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Hi all , my RX-T has had this mild surging business since I bought it and I'm wondering if its TPS (throttle position switch) has been moved or is worn out .

Does anyone know by the wire colour codes how to test the continuity of the full throttle and closed throttle switches ?

I just want to remove the chance of this RX stumbling because the closed throttle contacts may be closed when the throttle is actually open possibly making it run lean at part throttle and flat spot at small throttle openings . The engine manual I have is the 2 part PDF one and I think it covers the later Pot type TPS .

Cheers Adrian .

the later pot type ? how does this differ from the 'earlier' type ?

i have read that some TPS (not specificaly subaru) can have setting issues , namely voltage at rest or idle or something that can cause problems. in these cases you need to know the position, 'conditions' such as idle or just closed with ignition on or something and adjust possy of tps to get correct volt reading. how this applies here i do not know

I think I read somewhere about there being an 'earlier' and 'later' type. I set mine up according to the '89 manual but mines an '85 so I've been kinda wondering the same thing

timmo

earlier type had no variable pot, just the idle switch, because that's what mine originally had. Replaced with a variable type,not subaru tho, just some generic Mitsubishi/nission/crumador?? generic one found at wreckers.
altho it used a Micotech, so the TPS can be calibrated.


Test the TPS pot with a multimeter on Ohm range, you should get 3kOhms constant across 2 wires, and when to one of the other should vary btw 200ohm-3kohm. Another set of wires is for the switch, and use a continuity check for go/no go as you twirl the pot. (as I recall from memory:( ), wire colors??lol, probably need to trace the wire to the ECU and compare to ECU connector pin out diagram.

Could the TPS causing the surging on my car too? I had to take it off the other engine as it was the one that came with the loom...

Cheers

From looking at both types (flapper/hotwire) TPS's the difference is that the hotwire kind have three extra wires exiting from half way down the side of the TPS unit . The extra wires go to a round plug numbered 1/2/3 corresponding to wire colours R/B/W . The manual identifies them as :

1) R - Sensor signal (control unit) .
2) B - Ground (control unit) .
3) W - Power (control unit) .

The main rectangular plug to TPS which all have and are 3 wire except the Vortex Spider TPS which has 4 .

1) LW - Control unit (idle switch) .
2) BR - Ground .
3) - -

I'm told that the early flapper engines will run off the later hotwire TPS and the white 3 wire plug is not used , I gather early ECU's don't have the circuitry for the potentiometer but if its there and unplugged the computers none the wiser .

Will get back with the Spiders unique TPS but its really a kind of doubling up of the above to no doubt simplify the loom wiring .

Cheers A .

discopotato03 wrote: Will get back with the Spiders unique TPS but its really a kind of doubling up of the above to no doubt simplify the loom wiring .

Cheers A .

Yeah you are spot on, they are the same 2 sensors, just combined
The Potentiometer uses 3 wires, Power signal and ground, and the other wire is for the idle contact that closes to the ground wire of the potentiometer.