eye of ra

My throttle is only working up to about 28%

It is a smooth increase till that point but any further movement of the accelerator is ignored.

I have no engine light or codes and provided I don’t go above 28% or press the kickdown it drives OK.

Is this likely to be the Throttle Position Sensor or the Throttle Body Actuator? I don’t know where the scan tool reads from.

Or could it be something else? Any help would be appreciated.

Plutoe

If you are looking for the correct answer, you will get the car scanned. If you are looking for a date or want a finger in the wind answer, then change em both. Maybe you will get lucky with PA money for both!

eye of ra

If you read my post it says “I have no engine light OR CODES” I did think about using my finger to decide if I had codes but chose to scan it instead.

Moving forward my question is what does the scanner read when its quotes the percentages, the TPS (most likely bearing in mind the name) or the TBA. I will find this out when I work on the car this weekend but would have saved me time if someone else could have confirmed.

The added information was in case someone out there had had the same problem and could given a quick solution.

There is also no reason for a code because as I stated the car drives normally (my other post has been sorted) so as far as the car (ECU) is concerned I could be a 90 year old granny that never presses the accelerator over 28% so why would it give a code.

Silver_Arrows

Try having someone press the accelerator pedal and see if there's a physical issue with the cable, it' the low tech thing I'd try first since you're not getting code errors or and there's no engine light. A physical restriction would explain that at least.

eye of ra

Thank you for the advice.

Having now done some research on electronic throttle controls it would appear I may have been calling things by their wrong names.

What I was calling the TPS would be better called the Throttle PEDAL position sensor and the TPS is part of what I was calling the throttle body actuator.

I have moved the TPPS by hand and as with the pedal the scan tool shows a steady percentage increase till about 28% after that as you move it further there is no increase in percentage.

As I have no codes my theory is the TPPS not the TPS or Actuator. However before throwing money at it does anyone have the voltage and/or resistance values of the terminals?

From what I understand all W208 where the same but if it helps it’s a 2001 430.

Serndipity

Did you see this thread http://www.benzworld.org/forums/w163...-test-tps.html ?

Note the MB WIS info in post # 5 .

A faulty pedal position sensor would store a P1542 diagnostic fault code. I believe our W208s use the Hall Effect sensor and trouble shooting is via voltage (not resistance) measurement. I've included some additional on this.

insame1

I doubt you have a STAR scanner. If you did you would know what was wrong.

myworld

Get a better scanner. I have a little bosh one. I thought it was good, but should have got Carsoft. Too much guessing with the cheapies.

cindyclk

pay to get star scan

eye of ra

Thank you for that information that is exactly what I needed to eliminate the Pedal Position Sensor as the problem.

I managed to find some info elsewhere on the Throttle Body/Throttle Position Sensor and came to the conclusion that something in-between was at fault.

While searching for the reason for my fault I discovered why I didn’t have a code, because I don’t have a fault, it’s a “feature” when in neutral the throttle butterfly movement is restricted as a rev limiter to protect the engine when not under load. Took the car for a drive with the scanner connected and throttle position went to 100%.

I was assuming the 28% throttle when tested in my garage was a fault and causing my lack of power while driving, when it wasn’t.

Turned out the lack of power while driving was the cheap ebay MAF I purchased when I did have an engine light and code.

So my problem was sorted without wasting money (except the c**p MAF) with the help of one or two people here who genuinely wished to help (Carsoft does look interesting) and I wish to thank them, along with some searching and a genuine MAF.

Investigation should be the first thing you do. If the FIRST piece of advice is spend/waste money at the dealer why not just answer all questions with “take your car to your local dealer and they will fix it”. I accept if after some investigation you are getting nowhere a Star scan is probably a good idea.

insame1

I am glad you found the answer to your problem.


I would not suggest that you take a car to the the dealer for repairs. I for one don't like to buy parts I don't need. In a situation like yours a STAR scan would point me to the problem or at lest the right direction. The dealer has a scan system that is far superior to any OBD scanner. Even if you are not seeing a light or a code there is much stored info you can not access with a OBD scanner. I have actually caught things on the STAR scan the indy did not pick up on and saved me thousands. Also you have to admit that someone who works on MB for a living is probably better suited diagnose a complex problem than your average armchair mechanic.