After reading another variable TPS how to, I figured I'd throw up my experience with a different TPS on my 1.6L miata. I used a new Beck/Arnley TPS from a 1991 Nissan 240sx (5spd). I chose this because they are quite cheap, are super easy to find used, and they have a cable coming off of them, so it's very easy to wire it into the stock harness. Here is what the new tps looks like:
Like the stock wiring, it is a 3 wire setup. The black wire is ground, Red wire is power, and white wire is the signal. On your miata, you will have to move the TPS wire on the ECU from 2L to 2W. Here is a picture of the wiring harness:
So, here's the basic how to:
Things you will definitely need:
- Two small self tapping screws
- A Marker
- Double Sided Tape
- Some pliers and a vice (or a hacksaw)
- A Drill and a holesaw (or something to cut metal)
Step 1 - remove the stock tps and take it apart. Remove the plastic cover, and all of the little metal arms. You'll be left with the metal base, and the spinning part in the center of the base. The stock TPS looks like this:
Step 2 - it will help dramatically to have a drill press and a hole saw, but you could do this several different ways. I used a hole saw and cut the center right out of the metal base:
Step 3 - With the hole enlarged in the middle, I then went and straightened the metal base out (it has an L bend in it). I just used a vice and some pliers to get it reasonably straight:
Step 4 - put the base back on your throttle body, and screw it in. Then, get some double sided tape and put it on the new Nissan TPS. Put the new TPS onto the throttle body, and hold it in your hand while moving the throttle. Make sure there is enough room for the throttle arm to rotate completely. I found that having the Nissan TPS line up exactly with the original plate worked fine for me. Once you've verified that the throttle can move properly, push the new TPS onto the old plate so that it sticks. Unscrew the original plate and pull the two off.
Step 5 - Using a small drill bit (smaller then the self tapping screws), drill two holes (one on either side of the TPS) that go through the baseplate (you can use a marker if you want - not super neccesary, just make sure they're centered). Once the holes are drilled, screw the sell tapping screws through the Nissan TPS metal arms and into the base plate (all the way). Once they are tightened, use a hacksaw or some cutting device to cut the backs of the screws that are piercing through the original TPS plate.
Step 6 - Install your new TPS! Push it onto the throttle rod, and use the original screws to mount it.
Step 7 - Wire it up! It's pretty straight forward. The easiest way is to cut the end of the factory harness for both the miata and the Nissan TPS, and then solder / connect the wires together. Make sure you also get access to your ECU and move the tps signal wire from 2L to 2W. Your AEM EMS will have come with extra ECU pins, and they fit the stock miata harness.
Here's a pic of mine installed (please ignore the hole in the top of my TPS - long story):
***** SOFTWARE STEPS *****
Step 8 - Open your AEM Pro software and connect to the ECU. Go into Setup -> Sensor -> Throttle Position Sensor -> Options. Change the Throttle Analogue Input to TPS Voltage.
Step 9 - This Nissan TPS rotates the opposite direction of the miata, so you need to invert the voltage settings. Go Options -> Full List. Scroll down to TP RAW INVERT. Change the setting to ON.
Step 10 - Go to Idle -> Advanced Idle -> Idle Switch Input. Make sure under theadvanced idle table you have "Idle Switch Input" set to "Switch is Always OFF"
Step 11 - Go to Configure -> ECU Setup -> Set Throttle Range. Follow the onscreen steps to calibrate your TPS.
Congrats, you have a variable TPS! My car ran 100 times better with a variable. It used to be very jumpy when going on or off throttle, and is much smoother now. I hope this helps you!
Here's information you might need on finding one of these tps's:
The Beck/Arnley part number is 1580490.
Here's the application list for the TPS (must be manual transmission):
NISSAN 240SX (1991 - 1995)
NISSAN 240SX LE (1991 - 1992)
NISSAN 240SX SE (1991 - 1995)
NISSAN ALTIMA 1993
NISSAN ALTIMA GLE (1993 - 1995)
NISSAN ALTIMA GXE (1993 - 1995)
NISSAN ALTIMA SE (1993 - 1995)
NISSAN ALTIMA XE (1993 - 1995)