Vanos Rebuild Start Hesitation

[jamesfoley]

Bentley manual says this:

Ignition timing is electronically mapped and not adjustable. The ECM uses engine load, engine speed, coolant temperature, knock detection and intake air temperature as the basic inputs for timing control. A three dimensional map similar to the one shown is digitally stored in the ECM.

So unless there is an issue with the DME I’m not sure how fuel status would change ignition timing.

Knock counters don’t report anything, and temperature sensors appear to be fine, so I’m just a little bit confused.

Also just found this in the Bentley manual:

Traction control also comes into operation during deceleration. Decelerating on snowy or icy road surfaces can lead to rear wheel slip. If a rear wheel starts to drag or lock up, the ASC system can limit the problem by adjusting throttle, fuel injection and ignition timing.

Ironically the week before I had the VANOS done one of my rear reluctor rings cracked and I lost ABS, traction, and my speedo didn't work. Ended up driving to get the VANOS done with the dash lit up like a Christmas tree and no speedo. Had a new reluctor ring fitted along with a new ABS sensor at the same time the VANOS was done, which did fix all the faults. Just sort of made me wonder if the traction system is pulling timing / cutting fuel randomly, though I don't have the dash light flash or anything so probably not related.

[jamesfoley]

No, not tested anything related to the gear position. Both open loop faults and ignition timing drops happen at idle in neutral so I don’t think it can be gear position related.

I don’t know if I’m seeing the ignition timing drop because it’s going open loop, or if it’s going open loop because there is an issue with ignition timing.

[sapote]

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Fair enough, not even sure how I'd test either of those if I'm honest.

Did you test these parts? I think using INPA you can read the status of these components -- close/open, gear engaged/neutral

[jamesfoley]

Sorry for resurrecting this thread, but although I've sort of lived with this for a while I think I still have issues.

I have an OBD log which I included ignition timing on along side fuel system status and throttle position and can see that almost every time I have the fuel system go into open loop fault, my ignition timing drops close to 0 or sometimes negative.

https://datazap.me/u/jamesfoley/e46-m3-2?log=0&data=1-2-3-4

Is anyone able to explain what might be happening here, or if this is normal?

[jamesfoley]

Manual tranny have GPS and SMG don't (but the shift rod actuator does have the position encoder which provides the same needed information as GPS for the DME).

Fair enough, not even sure how I'd test either of those if I'm honest.

[sapote]

I've a manual car so not sure if I have a gear position sensor?.

Manual tranny have GPS and SMG don't (but the shift rod actuator does have the position encoder which provides the same needed information as GPS for the DME).

[jamesfoley]

One of the function of the clutch sw and GPS is to let the DME know when car coasting in gear and cut off injectors without causing stalled engine. If DME doesn't know it is coasting in gear with engaged clutch then it doesn't cut off injectors then this could be your fuel status 8 issue.

I've a manual car so not sure if I have a gear position sensor? Car is also Euro, so I don't need to press the clutch to start the car, unsure if this changes anything but searching about I can only find stuff that links the clutch switch with cruise control.

Some extra unfortunate news is that the car started hesitating on start again today, so I had a good 4 days after the head was rebuilt. LTFT's are 5% negative now with the same fuel system status 8 readings sprinkled about. I tried logging throttle position against it to see if it was instead throttle close that was triggering it, but I can't really see a pattern, it matches up with RPM drop more than throttle position.

I guess even though bent valves is a problem, it and the VANOS weren't the source of the starting issue.

Starting to feel more and more like its the DME tune messing with fuel delivery...

[sapote]

The GPS and clutch switch I’m not sure about, what does these actually do that would interfere with open / closed loop? I have fully working cruise control so I’d imagine they are both fine.

One of the function of the clutch sw and GPS is to let the DME know when car coasting in gear and cut off injectors without causing stalled engine. If DME doesn't know it is coasting in gear with engaged clutch then it doesn't cut off injectors then this could be your fuel status 8 issue.

[jamesfoley]

Are you saying the engine start hesitation problem was due to the bent valves?

So far every start has been perfect so it’s probably safe to assume the valve was the issue. I’m guessing it was something to do with what cylinders were trying to fire when starting based on where the engine was left when shut off. If you was trying to start on or close to cylinder 5 in the firing order then it would basically misfire due to leak.

Although saying that both the VANOS timing and valve shims were wrong which could have also been the cause. It seems to be important that this is 100% correct otherwise you're just going to have issues either with running, or bending a valve like mine did.

I would look at the the clutch switch and GPS, or tune software

The GPS and clutch switch I’m not sure about, what does these actually do that would interfere with open / closed loop? I have fully working cruise control so I’d imagine they are both fine.

Also I have no idea how I realistically check to see if my DME has a map on it that is different to factory. Maybe it’s worth putting the Evolve map on it or something?

[sapote]

Bit of an update to this. Car is back with me now after just over two months. Long story short is the VANOS job I had done resulted in both intake valves on cylinder 5 to kiss the piston and bend enough for them not to close properly. Ended up needing the seats recut as the bent valve had damaged those. Also had new guides and a set of intake valves.

Car now starts on the button every time (so far), so its probably safe to say this has been sorted.

I feel like I am clutching at straws a little bit, but is it possible I still have a fuel delivery issue? -4% long term fuel trims on both banks, open loop fault on deceleration, and the car smells noticeably rich.

Are you saying the engine start hesitation problem was due to the bent valves? I wonder why the issue was not consistence and no backfire in the intake.

-4% fuel trim is small, but since the fuel trim has been stable then the mixture should already at stoichiometric at idle and coasting.
It rings the bell in my head now, about the fuel status 8: injectors should be cut off completely during engine braking/deceleration when above certain minimum rpm but yours does not, seems to me. Maybe the DME doesn't know that the clutch and the gear are engaged -- I would look at the the clutch switch and GPS, or tune software.

[jamesfoley]

I feel like I am clutching at straws a little bit, but is it possible I still have a fuel delivery issue? -4% long term fuel trims on both banks, open loop fault on deceleration, and the car smells noticeably rich.

Is it at all possible that I have an issue with the car regulating fuel pressure when the manifold is in vacuum, and the car is getting higher fuel pressure that it expects at times? So either the air rail to FPR line having an issue, the regulator itself having an issue, or an issue related to the return line from the regulator, basically something preventing the regulation of fuel so the car is getting all the pressure all the time.

The vacuum line and FPR are new so I doubt those are the issue, however I've not touched or inspected the return line. Car has had the RACP done in the past before my ownership so everything has been apart at some point, possible that when this was put back together a line has been crushed or pinched?

I'm 99.9% sure all the fuel pressure tests at idle I've had done have been fine, would just be trying to find out if there are fuel pressure issues while driving...

[jamesfoley]

Bit of an update to this. Car is back with me now after just over two months. Long story short is the VANOS job I had done resulted in both intake valves on cylinder 5 to kiss the piston and bend enough for them not to close properly. Ended up needing the seats recut as the bent valve had damaged those. Also had new guides and a set of intake valves.

Car now starts on the button every time (so far), so its probably safe to say this has been sorted.

However, looking at data logs, I still have a lot of "Fuel System Status 8" data points.

https://datazap.me/u/jamesfoley/e46-...log=0&data=1-2

At this point I feel like maybe this is normal?

Honestly, looking at the status compared to RPM, it just looks like deceleration fuel cut, though why its 8 instead of 4 I do not know. Someone has commented that when I accelerate the car smells rich, but it runs and drives fine, and passes emissions so... 🤷

[sapote]

My bad I was mixed up, thinking you said one intake valve leaking.

[jamesfoley]

How can you tell from the leaking sound through the plenum that 1 or 2 intake valves leaking? they are both in the same port.

Not sure I understand what you mean. With air pressure into the cylinder and the crank rotated to compression stroke on cylinder 5, air was leaking through the intake.

Camera down into the cylinder shows both intake valve marks on the piston, so 1 or 2 valves are bent. Not terribly bent as the cylinder still held some pressure, but you could rotate past compression stroke by hand while filled with air, so it’s losing enough to be a problem.

Likely not the cause of my hard start as VANOS was still wrong, but I don’t want to risk dropping a valve and nuking the engine so just biting the bullet and having everything fixed.

[sapote]

1. "Both valves left an impression on the piston, but unsure if both are bent. I'd imagine if the piston kissed them both then they are equally unhappy, at least one of them is leaking air that you can hear through the plenum."
How can you tell from the leaking sound through the plenum that 1 or 2 intake valves leaking? they are both in the same port.
2. "VANOS was also found to be timed wrong again it seems, so the assumption is it was caused by timing at some point. Odd that its just a single cylinder though."
They could hit the piston hard and bent during manually turning the crank using a breaker bar, not during engine running.

With intake valve leaking, it should cause backfire in the intake, usually.