Sudden rough idle

jfoj · #1 12-15-2015, 01:15 AM

MAF is not likely the issue. MAF's do not over report when they get dirty, they under report. MAF's also under report as they degrade and age.

The MAF reading is a bit high, however, I would not take the single instance of the MAF reading as a benchmark at this point. If the MAF was really over reporting, then I would expect the Fuel Trims to be fairly Negative.

You really need to change the MAF reading from lb/min to g/s. This is VERY easy. Go Settings, Units, Airflow and change from lb/min to g/s.

Forget about the MAF for now, there are plenty of other things to focus on.

A few things seem to be out of line.

Pay very careful to the Fuel System Status information.

For the report, the Fuel System Status was at 8 for both Banks.

8 = Open loop due to system failure

For the Freeze Frame, the Fuel System Status was at 4, unclear if this was due to off throttle deceleration or why it was at 4 for the Freeze Frame.

4 = Open loop due to engine load OR fuel cut due to deceleration

Input voltage read by the scan tool 12.6 V. This could be a problem, this could be an offset reading due to a cheap OBDII interface that has a poor Voltage detection circuit.

I would verify the charging Voltage on the vehicle and make sure there is not a basic charging problem or a bad engine to body ground. You may find the OBDII interface is just reading low and you may need to add a correction factor.

Fuel Trims do not look too bad with the initial snap shot of data. I do not think there is a vacuum leak problem at this time with the snap shot of data, but maybe my mind with change when I can see some Logs.

However, the Bank #1 O2 sensor Voltages look very low from the Report snap shot. This means at least Bank #1 was very Lean when the Report was generated. But again, this is just a snap shot so the data may be a bit misleading.

I really doubt this problem is due to ignition coils, but is there any chance you have had a lot of rain or run the vehicle through a car wash?

Possible bad fuel?

Fuel pump failing and going soft is also a very common problem on BMW's. E46 have a big problem with this, I do not have the data for the E53, they may also run a Piersburg pump which may be slightly more robust than the Siemens/VDO pumps. If the vehicle has 1/4 tank this is a common level where driveability problems start of the fuel pump is soft. You could try to use the Hidden OBC Menu and verify the fuel level in both sides of the fuel tank. Below 1/2 tank the drivers/left side should typically be empty and never have more fuel than the passenger/right side. In the short term if the fuel tank is at 1/4 level, add about 5 more gallons and see how the vehicle runs.

If you could post up a few Logs this would be helpful and allow me to see more than just a snap shot.

OBDFusion will Logs while the App is connected to the vehicle.

This info may be a bit dated, some of the Menus or Tabs may be different, however, this is what you need to do for setting up Logging.

First change the MAF reading from Pounds/Min to Grams/Sec, stupid EASY.

Settings, Units, Airflow, choose g/s.

Temp sometimes can be more useful in C vs F, but no so critical.

Settings, Log Setup then set the following:

Logging Enabled - checked

Logging Trigger - choose Trigger at a fixed sample time

Sample Time - choose 1000 msec

Log GPS Items - suggest you un-select it as to not advertise where you live

Select Items to Log - This varies a bit for each car. But here is a list I like to see:

Fuel - do not check any of these 3 items

SAE PID's:

Fuel system 1 status
Fuel system 2 status
Calculated load value
Engine coolant temperature
Short term fuel % trim - Bank 1
Long term fuel % trim - Bank 1
Short term fuel % trim - Bank 2
Long term fuel % trim - Bank 2
Engine RPM
Vehicle speed
Ignition timing advance for #1 cylinder
Intake air temperature
Mass air flow rate
O2 Voltage (Bank 1, Sensor 1) - not all cars have this
O2 Voltage (Bank 1, Sensor 2) - not all cars have this
O2 Voltage (Bank 2, Sensor 1)
O2 Voltage (Bank 2, Sensor 2)
O2 sensor Voltage wide range (Bank 1, Sensor 1) - not all cars have this
O2 sensor Voltage wide range (Bank 2, Sensor 1) - not all cars have this
Input Voltage read by the scan tool

Before you clear codes, get the Freeze Frame data and email or save the screen shot if this is an option. Freeze Frame data saves about 20+ questions as to what is going on.

Then make the following Logs:

4 minutes cold start letting the engine idle, do not drive or touch the throttle. Make sure the App is connected to the vehicle before you start the engine. Usually you need to turn the ignition on but do not start the engine, the Connect the App. Once the App is connected and sees the OBDII data stream start the engine.

4 minutes warm idle in Park or Neutral.

3-4 minutes steady highway cruise on as flat a surface as you can find. Cruise control is nice to use if possible. 45-65 range.

Logs will be found under Logs, Files and will be listed by Date and Time.

I need the .CSV files to be Shared.

You can set up a DropBox Free account and OBDFusion can seamlessly upload the chosen Log files to DropBox. You can then log into your DropBox account and choose the file, select Share, then copy and paste the Share URL back into the thread here and I can then access the Logs and look a the data in more detail.

NOTE ON SETTING UP DROPBOX.

You will need to set up a DropBox Free account using your computer. Use a Login Name, typically your email address, the choose a Password. You will add these into the OBDFusion App under Settings, DropBox.

When setting up your DropBox account on your computer. DO NOT DOWNLOAD AND INSTALL THE DROPBOX SOFTWARE. IT IS NOT NEEDED AND IT WILL CAUSE SOME PROBLEMS TRYING TO SYNC FILES FROM YOUR COMPUTER TO DROPBOX AND QUICKLY FILL UP YOUR DROPBOX FREE ACCOUNT. IT CAN BE MANAGED, BUT JUST DO NOT INSTALL THE DROPBOX SOFTWARE, IT IS NOT NEEDED.

When setting up DropBox, after you enter your Password and DropBox prompts you to download their software, just hit the Back browser arrow and you will then be in your newly created account.

upallnight · #2 12-15-2015, 08:39 AM

Quote:

Originally Posted by jfoj

MAF is not likely the issue. MAF's do not over report when they get dirty, they under report. MAF's also under report as they degrade and age.

The MAF reading is a bit high, however, I would not take the single instance of the MAF reading as a benchmark at this point. If the MAF was really over reporting, then I would expect the Fuel Trims to be fairly Negative.

You really need to change the MAF reading from lb/min to g/s. This is VERY easy. Go Settings, Units, Airflow and change from lb/min to g/s.

Forget about the MAF for now, there are plenty of other things to focus on.

A few things seem to be out of line.

Pay very careful to the Fuel System Status information.

For the report, the Fuel System Status was at 8 for both Banks.

8 = Open loop due to system failure

For the Freeze Frame, the Fuel System Status was at 4, unclear if this was due to off throttle deceleration or why it was at 4 for the Freeze Frame.

4 = Open loop due to engine load OR fuel cut due to deceleration

Input voltage read by the scan tool 12.6 V. This could be a problem, this could be an offset reading due to a cheap OBDII interface that has a poor Voltage detection circuit.

I would verify the charging Voltage on the vehicle and make sure there is not a basic charging problem or a bad engine to body ground. You may find the OBDII interface is just reading low and you may need to add a correction factor.

Fuel Trims do not look too bad with the initial snap shot of data. I do not think there is a vacuum leak problem at this time with the snap shot of data, but maybe my mind with change when I can see some Logs.

However, the Bank #1 O2 sensor Voltages look very low from the Report snap shot. This means at least Bank #1 was very Lean when the Report was generated. But again, this is just a snap shot so the data may be a bit misleading.

I really doubt this problem is due to ignition coils, but is there any chance you have had a lot of rain or run the vehicle through a car wash?

Possible bad fuel?

Fuel pump failing and going soft is also a very common problem on BMW's. E46 have a big problem with this, I do not have the data for the E53, they may also run a Piersburg pump which may be slightly more robust than the Siemens/VDO pumps. If the vehicle has 1/4 tank this is a common level where driveability problems start of the fuel pump is soft. You could try to use the Hidden OBC Menu and verify the fuel level in both sides of the fuel tank. Below 1/2 tank the drivers/left side should typically be empty and never have more fuel than the passenger/right side. In the short term if the fuel tank is at 1/4 level, add about 5 more gallons and see how the vehicle runs.

If you could post up a few Logs this would be helpful and allow me to see more than just a snap shot.

OBDFusion will Logs while the App is connected to the vehicle.

This info may be a bit dated, some of the Menus or Tabs may be different, however, this is what you need to do for setting up Logging.

First change the MAF reading from Pounds/Min to Grams/Sec, stupid EASY.

Settings, Units, Airflow, choose g/s.

Temp sometimes can be more useful in C vs F, but no so critical.

Settings, Log Setup then set the following:

Logging Enabled - checked

Logging Trigger - choose Trigger at a fixed sample time

Sample Time - choose 1000 msec

Log GPS Items - suggest you un-select it as to not advertise where you live

Select Items to Log - This varies a bit for each car. But here is a list I like to see:

Fuel - do not check any of these 3 items

SAE PID's:

Fuel system 1 status
Fuel system 2 status
Calculated load value
Engine coolant temperature
Short term fuel % trim - Bank 1
Long term fuel % trim - Bank 1
Short term fuel % trim - Bank 2
Long term fuel % trim - Bank 2
Engine RPM
Vehicle speed
Ignition timing advance for #1 cylinder
Intake air temperature
Mass air flow rate
O2 Voltage (Bank 1, Sensor 1) - not all cars have this
O2 Voltage (Bank 1, Sensor 2) - not all cars have this
O2 Voltage (Bank 2, Sensor 1)
O2 Voltage (Bank 2, Sensor 2)
O2 sensor Voltage wide range (Bank 1, Sensor 1) - not all cars have this
O2 sensor Voltage wide range (Bank 2, Sensor 1) - not all cars have this
Input Voltage read by the scan tool

Before you clear codes, get the Freeze Frame data and email or save the screen shot if this is an option. Freeze Frame data saves about 20+ questions as to what is going on.

Then make the following Logs:

4 minutes cold start letting the engine idle, do not drive or touch the throttle. Make sure the App is connected to the vehicle before you start the engine. Usually you need to turn the ignition on but do not start the engine, the Connect the App. Once the App is connected and sees the OBDII data stream start the engine.

4 minutes warm idle in Park or Neutral.

3-4 minutes steady highway cruise on as flat a surface as you can find. Cruise control is nice to use if possible. 45-65 range.

Logs will be found under Logs, Files and will be listed by Date and Time.

I need the .CSV files to be Shared.

You can set up a DropBox Free account and OBDFusion can seamlessly upload the chosen Log files to DropBox. You can then log into your DropBox account and choose the file, select Share, then copy and paste the Share URL back into the thread here and I can then access the Logs and look a the data in more detail.

NOTE ON SETTING UP DROPBOX.

You will need to set up a DropBox Free account using your computer. Use a Login Name, typically your email address, the choose a Password. You will add these into the OBDFusion App under Settings, DropBox.

When setting up your DropBox account on your computer. DO NOT DOWNLOAD AND INSTALL THE DROPBOX SOFTWARE. IT IS NOT NEEDED AND IT WILL CAUSE SOME PROBLEMS TRYING TO SYNC FILES FROM YOUR COMPUTER TO DROPBOX AND QUICKLY FILL UP YOUR DROPBOX FREE ACCOUNT. IT CAN BE MANAGED, BUT JUST DO NOT INSTALL THE DROPBOX SOFTWARE, IT IS NOT NEEDED.

When setting up DropBox, after you enter your Password and DropBox prompts you to download their software, just hit the Back browser arrow and you will then be in your newly created account.

If the system is in "Open Loop" as you suggested, then the 02 sensors are not controlling the fuel mixture. Fuel mixture is only controlled by the 02 sensors when the system goes into "Close Loop".

jfoj · #3 12-15-2015, 09:22 AM

Quote:

Originally Posted by upallnight

If the system is in "Open Loop" as you suggested, then the 02 sensors are not controlling the fuel mixture. Fuel mixture is only controlled by the 02 sensors when the system goes into "Close Loop".

I am clearly aware of the system being in "Open Loop" but what is important is there are 5 different states of Open or Closed Loop.

Fuel System Status 8 is not a good think, typical engines that are running correctly only have Fuel System Status 1 & 2 and occasionally 4 during deceleration with fuel cut off.

Again, this is why Logs would be helpful to compare Cold Start against Warm Idle and Steady Cruise.

Often I see Fuel System Status 8 during cold start when there is an extremely Lean condition where the fuel control system is not able to see the O2 sensor respond to changed int he fuel control.

Logs will give MUCH more insight to what may be going on here.

In the back of my mind I am thinking fuel starvation duel to a soft fuel pump, but I need more info to include what the current vehicle fuel level is.