Vanos Rebuild Start Hesitation

[jamesfoley]

Just want to get some clarification on something.

MSS54 documentation says that the throttle body TPS should be 0.5v closed and 4.5v open, with the TPS on the actuator flipped at 4.5v closed and 0.5v open.

Pulling TPS values from DIS I have 0.39v closed and 3.94v open on the throttle body, then 4.35v closed and 0.57v open on the actuator.

Actual throttle positions are going 0-100% so I'm guessing it adapts to the open and closed position values.

Is it possible that either of those are worth replacing?

[jamesfoley]

Mine also has status 8 sometimes; never see 8 on M52 or M54 engines.
It has stock Dme firmware

Was just wondering if its an early software version thing really. if yours was also as old as mine it might be, though if yours is more recent then its doubtful.

If fuel return hose blocked, you would run out of fuel with half capacity show on gauge due to suction pump not working to transfer left to right tank

Fair point, all return is done through the same line that the regulator bleeds through.

[sapote]

Mine also has status 8 sometimes; never see 8 on M52 or M54 engines.
It has stock Dme firmware

If fuel return hose blocked, you would run out of fuel with half capacity show on gauge due to suction pump not working to transfer left to right tank

[jamesfoley]

Postcat sensors don't control DME, but they indicate the rich condition of mixture (unless they are old and bad that don't function properly). IOW, they smell too much fuel and switching as the precat instead of staying at high level most of the time.

ICV is ok.

bad purge valve should pop the error code, so I think it's fine

fuel return hose can't be blocked.

measure the fuel pressure anywhere between regulator output and fuel rail.

here is the log:


https://datazap.me/u/sapote/e46-m3?log=0&data=10

I mean, looking at that log you do have the same open loop fault readings that make me think its normal for the MSS54 to do that for some reason? Out of curiosity whats the software version on your DME?

The fuel return idea came about because a previous owner has done the RACP work, which means the fuel tank has been out before. More so wondering if the fuel return was pinched or damaged rather than physically blocked.

[sapote]

Postcat sensors don't control DME, but they indicate the rich condition of mixture (unless they are old and bad that don't function properly). IOW, they smell too much fuel and switching as the precat instead of staying at high level most of the time.

ICV is ok.

bad purge valve should pop the error code, so I think it's fine

fuel return hose can't be blocked.

measure the fuel pressure anywhere between regulator output and fuel rail.

here is the log:

https://datazap.me/u/sapote/e46-m3?log=0&data=10

[jamesfoley]

As about the fuel pressure, just verify this with a P gauge at different rpm. Also check injectors condition.

Is the pressure from the valve on the regulator what I should be seeing at the rail, or just from the pump?

Sort of tempted to get the Radium rail installed just for the pressure gauge on the end of the rail. Would also be kind of nice to get a digital fuel pressure gauge just because it'd be somewhat useful.

I looked up my M3 log, it did have a few status 8 during deceleration, but the total fuel trim is around 3.2 at hot idle; yours shows rich with negative fuel trim and switching postcat sensors.

Any chance you could post the log for me to take a look at?

Post-cat sensors do nothing fuel map wise though right, they just monitor the efficiency of the cat itself, so worst case is it'd just fail emissions due to worn cats.

I can't think of any way the car can be accidentally too rich that I haven't already covered...

ICV not opening enough at idle so its getting less air than it thinks it is? I cleaned this already so it'd be a faulty ICV if anything.
Injectors were replaced with a known good (cleaned and flow tested) set with no change, so they shouldn't be leaking.
FPR is new so I shouldn't be enriching anything through the vacuum line.
Purge valve could be stuck open, but this would be a vacuum leak more than anything right? Certainly shouldn't be enough vapour to make it rich all the time unless my carbon canister is saturated or something...
Fuel return being blocked so injectors are seeing full pressure all the time would be a reasonable cause for the car to pull fuel all the time. It should read less pressure at idle compared to when the engine has a load right?

[sapote]

[/LIST]Along with anything in the list above being the culprit, two other thoughts are:

• DME running software that isn’t stock
• Fuel pressure isn’t being bled off by the regulator, pressure too high at idle / closed throttle. Possible issue with fuel return.

your MAF looks fine.

The post cat sensors in the log show they couldn't treat the exhaust gas properly during driving -- both followed the precat sensors; could be old tired cats or rich mixture that couldn't be treated. I think the mixture are rich is the issue.

As about the fuel pressure, just verify this with a P gauge at different rpm. Also check injectors condition.

I looked up my M3 log, it did have a few status 8 during deceleration, but the total fuel trim is around 3.2 at hot idle; yours shows rich with negative fuel trim and switching postcat sensors.

[jamesfoley]

should provide total fuel trim, ltft alone is not enough. This sounds rich mixture which is very unusual, and the little high idle also supports the theory.
You should check the MAF rate even if it's new. Low reported MAF can cause rich running.

We had proved it wasn’t MAF related, here is a warm no accessories log from a while back: https://datazap.me/u/jamesfoley/e46-...no-accessories

Worth mentioning that the car does still sputter for a second or two when it starts, but it’s very intermittent.

Also the car sometimes starts too quickly. The engine barely rotated before it catches and starts, as if it starts as soon as the key is turned. Not like this is an issue, but it’s just weird to have it instantly start up.

There are still a handful of parts I’ve not replaced:

• Intake camshaft sensor
• Exhaust camshaft sensor
• TPS under intake
• TPS next to oil filter
• Throttle pedal
• Fuel tank purge valve
• Idle air control valve (though I did clean it)

Along with anything in the list above being the culprit, two other thoughts are:

• DME running software that isn’t stock
• Fuel pressure isn’t being bled off by the regulator, pressure too high at idle / closed throttle. Possible issue with fuel return.

[sapote]

Hot idle LTFT’s sit around -5% both banks, give or take a couple of percent depending on how the car feels.

Idle rpm seems to hover between 870 to 890.

should provide total fuel trim, ltft alone is not enough. This sounds rich mixture which is very unusual, and the little high idle also supports the theory.
You should check the MAF rate even if it's new. Low reported MAF can cause rich running.

[jamesfoley]

IF Evap leaking then you sure have a code.
I don't think ICV at issue, as this should cause bad idling but you have steady idle rpm at around 850, do you?

Had you posted fuel trims at hot idle before?

Hot idle LTFT’s sit around -5% both banks, give or take a couple of percent depending on how the car feels.

Idle rpm seems to hover between 870 to 890.

[sapote]

I mean I guess it’s possible the ICV isn’t letting enough air through, or too much through for what’s being commanded? Another thought is an issue with the EVAP purge valve leaking and enriching the mixture causing it to run richer than expected?

MAF is brand new from BMW and rates were fine last time they were checked.

IF Evap leaking then you sure have a code.
I don't think ICV at issue, as this should cause bad idling but you have steady idle rpm at around 850, do you?

Had you posted fuel trims at hot idle before?

[jamesfoley]

So why status 8 only happened with closed throttle -- this is the key to solve the mystery. I don't remember if you posted the MAF rate in g/sec; just want to make sure it's not related to bad MAF.

I mean I guess it’s possible the ICV isn’t letting enough air through, or too much through for what’s being commanded? Another thought is an issue with the EVAP purge valve leaking and enriching the mixture causing it to run richer than expected?

MAF is brand new from BMW and rates were fine last time they were checked.

It would be awesome if there was a way just to see what criteria the DME used to trigger a fuel status of 8.

There is always the possibility that it’s just normal fuel cut on deceleration…

[sapote]

Little bit more research and it appears the MSS54 doesn't only use the actual throttle body for engine load below 15%, so low speed, low engine load, low throttle input, the Idle Control Valve actually provides air. So I guess the 0% throttle position is actually where the ICV is providing air and the throttle bodies stay closed?

I have had the ICV out and cleaned it to free up the flap inside, but I mean it wasn't bad to begin with, and cleaning it made no difference. Hopefully its not still causing issues, from all my logs I can't find a fuel system status 8 reading where the throttle position isn't reading 0...

So why status 8 only happened with closed throttle -- this is the key to solve the mystery. I don't remember if you posted the MAF rate in g/sec; just want to make sure it's not related to bad MAF.

[jamesfoley]

From the log I see fuel status 8 happened only once in idle.
I don't see any correlation between status 8 and ignition timing, as below pic shows 24* ignition advaced. I do see all of these status 8 happened with absolute throttle = 0. Could be an intermittent faulty throttle sensor tells the DME it's closed but it's not, hence the status 8?

After a bit of research it sounds like ignition timing should drop to 0 the same way fuel is cut on deceleration / throttle close, but I thought it should be fuel status 4, not 8 with a fault.

Faulty TPS is plausible, though again from what I’ve read they always throw a fault code of some sort. Been a good few months with not a single code being thrown.

I don’t really understand the relation between throttle position reported in my log compared to the actual throttle position, as the log shows it at 0% a lot of the time. If it was always 0% the car wouldn’t be drivable…

Edit to avoid double posting:

Little bit more research and it appears the MSS54 doesn't only use the actual throttle body for engine load below 15%, so low speed, low engine load, low throttle input, the Idle Control Valve actually provides air. So I guess the 0% throttle position is actually where the ICV is providing air and the throttle bodies stay closed?

I have had the ICV out and cleaned it to free up the flap inside, but I mean it wasn't bad to begin with, and cleaning it made no difference. Hopefully its not still causing issues, from all my logs I can't find a fuel system status 8 reading where the throttle position isn't reading 0...

[sapote]

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.

From the log I see fuel status 8 happened only once in idle.
I don't see any correlation between status 8 and ignition timing, as below pic shows 24* ignition advaced. I do see all of these status 8 happened with absolute throttle = 0. Could be an intermittent faulty throttle sensor tells the DME it's closed but it's not, hence the status 8?