How can I adjust the Throttle Position Sensor on my 3.5 - PeachParts Mercedes-Benz Forum

werminghausen · #1 02-12-2011, 02:53 PM

I have my TPS open and wanted to adjust it but couldn't find out how this works. I have seen that there are different ones. Mine has no numbers at the 4 leads. I read that there is a switch that has no continuity when throttle is closed and continuity when it opens 0.4mm.
1) I tested with the 2 middle pins at the socket but I am not sure (see pic). If these are the right pins to measure (the two in the middle) then the one lead is connected to the 10 step sliding contact and the second is right next to the constant sliding contact (shown in the upper right of pic 1680).
I can adjust the 0.4mm (when continuity shows up) by turning the unit on the butterfly housing.
If the throttle is completely closed the two points on the bottom right of pic1680 are open....and when I open the throttle slightly then the points close and continuity appears. So with the 2 middle leads at the socket I am measuring the described scenario but I am not sure if this is correct.
If I move the butterfly a bit further then the sliding contact moves to a dead zone and continuity is lost until the next 'tooth' of the 10 contacts is reached. Continuity goes on and off for 10 times until full throttle is reached.
Can someone confirm if I am doing the right thing?

2) On the left side of pic 1680 there are 2 blades which have contact when butterfly is closed and these contacts open approx. when the points of the right side close. The 2 blades can be adjusted with a screw. The question is what is the setpoint when this contact opens?

I am happy if there is someone who could help me here.

Mike D · #2 02-12-2011, 07:04 PM

You don't have a throttle position SENSOR. You have a throttle position SWITCH. There is no adjustment. It is a series of "on/off" not resistance.

werminghausen · #3 02-12-2011, 09:14 PM

Quote:

Originally Posted by Mike D

You don't have a throttle position SENSOR. You have a throttle position SWITCH. There is no adjustment. It is a series of "on/off" not resistance.

Thanks. I wonder why you say there is no adjustment because there is a longhole with degree marks on both connecting screw connections for one reason I guess.
There are 4 leads in the socket. Who has a manual how to adjust this thing?

Mike D · #4 02-13-2011, 06:54 AM

Let me clarify my "no adjustment" statement. You can adjust for the initial setting, when the first contact strip is engaged but there is no other adjustment such as, "full open at THIS position" etc.

GGR · #5 02-13-2011, 07:45 AM

I went through this some time ago. Here is the thread: My 3.5 is "trailer hitching"

Graham made a nice write up about this: My 3.5 is "trailer hitching"

Don't get mislead by the last posts, I was reading the ohmeter the wrong way (I'm better with nuts and bolts than with electrics).

werminghausen · #6 02-13-2011, 08:20 AM

Thanks,

Tomguy stated in one of the threads you refer to: "I would think all D-Jets are the same... It should be a short on pins 12 and 17. A short is 0 ohms. Closed circuit. When the throttle is open slightly (1° per manual) it should read infinite - open loop. I have a 3.5 TB in my hand right now (only emissions difference - no idle air circuit on the 3.5 and no full throttle enrichment either). The pins read 0 ohms when it's adjusted right. The only thing I notice is that if it's adjusted too far in either direction it does NOT read 0 ohms fully closed, it will read 0 ohms slightly opened but then infinite past it, or it will never read 0 ohms. I don't recall the 4.5 sensor doing that (never reading 0 if too far "In")

GGR is saying the same thing: ""The resistance between these pins should be zero when the throttle is against it’s stop. If the throttle is slightly opened (1 degree or 0.4mm feeler under stop), the resistance should go to infinity"

I think this is same as manual which says:

at position "1." Throttle valve switch at idle (closed) - Nominal value "0".
at position "2." Throttle valve slightly open (1° or 0.4mm) Nominal value "∞"

So my interpretation is that I measured the wrong thing initially with the 2 middle .
When throttle is at a stop resistance should be Zero meaning continuity (or closed loop). This then must be the switch on the left side of my picture
1680. (I'll upload it again).
If this is correct the resistance then must be measured on the upper 2 leads, which must be then 17 and 12 as Tomguy is stating. Unfortunately my pins are not labeled.

My question is now: how are the throttle switch (17/12) and the other 10 step switch related or dialed in....Or the other way around: It seems that the 2 blades on the left side (the throttle switch) are bent a bit to the left (don't know why). If these blades should be straight then the other 10 step switch would not be correlating to the throttle switch as it should.
I could bend the throttle switch blades back to straight. What do you think?

werminghausen · #7 02-15-2011, 10:43 PM

I still need your input here! Who knows about this throttle switch and how to adjust it? Please help. Martin

Benz Dr. · #8 02-16-2011, 12:54 AM

Remove the whole throttle body to any adjustmemts.

The first thing you need to do is clean the throttle bore so that there's no carbon on anything. Once you have that done close the butterfly and see is it goes tight or not. It should have a very slight bind or grab when fully closed. If it doesn't adjust the stop screw a small amount until it does and then lock it in place.

Below all the wavey lines on the printed circut board on the throttle switch is the last quadrant or line. As long as the bottom finger sits right on top of this bottom line it should work OK. That's all I do to them aside from testing the vacuum ports for the distributor - they're often plugged.

Once the engine is running and warmed up try moving the knob on the ECU. If the idle speed changes your trottle switch is probably adjusted OK and working properly.

werminghausen · #9 02-16-2011, 07:26 AM

Quote:

Originally Posted by Benz Dr.

Remove the whole throttle body to any adjustmemts.

The first thing you need to do is clean the throttle bore so that there's no carbon on anything. Once you have that done close the butterfly and see is it goes tight or not. It should have a very slight bind or grab when fully closed. If it doesn't adjust the stop screw a small amount until it does and then lock it in place.

Below all the wavey lines on the printed circut board on the throttle switch is the last quadrant or line. As long as the bottom finger sits right on top of this bottom line it should work OK. That's all I do to them aside from testing the vacuum ports for the distributor - they're often plugged.

Once the engine is running and warmed up try moving the knob on the ECU. If the idle speed changes your trottle switch is probably adjusted OK and working properly.

Thanks. It is very kind to receive precise information.

I understand the butterfly and mine is clean and does exactly what you are describing.
I need some more help with the switches: Are you saying that at a idle stop the finger (on the right side in my pictures) should be touching the last line
and at the same time when opening the butterfly 0.4mm the left side switch should open?

Benz Dr. · #10 02-16-2011, 11:56 AM

Quote:

Originally Posted by werminghausen

Thanks. It is very kind to receive precise information.

I understand the butterfly and mine is clean and does exactly what you are describing.
I need some more help with the switches: Are you saying that at a idle stop the finger (on the right side in my pictures) should be touching the last line
and at the same time when opening the butterfly 0.4mm the left side switch should open?

Yeah, I guess that's what I'm saying. The switch does this on its own due to the way it's designed. As long as the bottom finger touches the bottom line it's adjusted correctly. I've never had to move or adjust the actual switch before although I've made adjustments to the throttle valve.

werminghausen · #11 02-16-2011, 05:32 PM

Thanks,
Do you think the precise correlation between the 2 switches is important?
I assume that there are 2 switches (one left side and one to the right of the 'distributor' which is connected to the butterfly axle.
The finger sliding on the 10 step arc is related to the second switch on the right side.

I'll try the following

A)at idle stop:
1)adjust that the finger rests exactly on the last line for continuity there
2) And left switch is closed
3) and right switch is open

B) butterfly slightly open 1 degree / 0.4mm feeler at stop

1)left switch is open
2) and right switch is closed

What I am unclear is B2 operation? is the right switch already closed is this position or does it open slightly later?

werminghausen · #12 02-16-2011, 10:38 PM

update

I have done the following adjustment now
1) I have set adjustment 2 (rotating entire unit) so that the sliding contact arm at the last bottom bar of the arc circuit board at idle stop (just as in my picture). Fixed the 2 7mm hex screws in long holes.

2) I adjusted Switch A(idle switch) by opening the slotted screw and rotated Switch A (while having the 0.4mm feeler gauge in)until switch opened.

3)With this adjustment I measured when Switch B opened when opening the butterfly. Switch B closed exactly at the point when Switch A (idle switch) opened ( at the 0.4mm point)
Does any one have a comment?

ABDow · #13 09-24-2012, 11:47 PM

Have just replaced my old TPS on a 3.5, adjusted it to the Bosch specs (including continuity at idle) and the car is running well, except for one thing - when I take my foot off the gas the engine goes full lean (I have a wideband sensor) as if the engine is getting no fuel at all. This means that the engine effectively dies until it reaches just above idle speed when it catches again with a jerk. I read a reference to the 'idle stop' in the 'trailer hitching' thread, and that this could be the problem but was not quite sure what was meant.

Any suggestions of the reasons and a cure?

Alastair

werminghausen · #14 09-28-2012, 01:10 PM

Quote:

Originally Posted by ABDow

Have just replaced my old TPS on a 3.5, adjusted it to the Bosch specs (including continuity at idle) and the car is running well, except for one thing - when I take my foot off the gas the engine goes full lean (I have a wideband sensor) as if the engine is getting no fuel at all. This means that the engine effectively dies until it reaches just above idle speed when it catches again with a jerk. I read a reference to the 'idle stop' in the 'trailer hitching' thread, and that this could be the problem but was not quite sure what was meant.

Any suggestions of the reasons and a cure?

Alastair

Hi Alastair,

my 3.5 does exactly the same thing after adjustment. Did you find a cure?
Appreciate your comment.
Martin

Frank Reiner · #15 09-28-2012, 02:22 PM

Re: Posts #13 & 14

You have both observed proper operation of the D-jet ECU in closed throttle coast-down. Fuel is cut off above ~ 1800rpm when closed throttle is sensed. Injector pulses are restored at ~ 1200rpm, or when the throttle is again opened. If a jerk is felt when pulses are restored, it is due to a leaking bypass air valve, or the ECU restoring the pulses at too low an RPM.