Resolved Throttle position - incorrect on logger

[xdxoxuxgx]

I was checking out some things on my logger today like base timing, injector duty cycle, etc. and when i was sitting still, idling, I noticed that my throttle position read 10% on the logger. It changes accordingly as I push the throttle in, but when the throttle is completely out, it stays at 10. I turned the car off, checked the actual throttle cable itself, and everything seemed fine. Does this sound like a bad TPS or something else?

 

[7"exhaust_tip]

I don't think it is a bad TPS, since I believe that is where your logger is getting the #'s from.

It probably just needs to be adjusted.

TPS Adjustment

 

[xdxoxuxgx]

Ok I'll try that, thanks. Would this have any effect on my performance?

 

[steve]

That's exactly where it should be.

The VFAQ that was linked is wrong. You adjust a 1G TPS by the output voltage with the throttle closed. It should be between 0.48v and 0.52v. The TPS is fed 5v so 0.5v is 10% and that's what your logger is reporting.

2G's are adjusted differently.

 

[xdxoxuxgx]

So 10% is normal? Well, that definitely doesn't make sense, but I won't question you Steve.

 

[steve]

So 10% is normal? Well, that definitely doesn't make sense, but I won't question you Steve.

Straight from the FSM. I highly suggest people get the Factory manuals.
That was the first accessory I bought for my car back in 91.

 

[7"exhaust_tip]

Woops, sorry about that. I could have sworn the 2g's had same procedure as 1g's.

 

[steve]

Woops, sorry about that. I could have sworn the 2g's had same procedure as 1g's.

That link isn't even close to correct for a 2g either. It should be taken down but the VFAQ site is largely static at this point.

I've posted both 1G and 2G TPS adjustment procedures here several times but I can see from a quick search that they have become lost in all the rest of the noise.

1G

On a 1G you adjust the TPS until it outputs about 0.5v on pin 2 (spec is 0.48 to 0.52v) at idle (Throttle Closed). That's the same as reading 10% on a datalogger.

2G (2G TB and TPS)

2G's critical adjustment is the Idle Position Switch that's part of the TPS.

The Factory Service 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 .4 and 1V while the feeler gauge is still in place. Anything in that range is ok as long as the IPS is adjusted correctly.

2G with 1G throttle body and a 2G TPS

From the RRE page:

Closed TP Switch and TP Sensor Adjustment [2G]

1. Disconnect the connector of the TPS.
2. Connect ohm meter between terminals 3 and 4.
3. Insert a feeler gauge with thickness 0.45mm (.0177 in.) between the 1G IPS and the throttle lever.
[Fold a piece of paper in half 4 times if you don't have the feeler -Ed.]
4. Loosen the TPS mounting bolts. Turn the TPS all the way counter
clockwise.
5. Check for continuity in this condition.
6. Slowly turn the TPS clockwise until the point where continuity and
non-continuity is found (pins 3 and 4).
7. Tighten the TPS mounting bolts.
8. Check the voltage between pins 2 and 4 of the TPS with the ignition
switch on, but the engine not started.
9. Standard value: 400 - 1000 mV
[Measure at the ECU pins or on your SAFC]
10. Remove the feeler gauge.

To assure yourself about my claims about the VFAQ on adjusting by resistance, look up how a voltage divider works and run the numbers. The potentiometer is a variable voltage divider. As used in the TPS one end is grounded (pin 4) and the other fed the +5v sensor power (pin 1) and the wiper comes out on pin 2. When running the numbers keep in mind that with a pot the total resistance of the divider doesn't change, so as R1 increases, R2 decreases.

Now if you measure your TPS and sensor voltage and then do the math you can calculate the correct resistance to give the required voltage. I don't have any problem with someone doing it that way but you can't just take some resistance number from a website.

 

[xdxoxuxgx]

Wow Steve, you've got more than enough information to back up your post haha.