Vanos Rebuild Start Hesitation

[sapote]

Cold start log as requested with secondary air pump status: https://datazap.me/u/jamesfoley/e46-...-9-10-11-12-13

For what it's worth, its consistently starting fine from cold now ever since I swapped the MAF. Only seems to be the warmer starts that it struggles with now. The log above it started instantly with no issues whatsoever after sitting all night.

This shows pre cat bank1 sensor1 didn't drop below 0.1v during the SAP running, while bank2 sensor1 was well below 0.1v and it looks much better than bank1 sensor. So I think it's worth to replace B1 sensor1 and hope it will solve the fuel status 8 issue. Do you have stock DME software or aftermarket tuned version?

One odd thing: I never seen the secondary air status starts at 4 then drops to 1 to run the air pump. It normally starts at 1 in cold ambient and then switches to 4 after pump turned off.

[jamesfoley]

With the new MAF, do a log for cold start idle with adding Secondary air status pid (to see when SAP turn on and off) and all the o2 sensors, coolant temp, fuel status. I suspect the pre cat sensors are bad leading to fuel system status 8.
So the log should show pre cat sensors dip down below 0.1 during SAP running (too much oxygen) and swing to 0.8 when SAP turned off.

The DME voltage looks great.

Cold start log as requested with secondary air pump status: https://datazap.me/u/jamesfoley/e46-...-9-10-11-12-13

For what it's worth, its consistently starting fine from cold now ever since I swapped the MAF. Only seems to be the warmer starts that it struggles with now. The log above it started instantly with no issues whatsoever after sitting all night.

[sapote]

With the new MAF, do a log for cold start idle with adding Secondary air status pid (to see when SAP turn on and off) and all the o2 sensors, coolant temp, fuel status. I suspect the pre cat sensors are bad leading to fuel system status 8.
So the log should show pre cat sensors dip down below 0.1 during SAP running (too much oxygen) and swing to 0.8 when SAP turned off.

The DME voltage looks great.

[jamesfoley]

sapote Voltage looks rock solid here https://datazap.me/u/jamesfoley/e46-...=0&data=1-6-13

Tried to be reasonably smooth with the throttle but its still pretty jumpy

[jamesfoley]

Bit of a side question, but does anyone know the legitimacy of shadow codes within BMW Scanner?

The DME always has two "Internal fault" shadow codes that do not clear, 63 [099] and 59 [089], and I also get shadow codes for "Ignition Coil, cyl. 4" 32 [050] (multiple of the same code) which do clear, but always come back.

[jamesfoley]

Log a drive at fwy speed coasting with smooth throttle. The absolute throttle position pid jumped to very high then dropped to zero -- data look so strange.

Yea I honestly don't know if I trust the absolute throttle position in that log. There were times I had my foot on the throttle and it was coming back as 0 on the gauge. If I really had no value coming out of the pedal then the car wouldn't be accelerating and I would 100% have a code, but it drives fine so 🤷

I'll pull some PIDs and get some more logs of throttle position. Is battery voltage just "Input voltage read by the scan tool" in the PID list?

[sapote]

Log a drive at fwy speed coasting with smooth throttle. The absolute throttle position pid jumped to very high then dropped to zero -- data look so strange.

[sapote]

Battery is new as of 3 months ago and has no issues cranking, so I figured it would be fine. Ironically I changed the battery thinking it was the issue in the first place

I can add voltage to the log but with all these PIDs I'm pulling its pretty slow at refreshing so not sure how accurate the data is. What am I looking for exactly with battery voltage, dips while driving?

Everything is depending on DME voltage, i.e. injection amount, fuel pump rate. We want to know how stable is the DME voltage; a new batt with bad wire connection can cause jumpy DME voltage.

Remove the not needed pid: gps car speed, intake temp, coolant temp, MAF, as we already know they are good.

[jamesfoley]

Add voltage to the log; measure the battery voltage with voltmeter and compare.

Battery is new as of 3 months ago and has no issues cranking, so I figured it would be fine. Ironically I changed the battery thinking it was the issue in the first place

I can add voltage to the log but with all these PIDs I'm pulling its pretty slow at refreshing so not sure how accurate the data is. What am I looking for exactly with battery voltage, dips while driving?

[sapote]

Add voltage to the log; measure the battery voltage with voltmeter and compare.

[jamesfoley]

Here is a motorway drive with a fresh tank of Shell VPower

https://datazap.me/u/jamesfoley/e46-m3-motorway-drive?log=0&data=4-5&solo=2

I've included throttle position but not sure if that really helps at all. Still seeing 8's in the fuel system status and I can't see a pattern against the throttle position really.

[jamesfoley]

The new MAF improves the mixture with LTFT now in the -3 instead of -7, and the pre cat o2 sensors are responding much better. Most cars should have positive LTFT as old cars trend to lean condition and not rich, but yours is the exception. There is also the fuel system status 8 during driving, happened almost every deceleration. Based on this, I would check the throttle pedal sensors.

Have you check injectors for leaking and fuel pressure?

You mean the throttle position sensors? I know there are two on the throttle body and then the pedal right, can they be logged individually?

Would these go bad without throwing a code though, I think that's what is confusing me about everything, I have zero fault codes and its super frustrating.

Not checked injectors or fuel pressure, mainly because these are a little beyond me. Car is booked in for a new fuel regulator next week so I can get the pressure checked at the same time.

[sapote]

New genuine BMW MAF installed and DME adaptations reset, gave me the following logs:

https://datazap.me/u/jamesfoley/e46-...log=0&data=2-5
https://datazap.me/u/jamesfoley/e46-...log=0&data=2-5
.

The new MAF improves the mixture with LTFT now in the -3 instead of -7, and the pre cat o2 sensors are responding much better. Most cars should have positive LTFT as old cars trend to lean condition and not rich, but yours is the exception. There is also the fuel system status 8 during driving, happened almost every deceleration. Based on this, I would check the throttle pedal sensors.

Have you check injectors for leaking and fuel pressure?

[jamesfoley]

Interesting lean code in this case, as MAF=5g/s resulted rich with negative fuel trim and it should not suddenly change to lean, even if fuel trims were reset. Will be interested to see what a new MAF will do.

New genuine BMW MAF installed and DME adaptations reset, gave me the following logs:

https://datazap.me/u/jamesfoley/e46-...log=0&data=2-5
https://datazap.me/u/jamesfoley/e46-...log=0&data=2-5

Unfortunately no change to the starting hesitation. With the car fully up to temp and idling, taking the key out and trying to start it a minute or two later results in it struggling to catch. It honestly sounds fuel related as if for some reason in that initial crank it doesn't quite have the fuel to start so it splutters, but the only things I've not looked into are the fuel pressure regulator and the injectors themselves.

Not 100% sure how I'd be losing _all_ fuel pressure as soon as I took the key out unless the regulator is totally shagged. If the regulator was shagged it doesn't explain how I can leave it overnight and start it without issues the next morning.

Long term fuel trims are creeping into the negatives again, and the town driving log is still full of fuel system status 8 reports, so I guess something is still wrong.

The only other small thing I've noticed is that sometimes if I'm moving forward slowly and I put the clutch in and lift off the accelerator, the RPM will drop and the car almost stalls, but it picks itself back up and recovers.

[sapote]

Jumped in the car this morning and it threw a P0174 code, lean on bank 2.

Did some graphing of the MAF, RPM, and both banks Short fuel trim and noticed the RPM fluctuates slightly, with the short trims going positive and negative constantly while idle, and the MAF sits at 5 g/s or above. I'm assuming it's upset about the fuel mixture and is constantly trying to compensate with a wrong MAF reading?.

Interesting lean code in this case, as MAF=5g/s resulted rich with negative fuel trim and it should not suddenly change to lean, even if fuel trims were reset. Will be interested to see what a new MAF will do.