Mystery abnormal throttle response

its 180 for diagnostic fee..

Hey guys,
Let me know Ive got a simialar prob,,car sat for 10 months,,,Long story short would idle,,found cracks in the all the tubes and replaced the ccv and tubes,,,,Idles perfect now but in 5th(auto) on the hwy idle bounces up and down, and can feel the car not right,,,Driving me nuts,,,only code was po444 on the cheap machines,,,but looking around on here,Hell it might be the Disa valve,,,a vacuum leak(again),,o2 sensor,cat,, dmu,, now read may be a tranny prob...But if i put my cruise on it kinda holds steady,,, I may take to dealer just to see what codes they pull up,,,but gotta save up the 135 hook up price,,,, tired of pulling my hair out,,,and just cant keep throwing parts at it,,,

Originally Posted by SweetBMW

Might be your accelerator pedal module-... BMW SI bulletin says that customers have complained about this exactly problem with a delay in throttle response. This was resolved with a new module at the cost of 150USD

Yup. Id say this could be it.

well it wouldnt be the accelerator module rather but the poteniometer that measures the ressistance and sends a signal to the throttlebody's

Originally Posted by AMG Killer

well it wouldnt be the accelerator module rather but the poteniometer that measures the ressistance and sends a signal to the throttlebody's

Hey now, careful with those big words, haha. Bently's says there are two pots in the module and Ill be checking them both over Thanksgiving. Do you know what the range and tolerance for the pots are? Bently's doesn't have that info. Also is there a good resource for more advanced technical info like i/o voltages and resistances of different sensors on this car?

While this seems like this is a good place to start, I am still not very convinced this is the problem. it doesn't occur when the car is not under load, i.e. the car is in neutral or the clutch is pushed in. I would think if it were something in the accelerator pedal, the problem would occur 100% of the time regardless of weather the clutch was in or not. Are there other potentiometer type sensors in the gear box somewhere?

I also want to clarify that this is not the Stick-slip effect explained here:

http://www.meeknet.co.uk/E38/E38_Sti...ttle_Pedal.pdf

Update:

I finally got around to checking out the accelerator pedal module. Apparently there are two potentiometers behind the pedal that detect pedal position. I took a multimeter and measured the resistances between the six different pins on the module. I was able to find what pins go to which pot and determined that the two pots are not connected. This is confirmed by the wiring diagram in Bentleys.

The thing that has me totally stumped is that the resistances didn't change when the pedal was pressed. This is completely perplexing to me, since if the resistances don't change when the pedal is moved, the computer should not be getting any signal at all, yet the car revs fine (except for the original issue). Any input on the would be helpful. Thanks.

Here are the measured resistances:
Pot 1: pin 1-4 = 57 ohms, pin 4-5 = 427 ohms, pin 1-5 = 477 ohms
Pot 2: pin 2-6 = 57 ohms, pin 3-6 = 427 ohms, pin 2-3 = 477 ohms

Also, I drove the car 8 hours (at the speed limit) in heavy rain a week ago. My destination was 3000 ft lower in elevation than home. After this trip, the response issue was much better, and I had more power across. The problem is slowly coming back as I am driving around town.

Again these did not change when the pedal was pressed

Hmm, your car does seem to have the symptoms associated with a bad accelerator pedal. The DME will slow responses to sudden changes in input when it detects a fault.

Btw, there are two different types of drive-by-wire systems on E46s. One style uses pedal linkage to actuate two potentiometers, the other style is an enclosed pedal. I believe you have the latter, which uses hall sensors, so you need to apply +5V (as the DME does, but you could probably use a little more/less) across pins 5 and 1 and measure voltage at 4, or across 3 and 2 and measure at 6. One output should measure exactly half of the other.

PWG modules (aka. accelerator pedals) rarely go bad. the issue people are referring to is the sticky/notchy "stick-slip effect" pedal feel. It is purely mechanical and is related to the lubricant used on the pedal that causes the mechanism inside to bind when it gets hot (parked car in summer or heater on in winter) OP, you would physically feel the pedal sticking if it were to blame. Also, the EML would go to failsafe if there were any issues with the potentiometers in the pedal so I doubt that's it.

Since the condition changes with altitude, I would look to an intake leak like the DISA valve. It seems like they tend to go bad in the winter.

Originally Posted by iansanderson

PWG modules (aka. accelerator pedals) rarely go bad. the issue people are referring to is the sticky/notchy "stick-slip effect" pedal feel. It is purely mechanical and is related to the lubricant used on the pedal that causes the mechanism inside to bind when it gets hot (parked car in summer or heater on in winter) OP, you would physically feel the pedal sticking if it were to blame. Also, the EML would go to failsafe if there were any issues with the potentiometers in the pedal so I doubt that's it.

Since the condition changes with altitude, I would look to an intake leak like the DISA valve. It seems like they tend to go bad in the winter.

I completely agree. I have read up on the stick slip effect and I know it was not that. I had a vacuum leak test done, and it passed, so I figured it could be the pedal, disa, ICV or TB. I pick the cheapest to rule out and am working my way up to the most expensive.

Also, I found a bunch of info on the Hall sensors. take a look here: http://www.bmwmotorsports.org/BMW_docs/m54x5.pdf
Is there a place that has a lot of technical info on the E46, like the voltage in and out for other sensors/actuators?

Originally Posted by cyberkaa

Btw, there are two different types of drive-by-wire systems on E46s. One style uses pedal linkage to actuate two potentiometers, the other style is an enclosed pedal. I believe you have the latter, which uses hall sensors, so you need to apply +5V (as the DME does, but you could probably use a little more/less) across pins 5 and 1 and measure voltage at 4, or across 3 and 2 and measure at 6. One output should measure exactly half of the other.

This was spot on! thanks for the info. Here is what I did. USB is 5V so you can take a USB charger for a phone (iphone / ipod / etc) and plug an old printer cable into it. Then cut the other end of the printer cable off and use the red and black wires. Instant 5V power supply. (Double check the 5V with a multi meter before connecting it to the pedal).

hall sensor 1: Pin 1 = negative, Pin 5 = positive, measure at pin 4
hall sensor 2: Pin 2 = negative, Pin 3 = positive, measure at pin 6
measure each sensor separately, red lead of your multimeter on 4 or 6, black lead on 1 or 2 respectively. Make sure your volt meter is set to voltage. Now depress the accelerator pedal and you will see the voltage change.

Results: I got .72V - 4V on sensor 1 and .37V - 2.0V on sensor 2. From what I have read, sensor 1 should be .5V - 4.5V and sensor 2 should be .5V - 2V. Since the maximum is 4V instead of 4.5V I am only getting 88% of max throttle, I believe this warrants a replacement. If you disagree let me know.

I know this thread is getting a bit old, but I hope you found a resolution. I recently picked up a 2002 325xi that behaves exactly as you described in your original post.

Did you get it resolved?

Unfortunately, I have not resolved this and have decided to give up for now. I know it is not the pedal, the maf, the tb, or the icv. Since the problem is predictable and not constant, its safe to assume its not a mechanical failure. I am 90% sure it is a software issue or a speed sensor issue. My dealer charges $120 for a software update so I decided to let it ride and see if it gets worse. If you really want it solved I would take your car to the dealer and make sure the software is up to date.

Does anyone know the latest version numbers for the various modules software?

Here's a crazy idea: with the engine off, press the pedal to the floor with your hand as hard as you can, then release. Is it springing back immediatly, or sticking?

I have the same problem, almost got into an car wreck because of the anoying 1 to 2 second throttle response delay. It gets worse when I use heater and set it to blow down on feet, this would explain that heat is effecting the pedal and module.

Hey guys, just wanted to make an entry to this thread for future reference.

Cyberkaa mentioned that there were two types of pedal control modules (PWG): one with a potentiometer and one with a hall-effect rotary angle sensor. I was able to confirm this but there's almost no information on which part number corresponds to which type of sensor.

After some thinking I realized there's a fundamental difference between the two sensor types that make them easy to identify:
- The potentiometer is a physical connection (i.e., theres a contact that slides along a resistor to get a signal). It will yield a varying resistance value between the positive lead and the signal lead whenever the pedal is depressed -regardless of a power source being supplied.
- The hall-effect sensor is a magnetic field induced signal (i.e., theres no physical connection between the signal wire and the power source). Therefore it will yield an unchanging resistance value when the pedal is depressed. A 5v power source MUST be applied to get any reading from the signal leads if you have the hall-effect rotary angle sensor style throttle pedal.

Fr3nch had a fantastic idea to use an old 5v DC phone charger as a power source for a bench test, do that if you need to take it out of the car.

notes:
Pin assignments:
Sensor 1
- Positive lead = pin 5
- Signal lead = pin 4
- Negative lead = pin 1

Sensor 2
- Positive lead = pin 3
- Signal lead = pin 6
- Negative lead = pin 2

Accelerator Pedal Module (with hall effect style rotary angle sensor):
PN: 35426786282

I had this issue you stated: "Some other possibly related things (that I am not even sure are problems): when the engine is revved briefly, it dips below idle, then goes above idle, then settles at idle. If the engine is revved high is does not do this."

as well as loss in power around 2800-3000 rpm, it resulted in a jerking feel. I fixed it by updating the DME software. My car used to stall all the time in traffic due to the issue above, but I haven't stalled since.

I have been battling this same issue to a T, with the addition of acceleration surge around 2,500-3k rpm.

I have replaced the MAF, tested and re-sealed the DISA, with a minor improvement

Things which affect the symptoms include very humid/rainy, and AC use.