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2G How to Adjust the Throttle Position Sensor (TPS)

knochgoon24

DSM Wiseman
6,137
85
Jan 29, 2008
Troy, Michigan
Ok, so I just replaced my throttle shaft seals and my scribe marks aren't enough to help me get the TPS lined up correctly. When in park, the RPM will go from 1100 then slowly climb to over 2000.

I found this post, but I'm not sure I understand it correctly:

From what I can tell 2G's TPS adjustment procedure is different than what I've posted for 1G's.

2G's critical adjustment is the Idle Position Switch that's part of the TPS.
The manual has you place a 0.0177" (0.45mm) feeler gauge between the stop screw and the throttle pulley to open the butterfly and then adjust the TPS right to where the IPS (pins 3 and 4) switches from closed to open. Then they have you verify that the TPS (pin 2 and 4) reads between 0.4 and 1.0V while the feeler gauge is still in place.
Anything in that range is ok as long as the IPS is adjusted correctly.
There is no way to adjust the TPS voltage independently of the IPS on a 2G that I can see.

So if I understand correctly:
1. Loosen the 2 TPS bolts.
2. Put a feeler gauge of 0.0177" under the stop screw
3. Turn the car to the ON position
4. Rotate the TPS until pins 3 & 4 lose continuity (open)
5. Verify that the voltage between pins 2 & 4 is .4-1 volt with the feeler still in.
6. Tighten TPS bolts and remove feeler gauge.

Am I correct?
 

steve

DSM Wiseman
14,473
1,401
Feb 3, 2002
St. Charles, Illinois
Unless you have at least three hands you need some sort of small alligator clips to attach the leads to the pins on the TPS connector for the continuity measurements.

For step 5 you have to have the TPS connected and the ECU turned on and as you note it's difficult to reach the pins at the TPS so you either need to use some pins to reach the wires, or a logger to read the value.

If you had followed the link in the first post of the thread you would have seen the answer from the factory manual pages and seen the special wiring harness they use.

 

mmnuc3

Probationary Member
10
6
Feb 27, 2022
Florida
Unless you have at least three hands you need some sort of small alligator clips to attach the leads to the pins on the TPS connector for the continuity measurements.

For step 5 you have to have the TPS connected and the ECU turned on and as you note it's difficult to reach the pins at the TPS so you either need to use some pins to reach the wires, or a logger to read the value.

If you had followed the link in the first post of the thread you would have seen the answer from the factory manual pages and seen the special wiring harness they use.

I see that now. I'll jerry-rig a special tool. I appreciate the input everyone!
 

ec17pse

Freelancer
5,456
2,754
Nov 1, 2008
London, UK, Europe
Unless you have at least three hands you need some sort of small alligator clips to attach the leads to the pins on the TPS connector for the continuity measurements.

For step 5 you have to have the TPS connected and the ECU turned on and as you note it's difficult to reach the pins at the TPS so you either need to use some pins to reach the wires, or a logger to read the value.

If you had followed the link in the first post of the thread you would have seen the answer from the factory manual pages and seen the special wiring harness they use.

I have never set any of mine with the ecu connected. Just unplugged and set to .63 volts. I done a few like this as i rebuilt a few TB's and swaps etc and its always worked good. I might re read it again but not sure why the ecu needs to be on. But i shall re read it incase i missed something
 

steve

DSM Wiseman
14,473
1,401
Feb 3, 2002
St. Charles, Illinois
I have never set any of mine with the ecu connected. Just unplugged and set to .63 volts. I done a few like this as i rebuilt a few TB's and swaps etc and its always worked good. I might re read it again but not sure why the ecu needs to be on. But i shall re read it incase i missed something

This is exactly why we have these threads. On a 2G the IPS switch point is the adjustment not some TPS voltage or a resistance.

DSMLink will let you simulate the IPS for a variety of reasons starting with throttle bodies that required things like a Mustang TPS that didn't have an IPS. So while setting the 2G TPS by voltage kind of works on DSMLink, it doesn't work at all on a stock ECU where as setting the 2G TPS the factory way via the IPS switch point works on stock ECUS and with DSMLink.

So, let me ask, right or wrong for setting the TPS, just how you set the output voltage to 0.63 volts without the ECU connected or turned on to provide the +5v sensor voltage? It only does so when attached and powered up.
 

ec17pse

Freelancer
5,456
2,754
Nov 1, 2008
London, UK, Europe
So, let me ask, right or wrong for setting the TPS, just how you set the output voltage to 0.63 volts without the ECU connected or turned on to provide the +5v sensor voltage? It only does so when attached and powered up.

I followed some ones how to and used a multi meter on the TPS and clipped it to the connectors required, thats how i remembered doing it at least, i built 3 TB;s before i even installed V3 so I had to of done it some how and got it right? im now trying hard to remember what I did to be more specific but i know it was on the workbench and NOT on the car as per the instructions i was told so i went by that. my last TB rebuild was my evo 3 unit i done 3 odd years back i think and i preset that before link was installed.

I have not read back up on it but im going to have to see if i logged the thread i followed to get where i got

im wondering if i set it via resistance then, i cannot find what i used previously so not sure if its from the swap over but i might also forget what one it was. i followed something and did it a few times. since i got no proof just void my comments for now then to be safe LOL
 
Last edited by a moderator:

1990TSIAWDTALON

Moderator
9,146
4,975
Nov 14, 2013
Independence, Kansas
I'll admit I haven't followed along close because Steve has a good handle on it but I have never had an issue with key on, throttle closed, adjust for .63-.64vdc and check for 4.8xx+ WOT and leave it. The 2g is not my expertise so I'm sorry if this comment doesn't apply one bit.
Boy, where is Brett right now??? ROFL
@GST with PSI do you have any advise for this thread. :)
 

steve

DSM Wiseman
14,473
1,401
Feb 3, 2002
St. Charles, Illinois
I have never had an issue with key on, throttle closed, adjust for .63-.64vdc and check for 4.8xx+ WOT and leave it. The 2g is not my expertise so I'm sorry if this comment doesn't apply one bit.

If you want to do that on your 1G, knock yourself out. The 1G ECU doesn't get unhappy until the TPS voltage drops below 0.42V or if the IPS stays closed above some voltage I don't remember offhand and nor motivated to go look up in the code. It gets really unhappy if the TPS has dead spots, makes fuel cut seem passive.

The issue here is about how difficult it is to adjust the 2G TPS according to the factory spec and all the myths about how you can avoid doing so.
 

waltah

Proven Member
315
133
Mar 2, 2011
fairfield, Virginia
The factory spec is that the IPS should open when there is 0.45mm (0.0177") of space between the fixed SAS and the throttle lever.
There's a wrinkle, though. That spec is correct and will work for a low/medium miles throttle body. High miles cars can have enough wear on the shaft and body that setting up the switch 'by the book' will lead to it not working correctly.

I learned this on my '93 Expo LRV with 245,000.

Rather than set per the manual, what I do now is rotate the TPS in the opposite direction from the way the throttle opens until there's no continuity between pins 3-4. Then open the throttle by hand and let it close and without touching it or putting a shim in or anything rotate the TPS in the direction the throttle opens until barely beyond where there's continuity. Tighten the screws and check that the switch goes open with just a little throttle opening and closed again every time when you let the throttle close.

It may take a couple of tries to get this right because tightening the screws can change the adjustment slightly.

There's a higher level of understanding this system that may help. When the throttle is closed, the ECU controls idle speed for you. This includes the right basic idle --- 750 or 850 RPM depending on your car model -- but also 'idle up' (100 RPM more) when the A/C clutch is engaged and instantly correcting when the power steering pump or alternator puts on a load. In addition when you're driving and suddenly take your foot off the gas the ECU eases the RPM down to idle so the car won't stall when you come to a stop sign. (Called 'dashpot function.')

The idle position switch tells the ECU "You are in charge now." If the ECU doesn't get that signal when the throttle is closed it will not take control and you will have problems in each function listed above -- Idle RPM unreliable (depends on how warm the engine is, etc.), A/C doesn't work well and may bog down the engine, and car may stall when you come to a stop unless you ride the gas pedal. THE SWITCH MUST BE ADJUSTED TO CLOSE EVERY TIME, JUST AS THE THROTTLE CLOSES.

When you put your foot on the gas pedal, the switch must open promptly or the ECU may try to fight the extra air you're trying to give it, leading to surging when you start off very gently.

The mechanical air adjustments -- the throttle stop screw and BISS screw -- are set just for the purpose of allowing the ECU to properly manage the amount of air for a correct idle. They cannot be used to change the idle RPM if you want to have a smoothly running car. There's a procedure in the book for adjusting them and it's worth doing the one for the BISS because almost all our cars have by now been diddled by someone who didn't know how.

If you actually want to change the idle RPM you must change the ECU meaning having a programmable unit and probably chasing other consequences of doing so.
 

waltah

Proven Member
315
133
Mar 2, 2011
fairfield, Virginia
I just hooked up Evoscan and adjusted it until the Idle Position Switch to closed. Does this work too? 11.76% throttle position.
It'll work fine as an alternative to using an ohmmeter to adjust the Idle Position Switch but since EVOScan is on my laptop it's in the passenger seat and not as convenient as the ohmmeter. Excellent as a double check though, afterward. Closed when foot off the gas, goes open as soon as you move the pedal. I think '1' is closed, '0' is open?
 

GST with PSI

DSM Wiseman
2,696
1,433
Jul 27, 2005
San Diego, California
@GST with PSI do you have any advise for this thread. :)
Sadly, nothing to add outside of what Steve has already beat to death. It's been decades since I've had to configure a TPS without ECMlink, and even longer since I've had to mess with a 2G TPS. Most people use the "close enough" methods simply because the factory procedure is difficult to do.
 
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steve

DSM Wiseman
14,473
1,401
Feb 3, 2002
St. Charles, Illinois
Sadly, nothing to add outside of what Steve has already beat to death.

Are you sad because you don't have any thing to add or because I've beaten this topic to death? I know I'm the latter... :)
 
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