Throttle Position Sensor - how to calibrate?

[CorvallisBMW]

After talking with Brody from Miller about how my engine is down on power, he suggested checking the TPS for proper function. He mentioned that M1.3 cars have 3 wires, and that at WOT there should be continuity between the brown/black and ground. I checked mine and it seems like that's what I've got:


brown-blue to ground has continuity at closed throttle
brown-black to ground has continuity at WOT
Between wires has continuity at closed throttle, ~18K ohms at partial and 115 ohms at WOT

I know there's a audible "click" that can be heard from the TPC near the closed position, but I'm not sure if it should click just as I open the throttle, or should it happen somewhere else?

Does this seem right? The e34 Bentley has good info on page 130-8 and I think it all checks out.

[bmwguy325is]

So down on power is your main concern? I just replaced a TPS. It still clicked and checked out on the ohms. However when in operation it did stick. Its fairly easy to replace.
Did you check the ohms with the correct amount of gap with a feeler guage?

[bmw335isturbo]

Dam

hey I wish I was still their I could do it for you real quick, but I think your tps might be the problem do you have another to check?

[CorvallisBMW]

I don't have a spare to check, but I'll try and track one down this week. There's a U-pull close by my new place.

[bmwguy325is]

I don't have a spare to check, but I'll try and track one down this week. There's a U-pull close by my new place.

New part is $40 bucks

[Doughnut]

Before the audible "click" (fully counter-clockwise) is the idle position.

[CorvallisBMW]

So as I open the throttle, I shouldn't hear the click, correct? I tried setting it the other way (so it clicks just as the throttle opens) and my idle jumped to 1700rpm.

I found a lot of good info on mye28.com about how to adjust both the throttle plate and the TPS. I'm going to give both of them a try this afternoon.

New part is $40 bucks

where's that? blunttech, pelican and autohausaz are all ~$80

[nando]

So as I open the throttle, I shouldn't hear the click, correct? I tried setting it the other way (so it clicks just as the throttle opens) and my idle jumped to 1700rpm.

I found a lot of good info on mye28.com about how to adjust both the throttle plate and the TPS. I'm going to give both of them a try this afternoon.




where's that? blunttech, pelican and autohausaz are all ~$80

it should click just as you open the throttle (don't adjust it too tight!). that is the switch going from "idle" to "part throttle". there is another switch at WOT but if your idle switch is set correctly WOT should work too.

[CorvallisBMW]

^setting it like that caused my car to idle SUPER high. I'll try adjusting the throttle plate first, then the TPS. maybe the throttle plate isn't closing enough, causing the idle to be high.

[nando]

the throttle plate should just be closed. it's not used for idle at all.

if you adjust the TPS too tight it will go straight to part throttle. try adjusting it so that the "click" is at like 50% throttle (just for testing). If it won't idle properly with the TPS tripping an idle state, then the problem isn't the TPS.

and technically, at part throttle the ICV closes completely. if you set the TPS so it never clicks to the idle state, the engine should stall.

1700rpm is probably max open for the ICV (50% duty cycle). That's what it sounds like it's doing - idle is being tripped properly, but the ICV is going to 50% DC and causing your idle to rise. your TPS is likely working fine, as is the ICV, but the DME is
telling it to open the ICV all the way.

Try unplugging the ICV and see if it holds an idle, before you adjust your throttle.

you wouldn't be the first person with idle issues on the MAF/WAR combo..

[CorvallisBMW]

According to everything I can find on mye28, the throttle is suposed to be 0.002" open at idle, allowing some air past so that the ICV doesn't have to do all the work. http://www.mye28.com/viewtopic.php?t=95158

Is it just me or is this a bit confusing?

[CorvallisBMW]

OK I pulled off my TB and checked out the clearance between the throttle plate and the bore walls. I'd say there's about 2 thou of gap, and the anti-tamper paint is still on the idle stop adjustment screw.

I also made a mistake earlier when I said that when setting the TPS to click just as the throttle opens/closes causes my idle to go high; it's the opposite. When I set it to the click never activates (i.e. the throttle would have to go past the full-close position to make the click) that sends my idle sky-high. Which seems backwards; shouldn't that deactivate the ICV when under part-throttle and cause the idle to drop?

Anyway I've noticed I have a very lumpy idle when cold, but it smooths out once warm (though it seems pretty high at 900rpm). Occasionally it will hang and end up idling at like 1600, but that's rare. I've changed out the CTS so I'm leaning towards the possibility of this TPS being faulty.

[CorvallisBMW]

OK so I did some more testing and this is what I found:

Between pins 2 and 18:
closed (0 ohms) at idle, open at WOT
0 VDC closed, 1.33V at WOT

Between pins 18 and 3:
open at idle, open at WOT (should be closed per Bentley)
1.33 VDC at idle and WOT

According to what I've read on mye28, I should be seeing 5 VDC across the circuit... what would cause the voltage to be low like that?

Either way I wonder if my TPS is no good since the circuit doesn't close at WOT

[Doughnut]

Either way I wonder if my TPS is no good since the circuit doesn't close at WOT

Quickest way to find out is to get a known working one and see if it makes a difference. Though I'm starting to believe your problem is a combination of things.

Audible "click" should be adjusted so it happens as soon as the throttle is cracked open.

[nando]

OK so I did some more testing and this is what I found:

Between pins 2 and 18:
closed (0 ohms) at idle, open at WOT
0 VDC closed, 1.33V at WOT

Between pins 18 and 3:
open at idle, open at WOT (should be closed per Bentley)
1.33 VDC at idle and WOT

According to what I've read on mye28, I should be seeing 5 VDC across the circuit... what would cause the voltage to be low like that?

Either way I wonder if my TPS is no good since the circuit doesn't close at WOT

unplug the TPS and turn on the ignition. see if you're getting 5v at the connector.