"throttle potentiometer" = "throttle valve" on M50 525?

[Dave M]

There have been a few posts including this one started by KenB (http://www.bimmer.info/forum/showthread.php?t=26887&highlight=1216) regarding running problems due to a number of potential causes. As my 525 has been hiccuping (mainly while warming up, but recently under all conditions), I have done some searching and reading in order to help narrow down the problem source.

Background:

90/10 M50 525, 520,000+km. Recently rebuilt engine. Running well until mid summer when it started to 'fumble' at idle and 'hiccup' on acceleration. The symptoms are much like those inBob's (http://www.bimmer.info/forum/showthread.php?t=26487&highlight=DME+relay), except I pulled a 1216 fault code indicating "throttle potentiometer". The engine will suddenly cut-out for a half second, recover, cut-out, recover etc. This will occur for a minute or so, then run normally. When it hiccups, the CEL and (ABS?) light illuminate for a very brief period. Battery voltage tested at 12.75, so it seems fine.

FWIW, Bob seems to have fixed his issues with a new DME relay and replacement ICV. KenB has had some luck with a new battery, but the issue may have returned, hmmmmm.

To my question:

In the first post link, someone states that the throttle potentiometer is located at near the gas pedal. Just to clarifiy, is the "throttle valve" mentioned in Bentleys (see below) analogous to the "throttle potentiometer" as per the 1216 code? If so, the position at the foot well might only apply to traction control equiped vehicles. Anyone?

Page 130-2 of Bentley Manual

http://img.photobucket.com/albums/v11/dave_macisaac/Throttle_Valve_Bentleys.jpg

Tomorrow I check the engine coolant temp sensor, the intake air temp sensor and the throttle position sensor. I'll be back with an update, of course.......

Dave M

[Blitzkrieg Bob]

since you did an engine swap, did you check all the grounding points?

If you painted the engine bay, some may painted over or they could be loose.

[Dave M]

since you did an engine swap, did you check all the grounding points?

If you painted the engine bay, some may painted over or they could be loose.


Good point. I did just check the main ground at the front pass. side engine mount. I did some painting, so I will stick my head in there tomorrow and check some other spots.

About the throttle question, I didn't read ahead. F'in tard

http://img.photobucket.com/albums/v11/dave_macisaac/Throttle_Potentiometer_Bentleys.jpg

OOOps

[Dave M]

Had to go and test the throttle valve sensor. I must pre-empt this by Admitting I am super electrically stupid and stunned. Results below.

http://img.photobucket.com/albums/v11/dave_macisaac/Throttle_Potentiometer_Bentleys_Cha.jpg

The resistance values were fine, but the first voltage test did not work when performed as described in the chart (hence the big X ;) ). I tried all three harness connector 'tabs' (trying to locate the ground, which I first assumed matched #1 on the sensor terminal), while also connected to #1 on the terminal as per instructions. No voltage. Then I thought, why not try the center tab on the harness (I'm now guessing the ground on the harness) while grounding to a strut mount stud rather than sensor terminal 1. Bingo.......5 VDC.

So, am I doing something wrong, is this normal, or is it time for a new sensor?

Thanks for reading,

Dave m

[632 Regal]

sounds like a break in the harness ground wire to me. Im also electronically challanged but it kida points to that. If you knew for sure which is supposed to be the ground you could bend the wires until it suddenly showed voltage?

[bill g]

If you are talking about testing the throttle position sensor as per Bentleys page 130.8 - there is something wrong with Bentleys procedure. My wifes 1992 325i M50 has same sensor which is in good working order as far as I know - I measured voltages between harness connector terminals and body earth -
pin no 3 (top) 5v
pin no.2 5v
pin no. 1 6.5mV (this pin is earthed)

Also, voltage between terminals 1 and 3 5V.

Hope this helps.

Bill G

[Dave M]

If you are talking about testing the throttle position sensor as per Bentleys page 130.8 - there is something wrong with Bentleys procedure. My wifes 1992 325i M50 has same sensor which is in good working order as far as I know - I measured voltages between harness connector terminals and body earth -
pin no 3 (top) 5v
pin no.2 5v
pin no. 1 6.5mV (this pin is earthed)

Also, voltage between terminals 1 and 3 5V.

Hope this helps.

Bill G

Thanks guys. Jeff, I wish it was as simple as a bum sensor, my neck is getting sore ;) Not ready to drive my truck yet.

Bill, yes, its the procedure on 138-8. Thanks for your data, maybe there is something here. First, when you say harness connector terminals, I assume you refer to the removable harness, not the stationary sensor.

So by your description, harness pin #1 is the 'ground'. Correct?

Now, when I tested all three harness pins to the strut (ground), I recorded the following (Note, my VDC was set at 20V, so I may be limited):

pin no 3 (top) negligible
pin no.2 5v
pin no. 1 negligible (this pin is earthed)

Does this mean anything to anyone?

I'll be testing the air and coolant temp sensors this evening.

P.S. it really feels as though the fuel is quickly shut off for a moment via some sensor. The 'hiccup' can get pretty violent accelerating from a stop, and its still worse in colder morning temps when the car warms up (like this morning %&$#%^$$)

Dave M

[ryan roopnarine]

dave, my car will throw ICV, MAF, and TPS codes any time one of the three is being defective, they are all "integral" to each other working properly. i have a nominally working ICV and MAF (i had to use my spare TPS on my car) and a TPS that seems to work acceptably so long as you don'tuse the kickdown switch. is this the problem that has been going on since you put the motor back in the car, or before that? at any rate, i can send the stuff up there (if i can find it) and you can borrow and check if you like. nonvanos m50, right?

[Dave M]

dave, my car will throw ICV, MAF, and TPS codes any time one of the three is being defective, they are all "integral" to each other working properly. i have a nominally working ICV and MAF (i had to use my spare TPS on my car) and a TPS that seems to work acceptably so long as you don'tuse the kickdown switch. is this the problem that has been going on since you put the motor back in the car, or before that? at any rate, i can send the stuff up there (if i can find it) and you can borrow and check if you like. nonvanos m50, right?

Ryan,

Yeah, after reading the bentleys, it seems that its anybody guess as to which bit is screwing with the fuel and or air. I'm still curious as to why my throttle valve sensor (TPS?) readings are inconsistent with Bentley and Bills readings.

Are you saying you have a spare, working ICV and TPS? If so, I may ask to borrow them (I have tested my MAF and its working properly). I'm in no huge hurry, but would like to sort it out before i put it to bed for the winter.

I'll do some more investigating and get back to you. Thanks for the offer.

Oh, and yes, its a non-vanos (should it matter that its a manual tranny?)


Dave M

[neil_004]

I had a similar problem with my car. Same TPS code. No other codes stored. CEL flashed when stumbling but didnt always store a code. Car stumbled at first under heavy accel at low revs but progressed over a couple months to stumble at even moderate accel at low revs. When the TPS code came up I got a Trans Prog since I have an auto. My problem turned out to be bad Bosch Platinums, 2 coils going bad and possibly bad coil boots. I replaced my TPS when I was getting this code and it didnt do anything. 2 used coils later and I'm cruising strong. I had tested the coils and the values were correct but when I swaped in a known good coil my problems were gone.

[Dave M]

I had a similar problem with my car. Same TPS code. No other codes stored. CEL flashed when stumbling but didnt always store a code. Car stumbled at first under heavy accel at low revs but progressed over a couple months to stumble at even moderate accel at low revs. When the TPS code came up I got a Trans Prog since I have an auto. My problem turned out to be bad Bosch Platinums, 2 coils going bad and possibly bad coil boots. I replaced my TPS when I was getting this code and it didnt do anything. 2 used coils later and I'm cruising strong. I had tested the coils and the values were correct but when I swaped in a known good coil my problems were gone.

Sort of dreading the bad coil scenario. It makes sense, and has been in the back of my head, but I was hoping for a cheaer solution :D . I know there are coil testing methods out there, so I'll try it, but it seems it didn't work for you. If if comes to it, where did you find used coils? I don't have access to a wrecker in town.

Thanks for your input Neil.

Dave M

[ryan roopnarine]

playboy, i have a box with 1 bremi and 3 or 4 may und christ (zundspule) coils in it, i don't know if your car has bremi, zunds, or bosch coils on it, but i can certainly send you the one bremi or two of the zunds (i think the others might have little minute cracks in them) with the rest of it. the boschs are on the car, so i can't send you those. i'd strongly suggest including the maf in your testing (as i've been there), and it doesn't really weigh anything, but thats up to you. coils might up the shipping cost of the box a bit, but they're free for you to try.

[Dave M]

playboy, i have a box with 1 bremi and 3 or 4 may und christ (zundspule) coils in it, i don't know if your car has bremi, zunds, or bosch coils on it, but i can certainly send you the one bremi or two of the zunds (i think the others might have little minute cracks in them) with the rest of it. the boschs are on the car, so i can't send you those. i'd strongly suggest including the maf in your testing (as i've been there), and it doesn't really weigh anything, but thats up to you. coils might up the shipping cost of the box a bit, but they're free for you to try.

You've got yourself a 'deal' Ryan. I'm currently running Bosch coils. I will take whatever bits you have available and gladly pay the extra shipping for the coils. I'll pm you with my shipping info.

Dave M

[ryan roopnarine]

You've got yourself a 'deal' Ryan. I'm currently running Bosch coils. I will take whatever bits you have available and gladly pay the extra shipping for the coils. I'll pm you with my shipping info.

Dave M

damnit dave, now i gotta find a box and all that crap :D

no, seriously, i just got your PM. i'll police all the stuff i can find up and see how quickly i can move. off hand, i carry a coil+boot and ICV and TPS and 1 fuel injector+ Intake air sensor and old water temp sensor in my trunk toolbox. i'll go ahead and send you all of the coils that have boots that i have (4 i think, maybe 3) so that you can take as many bosch as you need offline and know for sure. some of the spare coils i have are cracked (as in 10% chance of misfire if it is raining heavily outside) but work perfect if dry. i'd wouldn't hesitate at all to put them all on my car if i were doing diagnostics with them. ill try to get you this then:

either 3 or 4 coils
MAF
fuel injector
ICV
TPS (maybe doesn't work 100%, but OK to swap and check)
water temp sensor (a little slow, possibly)
intake air sensor

if i find anything else laying around here ill put it in.

[Dave M]

damnit dave, now i gotta find a box and all that crap :D

no, seriously, i just got your PM. i'll police all the stuff i can find up and see how quickly i can move. off hand, i carry a coil+boot and ICV and TPS and 1 fuel injector+ Intake air sensor and old water temp sensor in my trunk toolbox. i'll go ahead and send you all of the coils that have boots that i have (4 i think, maybe 3) so that you can take as many bosch as you need offline and know for sure. some of the spare coils i have are cracked (as in 10% chance of misfire if it is raining heavily outside) but work perfect if dry. i'd wouldn't hesitate at all to put them all on my car if i were doing diagnostics with them. ill try to get you this then:

either 3 or 4 coils
MAF
fuel injector
ICV
TPS (maybe doesn't work 100%, but OK to swap and check)
water temp sensor (a little slow, possibly)
intake air sensor

if i find anything else laying around here ill put it in.

Anything you need from Canada? Beaver tail? Snowball? Moose meat?

This is a huge favour and I'm very appreciative. I'll think of something.

Dave

[ryan roopnarine]

Anything you need from Canada? Beaver tail? Snowball? Moose meat?


canadian?
i need monday's toronto SUNshine (http://sunshinegirl.canoe.ca/TorontoSunshine/ssg_Monday.html) girl's beaver so that i can do something with some meat ( i couldn't figure out how to put snowball in there). i really hope that you can get everything sorted out before parts even get to you.

[bill g]

Now, when I tested all three harness pins to the strut (ground), I recorded the following (Note, my VDC was set at 20V, so I may be limited):

pin no 3 (top) negligible
pin no.2 5v
pin no. 1 negligible (this pin is earthed)

Does this mean anything to anyone?

Seems like there is something wrong with pin 3 value.
According to the BMW Electrical Troubleshooting Manual (ETM), for Motronic 3.1 M50 -

Pin no 3 (top) connects to pin no 59 at the DME (or ECU as commonly called) and should have 5V

Pin no 2 connects to pin no 12 at DME and should have 5V - this is the pin which receives the varying voltage signal (approx range 0.4V to 4.2V depending on throttle position) back from the TPS

Pin no 1 (bottom) is earthed

My own results were measured at the removable harness, ignition on.
It would really help if someone else with a known good system could check and report their voltage values to back this up.


Bill G

[ryan roopnarine]

home skillet, so far i've found that stuff plus one extra coilpack (for 5). im leaving it here for a little bit longer to see if i can find the boot for the extra coil i have (so that i can send you 6 coils). which style of fusible link do you have, the underseat one or the one that mounts on the shock tower? also trying to slim this package down, if possible, as right now it weighs 7+ lbs (its all the coils). should get it out tomorrow or thursday.

[Dave M]

home skillet, so far i've found that stuff plus one extra coilpack (for 5). im leaving it here for a little bit longer to see if i can find the boot for the extra coil i have (so that i can send you 6 coils). which style of fusible link do you have, the underseat one or the one that mounts on the shock tower? also trying to slim this package down, if possible, as right now it weighs 7+ lbs (its all the coils). should get it out tomorrow or thursday.


Supa dupa Ryan,

I used contact cleaner on the TPS and harnes, to no avail. I am interested in getting the TPS from you, switching the coils, swapping in a new DME relay (for what its worth), possibly cleaning the ICV etc. and........crossing my fingers.

Don't worry about the fusible link as I just replaced it this summer. BTW, its on the strut tower.

Thanks again, just let me know when it leaves, and what it cost.

Dave M

[ryan roopnarine]

did you put a new o2 sensor in when you put the engine back in?

[Dave M]

did you put a new o2 sensor in when you put the engine back in?

No, but the O2 is <50k miles old. I assume it wouldn't be an issue, but you never know. The fact that I'm not getting the O2 code also had me ignoring it as a source.