Vanos Rebuild Start Hesitation

[BL92]

My Money is on ICV, See if you can borrow one to try before you buy
Also check the return line to sump is connected under the air box ( can mess up fuel trims )
Check your PCV isn't blocked, and crossover hose isn't cracked

By the way have you logged your AFRs? Windband gauges are a must for trouble shooting

[jamesfoley]

Someone on E46 Fanatics was having starting issues
He changed the ICV and it was all sorted

As far as I know the ICV is good. I did pull it out and clean it which made it move more freely. I'm not having any other drivability issues either, I know the car uses the ICV for low engine load intake which I would have thought would be jerky and horrible if the ICV was dead. Only time the car is kinda jerky is when the secondary air pump is active and engine cold, but have been told this is normal.

Only other thing I did want to note, and it sounds kind of stupid and unrelated, but when the car has its weird start, the steering wheel controls (volume and skip track) stop working. I have an aftermarket radio, so it might just be the canbus decoder thats getting upset, but did also think what if the canbus box is throwing junk down the k-line bus making other things upset? I don't actually know if there is anything vital to the car starting on k-line though, pretty sure it was just all entertainment / interior stuff.

[BL92]

Someone on E46 Fanatics was having starting issues
He changed the ICV and it was all sorted

[jamesfoley]

It has been a while, car still has its quirky start now and then, but it has never failed to start, and once started it runs and drives without an issue.

However every now and then the car throws codes even though there is no fault present. The main concern is “10 [015] Signal, cranksheft sensor” that keeps popping up on the DME as a shadow code.

Is the car trying to tell me there is actually something wrong with the crankshaft sensor / crankshaft signal wire, or is it possible for these to just appear and disappear at random?

Think I’ve mentioned this code before, and I have had the sensor swapped. Would be good just to understand if there is a problem there or not.

[jamesfoley]

On the graph you posted I see the cold start ex cam issue as I posted earlier: expected 15 degrees but actual is only 3, for a short duration but enough to be different than warm starting.

Both cold and warm start seem to be around the same, if you look at the Google Sheets spreadsheet of the values from that graph pretty sure line 8467 is where the engine is turned off with actual being set to 0 but expected being set to -10. Then line 9268 is warm start where actual is now -4.2 and expected is 9.5. Cold start has an actual of -1 and an expected of 12, you can see from my other cold start logs further up that I've also has -5 actual, 11 expected.

The numbers feel weird but can't tell if its normal or not. I figured there would have been a VANOS tables somewhere in the DME.

[sapote]

Not sure I understand what you mean. I was just saying that the exhaust actual and expected deviation is the same both cold and warm start.

Do you mean the exhaust cam expected should hold 12 degrees for longer than it does?

Is

On the graph you posted I see the cold start ex cam issue as I posted earlier: expected 15 degrees but actual is only 3, for a short duration but enough to be different than warm starting.

[jamesfoley]

Not the same: expected should be 12 degrees for some time but actually only get to 3 degrees

Not sure I understand what you mean. I was just saying that the exhaust actual and expected deviation is the same both cold and warm start.

Do you mean the exhaust cam expected should hold 12 degrees for longer than it does?

Is it possible to cross reference these values with a table from the MSS54 XDF?

I've tried checking the partial I pulled from my DME using TunerPro and the 1301 XDF, though a lot of the data is just jumbled so assumed there is something up with the 1301 XDF

[sapote]

Only because of the Y axis scale, the actual values are the same.

Not the same: expected should be 12 degrees for some time but actually only get to 3 degrees

[jamesfoley]

Cold start graph shows totally different than warm start

Only because of the Y axis scale, the actual values are the same.

[sapote]

Scales for the graphs are different, exhaust cam actual is -1 degree when expected is 12 degrees for some reason. They then align to 3 degrees, +/- a degree.

However the same discrepancy is there when the car starts normally, so I don’t know if it’s actually a problem, or if the car just starts easier when warm even with this cam position difference on the exhaust.

VANOS test proves there is nothing wrong with the timing as it reaches the expected positions without an issue.

Don’t know if perhaps my exhaust cam position sensor is just doing a shit job at reading the cam on engine start, though if it was the sensor I’d expect drivability issues somewhere.

Also don’t know if that’s just how the DME works for the version I have.

Cold start graph shows totally different than warm start.
Vanos test was done with warm engine and so it’s fine.
if the cam sensor is glitchy then you would have error codes

[jamesfoley]

Cold start ex vanos issue:
The ex expected is 3 degrees retard but the actual shows 50 retard. So the ex couldn’t advance from max retarded to 3 degrees retarded.

Scales for the graphs are different, exhaust cam actual is -1 degree when expected is 12 degrees for some reason. They then align to 3 degrees, +/- a degree.

However the same discrepancy is there when the car starts normally, so I don’t know if it’s actually a problem, or if the car just starts easier when warm even with this cam position difference on the exhaust.

VANOS test proves there is nothing wrong with the timing as it reaches the expected positions without an issue.

Don’t know if perhaps my exhaust cam position sensor is just doing a shit job at reading the cam on engine start, though if it was the sensor I’d expect drivability issues somewhere.

Also don’t know if that’s just how the DME works for the version I have.

[sapote]

Cold start ex vanos issue:
The ex expected is 3 degrees retard but the actual shows 50 retard. So the ex couldn’t advance from max retarded to 3 degrees retarded.

[jamesfoley]

Just a small update with some data I have.

Results of VANOS test, and adaptations taken with DIS:


Cold start with hesitation, graph of VANOS intake and exhaust actual and DME expected positions:


Warm car running, key off and then engine start again, car did not hesitate this time but still has weird 10 degree jump on the exhaust positions:


I also have a VANOS cam position log which was started just after the cold start graph. It seems that both cams do stick to the DME requested position with a degree or two of difference, so I think its working as expected.

There are a couple of rows I've highlighted in orange though where there is a 10 degree difference in the exhaust cam actual and expected, seems to be at engine stop and start.

https://docs.google.com/spreadsheets/d/1u9PBg3NKFgR7Bph15trebvIxyyKTSn6TYibcxIgrvok/edit?usp=sharing

The car did run super rough while it was testing the exhaust side of the VANOS which I'm assuming is expected as its fully advancing and retarding the cam?

[jamesfoley]

In 3 videos I see engine ran normal. The M3 doesn’t start up smoothly as non-M cars.

My previous M3 never did this, and this never happened before I had the VANOS done, so to me it doesn’t feel like it’s a normal thing…

[sapote]

In 3 videos I see engine ran normal. The M3 doesn’t start up smoothly as non-M cars.