I need some advise please - Throttle Position Sensor

SandmanEnters

New member
Hi Guys

This will be a long one, my OCD tends to kick in when talking cars. You have been warned:)

I have steadily been working to rectify the MANY problems on a 2002 BMW 330d (Auto) that I purchased last year. Previous owner must have been actively trying to see what the worst condition is that can be achieved on this awesome car.

Long story short, I am winning the battle. However, I had been experiencing some irregular throttle response for a long time. This later developed into a situation were the engine cuts out when the throttle is depressed very quickly all the way down to the kick-back switch. When running diagnostics later, Throttle Sensor Position (0120) was logged as the fault code. I was advised by a local useless mechanic that I needed to replace the entire throttle body. This was a few months ago, and I have not done this yet. Since the mechanic was wrong about everything else (When I told him what I believed the other problems were and brought him the parts to fix it, he actually laughed at me and said he's doesn't want to steal my money. Asshole. Turns out I was right btw - Thermostat stuck open, low pressure pump stuffed etc.) I decided to ignore the throttle problem for the time being.

I ended up doing a lot of the diagnosing and some of the fixing myself, aided of coarse by all the advise you guys post on here daily. Thank you for that. I am afraid I need to ask your help once again though.

The throttle cut-out happened again today, presenting with the DDE light. I had hoped that this problem might be related to some other issues and that it would be resolved after my last round of proper repairs last week, (this was done by an ex-BMW master technician who now runs his own shop). He really did a amazing job on everything I asked of him and much more that I was not even aware of.

Unfortunately, the code is back. (I had decided to do a final check for faults and pressure readings as I am getting my RaceChip Pro 2 in two days time and I want to have peace of mind that everything is tiptop before upgrading).

We cleared the code and went for a drive with the diagnostics plugged in, I put my foot down all the way very quickly and it popped up again. So that's confirmation I believe. To be clear, when depressed normally, the throttle does NOT cause the engine to cut out even when fully depressed. ONLY when doing so in a very aggressive manner does the engine cut out. It happens only for a moment or two, presenting with the DDE light, and then everything goes back to normal. Even if the throttle is kept down all the way, the engine still springs back to life and starts pulling again. I have always felt that the car seems a bit underpowered in the first three gears, and at low rpm's. This has been much better (yet still bothered me a tiny little bit in the back of my mind), since all repairs have been done, so I really hoped the problem was sorted. But it seems there is a throttle issue.

This would explain my consumption as well, which I thought was just from my enthusiastic driving the last week. However, it is still on the climb when driving normally in the city. At 12l/100km this afternoon, which simply cannot be right.

So i guess after all my yapping, my question is this:
Is the only solution for me to replace the entire throttle body or is there still some things that can be checked that I am not aware of? Throttle body is a flippen expensive part, and it will have to be ordered through the stealers if I want a OEM part.

Any advise would be sincerely appreciated, thank you.

Regards,
 

Peter@AEW

BMWFanatics Advertiser
Official Advertiser
I am guessing that the potentiometer under the pedal is loosing comms with the throttle actuator when you depress quickly.
Either a reset of the system or start by changing parts.
 

SandmanEnters

New member
a1exander said:
I am guessing that the potentiometer under the pedal is loosing comms with the throttle actuator when you depress quickly.
Either a reset of the system or start by changing parts.

Thanks for the reply, just a few questions:
1. When you say reset the system, do you mean the throttle adaptation reset (holding in pos 2 for 10sec, then off for 10sec, then start engine), or is this something completely different? I have done the former, no luck with that. (I am still learning about these things as situations present themselves, so I am still quite clueless about most procedures.)

2. Can the throttle sensor itself be replaced without replacing the entire body? (I have been informed that it can't, but I have found it's better to get to get second opinions on these things)

3.Also, if your diagnosis is correct, I assume that the throttle response is actually not what it should be at any other position either? Would it be prudent to sort this out before installing the above mentioned chip, or can I live it for a month or so without causing more damage?

Thank you for your time.
 

Peter@AEW

BMWFanatics Advertiser
Official Advertiser
The reset needs to be done by agents machine

We have tried using INPA with limited success.

The other reset methods as described in your post are of limited use and will not reset the problem you are experiencing.

The throttle sensor question I do not understand...please elaborate are you talking about the throttle actuator motor which is attached and part of the throttle body?

I guess that at some stage someone had a go at the throttle actuator and disconnected it with the battery connected.....ask me how I know or for that matter ask Flash Gordon how he knows :)
 

SandmanEnters

New member
a1exander said:
The reset needs to be done by agents machine

We have tried using INPA with limited success.

The other reset methods as described in your post are of limited use and will not reset the problem you are experiencing.

The throttle sensor question I do not understand...please elaborate are you talking about the throttle actuator motor which is attached and part of the throttle body?

I guess that at some stage someone had a go at the throttle actuator and disconnected it with the battery connected.....ask me how I know or for that matter ask Flash Gordon how he knows :)

Thanks again for the info, I appreciate it.

I assume you had a bad experience? Not the prison shower kind of bad experience, more throttle actuator related:roflol:

What I meant with the second question: In my head I see the sensor as a separate unit that attaches to the throttle body. I base this on nothing but general speculation ofcoarse. So I was wondering whether the sensor could be replaced without replacing the entire throttle body, as I have been informed the body is a very expensive part? I guess I should actually do more research on the structure of these systems before asking questions though like this though. I will get on that right away.

Also, would you mind having a look at my edited reply above please? I have added a third question regarding the RaceChip Upgrade.

Once again, I appreciate you taking the time to help.


Nikhil said:
guys just remember there is no throttle body on this car :=):

Really? Once again I should definitely do more research research before I start posting things. Thanks for the help, I appreciate it.
 

Nikhil

Honorary ///Member
Netercol or Andy can explain how it works but, there is definitely no throttle body like a petrol vehicle :thumbs:
 

SandmanEnters

New member
Nikhil said:
Netercol or Andy can explain how it works but, there is definitely no throttle body like a petrol vehicle :thumbs:

Just found diagram that does appear to agree with you, thank you for the clarification. You have definitely saved me some unnecessary confusion. This would explain the lack of info regarding the throttle body on a 330d when I did a quick search earlier.
 

moranor@axis

///Member
Official Advertiser
get a new mechanic... how can he advise replacing a throttle body on a car that has none? (BMW master technician lol)

what codes came up... this would probably help identify the probem
 

SandmanEnters

New member
moranor@axis said:
get a new mechanic... how can he advise replacing a throttle body on a car that has none?

what codes came up... this would probably help identify the probem

Hi, I have indeed gotten rid of the mechanic as stated above. New guy is the one I referred to as the master technician and he's pretty awesome, but I have not taken this problem to him yet as he wasn't available today.

I did state the error code in my original thread. Code 0120, when explaining the backstory, but I guess I didn't specify that it was the same error code today as the first time.
 

applehero

///Member
a1exander said:
I am guessing that the potentiometer under the pedal is loosing comms with the throttle actuator when you depress quickly.

+1

Use INPA to have a look at the output signal from the Throttle Pedal. If the signal drops out then it is potentially the pedal that is faulty.

Thinking about it though, it depends how the car 'cuts out'. Does it feel like it wants to stall or like a big hesitation?
 

SandmanEnters

New member
applehero said:
a1exander said:
I am guessing that the potentiometer under the pedal is loosing comms with the throttle actuator when you depress quickly.

+1

Use INPA to have a look at the output signal from the Throttle Pedal. If the signal drops out then it is potentially the pedal that is faulty.

Thinking about it though, it depends how the car 'cuts out'. Does it feel like it wants to stall or like a big hesitation?


Hi, thanks for jumping in. It feels more a big hesitation, they power cuts off completely and suddenly, and then comes back just as fast. I was just out for a drive now and now that im concentrating on the throttle, there definetely is a slight hesitation even when depressing the pedal about 60 to 80 percent aswell. Its as if the car is not sure what to do for a moment and then surges to life even if the pedal has been depressed from say 30% to 80%. My first inclination was that it almost feels like a intermittent turbo vacuum leak, but the car has been check for leaks thorougly.
 

Kish2604

Administrator
Staff member
Here is my 2cents on this one...

Firstly, Don't fit any tuning box or system till the car is running properly..

The 330D in the e46 doesn't have a throttle body,instead when depressing the accelerator the dme will signal the injectors to pump more fuel into the cylinders and the vnt blades on the turbo will close (similar to a wastegate) which will spool up the turbo, this makes the vehicle accelerate.

The p0120 code you getting is 90% related to a faulty sensor under the throttle pedal. Dirt ingress or simply wear and tear could have added to the failure.

Using the realoem website to reference,I would also clean the sensor on the pipe between the intercooler and the EGR as well as the one fitted on your intake manifold, they are surely gunked up with oil over the years. Carb cleaner will suffice here.

Please enlighten us which components were tested for leaks on the vacuum system? Were all the vacuum pipes replaced? Was the vacuum reservoir or canister also checked for integrity? This item tends to develop hairline cracks which can cause surge or delayed response.

The first item to start with would be the pedal sensor/potentiometer... They should be a dime a dozen at a breakers yard...

Keep up posted...
 

SandmanEnters

New member
Kish2604 said:
Here is my 2cents on this one...

Firstly, Don't fit any tuning box or system till the car is running properly..

The 330D in the e46 doesn't have a throttle body,instead when depressing the accelerator the dme will signal the injectors to pump more fuel into the cylinders and the vnt blades on the turbo will close (similar to a wastegate) which will spool up the turbo, this makes the vehicle accelerate.

The p0120 code you getting is 90% related to a faulty sensor under the throttle pedal. Dirt ingress or simply wear and tear could have added to the failure.

Using the realoem website to reference,I would also clean the sensor on the pipe between the intercooler and the EGR as well as the one fitted on your intake manifold, they are surely gunked up with oil over the years. Carb cleaner will suffice here.

Please enlighten us which components were tested for leaks on the vacuum system? Were all the vacuum pipes replaced? Was the vacuum reservoir or canister also checked for integrity? This item tends to develop hairline cracks which can cause surge or delayed response.

The first item to start with would be the pedal sensor/potentiometer... They should be a dime a dozen at a breakers yard...

Keep up posted...

Awesome heads up and explanation, thanks man. If you are referring to the map and maf sensors, I have cleaned both, but i will have a look again at the diagrams and make sure I am thinking of the same ones you referred too. Might do the maf again just too be sure, as this was a few months back. Regarding the turbo: A specialist had taken the whole turbo system out and checked for any leaks or problems and then reinstalled it. I dont think that the vacuum hoses were changed, as he reckoned that everything was still in good shape. I will double check this with him though. I have compiled a list of the repairs, mods and maintanance that has been done on the car in my only other thread. I will get on the pc quickly and copy it in a new post under this one.

Im glad to hear the throttle switch could possibly he sorted without too much fuss.

Thank you for the detailed post I really appreciate all the help. You guys are rockstars


Here is the the link for the page https://www.bmwfanatics.co.za/showthread.php?tid=58117&page=2 where I mention the mods/repairs and maintanance done, if anybody wants to have a look. Thanks for all the inputs guys, much appreciated. I will follow up in the morning, cheers
 

SandmanEnters

New member
Quick update: I don't think I'll have time today to test the throttle, I will defininately do this though. I have also tried to phone my mechanic. He was not available, so spoke to his apprentice. The man reckoned that the engine cutting out and high fuel consumption is due to the fact that my EGR is blanked off, and that this should not be done. This is the first time I have heard anybody claim that the EGR is a vital component in this engine. 3 pages of searching "do not bypass EGR 330d e46 m57", has not returned one entry confirming this. Every page is a guide on how and why EGR SHOULD be blanked. Does anybody have any opinions that differ from this?

Regardless, I did re-attached the vacuum hose to the EGR and went for a quick drive. As I suspected, the cut out problem still occurred when I tried to induce it by putting my foot all the way down very quickly again. It did however feel more difficult to induce the problem - took a few tries - and the car did feel like it pulled better in the first three gears, especially in the higher rev range. But this could simply be a placebo effect. Will disconnect EGR vacuum pipe again tonight to make sure.

One more thing that occured to me, could a dead fuel filter possibly be the cause of this? Replaced mine about 3 months ago with one bought from Goldwagon, so it's not OEM. I have heard of new filters being DOA, with problems disappearing when putting the old/replaced filter back.

If the throttle pedal sends a signal to the injectors to increase the amount of fuel, but the filter is not supplying enough, this could be a plausible scenario?

Thanks guys.
 

Nikhil

Honorary ///Member
Hey bud, the EGR story is bullshit I know of over 20 diesels with blanked Egrs and no issues. I suggest you pay Ross Duncan in Midrand a visit, let him have a look at your car and see what he can do. He knows his stuff and won’t give you retarded answers like your past mechanics. Was the fuel filter installed the correct way around?
 

SandmanEnters

New member
Nikhil said:
Hey bud, the EGR story is bullshit I know of over 20 diesels with blanked Egrs and no issues. I suggest you pay Ross Duncan in Midrand a visit, let him have a look at your car and see what he can do. He knows his stuff and won’t give you retarded answers like your past mechanics. Was the fuel filter installed the correct way around?

I thought as much, thank you for confirming. I will definitely give Ross Duncan a call.

I did not specifically check that the filter was installed the wrong way around, as I never thought that this could happen and still have a functioning engine? I'll will go and have a look the moment I get a chance though. Thank you for the advise, sincerely appreciated.
 
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