M45 Posted May 29, 2008 Share Posted May 29, 2008 I suspect the TPS may be a cause of bad jerkiness. I've already rough tested the throttle switch and it passes. How do I arrange to make the resistance test (for smoothness over the range)? The manuals say to "backprobe" the throttle sensor connector, which I assume means to shove the meter probe tips into the connector where the wires go in. However, there doesn't seem to be room for that. Plan B is to separate the connector but, like most cars, the connector is overly difficult to open. Is there a special tool one can buy for this? Usually connectors are in barely accessible places and it is impossible to get a good grip or leverage or a reasonable way to depress the tabs. Is there an easy way to open them with standard tools? Quote Link to comment Share on other sites More sharing options...
Gloyale Posted May 29, 2008 Share Posted May 29, 2008 The back of the wires (where they enter the connector) is sealed with a rubber gromet. You can just push the tip of you're meter probe right down through it. Also, If you cut the zip tie holding that main harness to the fuel rail, you should be able to pull that connector out to more easily unhook it. Quote Link to comment Share on other sites More sharing options...
Scarpachy Posted June 9, 2008 Share Posted June 9, 2008 I am in search of a TPS right now for my RX Turbo. The contacts inside the tps wear out. And the main connector on top of the tps gets full of water and corodes the terminals. I drilled the rivets off of mine, and cleaned the contacts, it helped for a little while. But, the problem is the contacting plate inside gets worn out, and it breaks connection at certain points in the rotation of the throttle. It jerks when it loses connection on or off the throttle. And if you hold steady throttle at the worn spots, it will lean out your fuel and cause it jerk of starve upon acceleration depending how bad it is worn out. Doesn't mean this is your problem, could be numerous other things. But I have had three of these turbos all with the same issue. Good Luck. And if you find one that matches my two connector 87 Rx Turbo, let me know. Good Luck Quote Link to comment Share on other sites More sharing options...
garner Posted June 9, 2008 Share Posted June 9, 2008 Should be that the black is ground, the white should be voltage coming in to the sensor when the car is on, and the red should vary with throttle possition. Could be a wiring issue rather than the sensor itself. garner Quote Link to comment Share on other sites More sharing options...
daeron Posted June 10, 2008 Share Posted June 10, 2008 I've been thinking about this...... I haven't run out to the junkyard with a multimeter, but all throttle plates open up about the same... Why can't we just find a TPS, say, off of a Nissan that would work??? There HAS to be a valid substitute for the Subaru part on this one; its just Hitachi FI and LOTS of cars use Hitachi components... I know an early 90s maxima uses a two plug style TPS, with three wires on one plug for throttle position, and then two wires separate for an idle switch. I'm not sure what the resistance values would be on that PARTICULAR unit... but what about a legacy piece? Any thoughts? I have to borrow a good DMM from my dad to get to work on my Z car sometime soon anyhow, so if I can remember to take it on a trek to the JY I will do some investigating, but I'd love to hear criticism (or support) for this idea. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted June 10, 2008 Share Posted June 10, 2008 Why can't we just find a TPS, say, off of a Nissan that would work??? There HAS to be a valid substitute for the Subaru part on this one; its just Hitachi FI and LOTS of cars use Hitachi components... I know an early 90s maxima uses a two plug style TPS, with three wires on one plug for throttle position, and then two wires separate for an idle switch. I'm not sure what the resistance values would be on that PARTICULAR unit... but what about a legacy piece? I used an early subaru switch type Turbo TPS on an 80 Jag XJ6. That Maxima one sounds pretty closed to right. But there are 2 main issues. 1: Does it rotate the proper direction??? 2: Does it output in the same resistance range?? BTW, Legacy TPS outputs in a different range, won't work. Quote Link to comment Share on other sites More sharing options...
daeron Posted June 12, 2008 Share Posted June 12, 2008 I used an early subaru switch type Turbo TPS on an 80 Jag XJ6. That Maxima one sounds pretty closed to right. But there are 2 main issues. 1: Does it rotate the proper direction??? 2: Does it output in the same resistance range?? BTW, Legacy TPS outputs in a different range, won't work. thanks for pointing out rotational direction, IIRC thats been mentioned as a sticking point before. I've got some boneyard time ahead of me with a multimeter anyhow.. I have the SPFI info handy but what are the specs for the MPFI unit thats different? I know it had a second plug on it but really don't know enough to compare to a potential substitute by any means.. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted June 12, 2008 Share Posted June 12, 2008 thanks for pointing out rotational direction, IIRC thats been mentioned as a sticking point before. I've got some boneyard time ahead of me with a multimeter anyhow.. I have the SPFI info handy but what are the specs for the MPFI unit thats different? I know it had a second plug on it but really don't know enough to compare to a potential substitute by any means.. On the MPFI units, there are really only four wires (5 but 2 are grounds that tie toghether just inside the harness so they are really like one). In fact *spider* TPS has just four pins in one connector, but outputs in the same range, but oppositte rotation. So any substitute must have: 1. an idle switch with contact when throttle is closed. 2. Potentiometer type, (3 wire; pwr,grnd,signal) 3. Output range from between 5.8-17.8 K ohms throttle closed between 1.5-5.1 K ohms throttle open 4. Must be a working unit with smooth resistance change over the whole range. An Analog Multimeter is best for this test because you can watch the needle sweep. Quote Link to comment Share on other sites More sharing options...
Sonicfrog Posted June 13, 2008 Share Posted June 13, 2008 And not all Subie TPS's are wired the same. I bought a used engine with intake included. That TPS has three wires on top, while my TPS has two wires on top and two on a harness coming out the side. I guess the same people who were deciding on distributors were also in charge of the TPS department. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted June 13, 2008 Share Posted June 13, 2008 I guess the same people who were deciding on distributors were also in charge of the TPS department. No it's a model year thing, early (85,86,early87 XT) and later (late 87-91 everything) The above postings are all in refference to the later style This is speaking strictly of the MPFI TPS setups. IIRC, the SPFI are all potentiometer type, 4 wire. Different output range than the MPFI, but all the same 86-94 Quote Link to comment Share on other sites More sharing options...
salewit Posted June 25, 2008 Share Posted June 25, 2008 The manuals say to "backprobe" the throttle sensor connector, which I assume means to shove the meter probe tips into the connector where the wires go in. However, there doesn't seem to be room for that. What I do is take a straight pin and stick it in there between the wire and the connector and probe the pin. If you don't have a pin, a safety pin, or possibly an uncoiled paper clip might fit in there. The connectors on my 92 Legacy would not allow a probe the size of my multimeter in there. No way! Quote Link to comment Share on other sites More sharing options...
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