drilled oil pump disc. Rebuild was done as it was done previously using shims on the oil pump disc that were backing out.

Invoice lists timing chain tensioner pad, uprated cam bolts, uprated diaphragm springs, seal kit, anti-rattle kit, and re-drilled oil pump disc.

what valve body/coil pack? Do you mean the vanos solenoid plate or the ignition coils again?

No where I see report of the vanos measured oil pressure. The new Beisan pump disc/pistons can caused low pressure with parts not in tolerance. With low pressure dynamic cam timing will be wrong.

Sorry I meant valve body and solenoid pack, part number 11367839180 specifically brand new from BMW.

I'm assuming you mean oil pressure taken directly from the top of the VANOS itself?

[sapote]

1) As far as I know it was the seals, anti rattle kit, and a re-drilled oil pump disc. Rebuild was done as it was done previously using shims on the oil pump disc that were backing out.
2) I'm assuming you mean oil pressure taken directly from the top of the VANOS itself?

1) re-drill your original disc or something else? Oil pump disc has no shims so I don't understand this. Disc cannot back out unless the pistons jumped off the larger OD roller bearing when hub tabs broke.
2) Yes, the pressure at the metal pipe on top of vanos.

[jamesfoley]

1) re-drill your original disc or something else? Oil pump disc has no shims so I don't understand this. Disc cannot back out unless the pistons jumped off the larger OD roller bearing when hub tabs broke.
2) Yes, the pressure at the metal pipe on top of vanos.

The original disc had the holes shimmed to reduce the play in the holes from a previous vanos rebuild, these thin shims were backing out of the holes on the oil pump disc. Had no broken hub tabs, but you could see the shims coming out of the holes with the valve cover off. As far as I know it was a redrilled disc from elsewhere, so not my original disc, just another pre-drilled S54 VANOS disc.

I've not taken pressure readings no as honestly I already feel like this is a little over my head at this point. Not really mechanically inclined, just putting together VANOS knowledge I've picked up from the hours of crawling the web trying to find a solution 😅

[sapote]

The original disc had the holes shimmed to reduce the play in the holes from a previous vanos rebuild, these thin shims were backing out of the holes on the oil pump disc. Had no broken hub tabs, but you could see the shims coming out of the holes with the valve cover off. As far as I know it was a redrilled disc from elsewhere, so not my original disc, just another pre-drilled S54 VANOS disc.

I've not taken pressure readings no as honestly I already feel like this is a little over my head at this point. Not really mechanically inclined, just putting together VANOS knowledge I've picked up from the hours of crawling the web trying to find a solution 😅

Never guessed that someone shimmed the holes with less than 0.5mm thick sleeves -- a bad idea.
The shop rebuilt the vanos should check the pressure after their works. It is like checking the engine compression after a rebuild.

[jamesfoley]

Never guessed that someone shimmed the holes with less than 0.5mm thick sleeves -- a bad idea.
The shop rebuilt the vanos should check the pressure after their works. It is like checking the engine compression after a rebuild.

As soon as I found that out I felt like I was driving a ticking time bomb, turns out finding an M3 with a VANOS rebuild invoice doesn't mean it was actually done well, but at least it was working at that point...

I have zero idea if the shop checked the pressure if I'm honest. The car is booked to go to my local BMW main dealer just because I was going around in circles with local garages trying to find the start hesitation, but now I've found this I'm tempted to find a specialist for a second opinion on the VANOS.