Bobs93Legacy

How much are they asking for them? If the price is right I'd take a couple.

Thanks for the offer. Mine is a 4-pin TPS, so I'm guessing the 3-pin version won't work.

That looks like some very useful info. When it says pin #1 to "body" does that mean pin #1 to ground - or to the metal of the throttle body - or is that one and the same thing (i.e. the throttle body is grounded to the rest of the vehicle).

Yeah, I'd think the rolled brass rivets would be the ones that have to be drilled out. FWIW there are two holes in the cover that line up exactly with those rolled brass rivets - and if you look down into the holes with a bright light you can see brass in the bottom of the holes. See attached picture

el_freddo - there are no melted tabs on the back side, but there are a couple of brass rivets (see attached photo). Maybe those are what he drilled out? I've also attached a shot of the tabs I mentioned earlier on the back end - opposite the end with the connector.

After viewing a couple of online videos about how to test a TPS on the vehicle, I decided, just for grins to use my VOM to check the pin-to-pin resistance across every combination of the 4 pins in the original TPS, since it is off the car and handy. For each pin combination I tested the resistance with the TPS turned full closed throttle to wide open throttle. If pin 1 is on the bottom and pin 4 is on the top when the TPS is mounted to the side of the throttle body, here are the measurements I got Pins Closed - WOT ______________________________ 1 – 4 measured 10.59k – infininty 1 – 3 measured 10.59k – 220 Ohms 1 – 2 measured 0 – infinity 2 – 4 measured 10.59k – infinity 2 – 3 measured 10.59k – 10.59k 3 – 4 measured 0 - infinity For combinations 1-4, 1-2, 2-4, and 3-4 that produced an infinity (open circuit) measurement at one end of the scale, the reading changed instantly from its initial value to infinity as soon as the TPS left the closed throttle position. For combination 1-3, the resistance measurement seemed to move across the range in a progressive and even fashion as the TPS moved from the closed to wide open throttle positions. For the pin 2-3 combination there was no change.at any point between the closed and fully open positions. I still need to perform the testing procedure with the TPS on the car, but I suspect that the progressive linear increase in resistance between pins 1 and 3 - which should result in a progressive linear increase in voltage across those two terminals when it is installed in the car, means that the TPS is OK. I really hope so - new ones are unobtanium, used replacements are around $100, and a reman is around $250! So I'm even more suspicious that the problem is in the plug or the wiring. Does that seem valid? Any other thoughts?

Well, unfortunately swapping the top of the airbox and MAF didn't do the trick. First thing I checked was to see if the CEL came on when I started it and it lit up as it should. Next I disconnected the battery for 30 minutes as suggested to clear the codes from the ECM. I then plugged the two black diagnostic connectors under the dash together and reconnected the battery and started it up. No change in symptoms (of course). I shut it off and then turned the key to RUN. The CEL started flashing. It appeared to flash a code 31. I say "appeared to" because I am unclear whether the CEL lights up and goes off before it starts flashing stored codes - or does it immediately start flashing codes without first lighting up to show it is working. If it starts flashing the codes immediately then the code is 31 - TPS sensor/sensor wiring If it lights up once (just to show it is working) and then starts flashing codes, then the code is 21 - Engine Coolant Temperature (ECT) sensor. I'm kind of doubtful that the ECT would cause the lack of throttle response that I'm seeing. If I'm wrong about that hopefully someone will correct me. So, I'm thinking that it is indeed Code 31 - indicating an issue with the TPS or wiring. However, since I have already swapped out the original TPS with one from my parts car, and nothing changed, I'm leaning towards it being an issue with the wiring/connector. While it is possible BOTH of the TPS units I tried are bad, it seems kind of unlikely. Per el_freddo's suggestion I tried to remove the cover of the original TPS, and didn't have much luck. The end opposite the connector seems to have two tabs that can be pried open with a little screwdriver, but the cover still doesn't want to come off. I tried working a screwdriver tip into the joint between the cover and steel base plate on the sides, but it doesn't seem to have any kind of tabs or notches that can be pried apart to "unlatch" and release the cover. I'm afraid of breaking it, especially since they seem to be such a rare part. So, next will be using my VOM to trace and check the wires in the TPS connector plug and make sure they aren't broken somewhere between the ECM and the TPS. I'm also open to any other comments or suggestions, as well as the question of whether the CEL should give one "preliminary" flash before it starts flashing the actual codes, and therefor whether the code it is flashing is actually a 31 - or is it a 21? Lastly, I'd appreciate any input anyone might have about whether a bad Engine Coolant Temperature sensor could cause the kind of issues I'm having. Basically I still have more questions than answers at this point 😜 P.S. I had it towed to the house using my AAA benefits. Since my membership renews at the end of the month and I hadn't had a tow yet this year, I had nothing to lose, and now it is home where I can work on it as I have time without making a trip across town.

Well, I'm back in town and will be taking another crack at getting it running on Thursday afternoon (it's over at a friends house on the other side of town right now). On your advice, I had him disconnect the battery so the codes will all be cleared by the time I get over there to try and get it running. At this point I'm thinking it isn't the TPS since I've already tried swapping one off my spare parts car and it made no real difference. I'm thinking that if the MAF is bad then it wouldn't throttle up properly because it wouldn't be correctly measuring the increased airflow - and therefore the ECU wouldn't supply the right amount of fuel to maintain the correct air/fuel ratio. Logically, that would match the symptoms I've seen so far. But if I'm wrong about that or missing something, please feel free to correct my troubleshooting process. So, based on that theory, today, I pulled the whole top of the airbox assembly (including the MAF) off my parts car to make it quick and easy to swap out the MAF. That will be my next step in trying to troubleshoot this issue. If swapping the top half of the airbox and MAF doesn't help, the next thing I'll try is to swap out the knock sensor (thanks for that suggestion el_freddo). I just watched a u-tube DIY video that showed me exactly where it is located and how to replace it. I'll pull the knock sensor off my parts car tomorrow and take it with me on Thursday. If swapping the MAF doesn't solve the problem then the knock sensor is next. Thanks for all the suggestions and advice guys! You've given me some really good pointers on what to check. The absolute worst-case scenario is that if I can't figure it out & fix it, I'll use my AAA membership to have it towed home where I can work on it at my leisure. Stay tuned - I'll post back to this thread with updates on my progress and what I find. Thanks again for all the helpful suggestions...

Thanks for clarifying that Imdew. I thought that disconnecting the battery for 30 minutes was what that meant, but it is very helpful to have that assumption confirmed. FWIW, I've never seen or heard of it taking anywhere near that long for a computer to reset when the power is disconnected. I'm guessing Subaru must have put some kind of capacitor-based memory backup in their ECUs for them to require such a long power-down-reset cycle. Most computers will reset in under a minute when disconnected from their power source.

el_freddo - thanks for the part number info. VERY helpful. A Google search for 22633AA060 pulls up several links - but unfortunately most of them say the part is "obsolete" or "unavailable". I was able to find a couple of places that sell that specific part. It seems that this particular TPS may have only been used a very limited number of 1993 Legacy models produced. As a result they are VERY expensive. Just my luck I guess 🙁 I'm still not 100% clear on what you previously referred to as the "30 minute battery dance" to clear the ECU codes. Can you tell me a little more about that? Sorry for asking what may seem like such basic newbie questions, but this is the first early 90's Subaru I've ever had to troubleshoot. Thanks for all your help and advice guys!

That's a helpful tip - thanks!

moosens - thanks for the info. Unfortunately, since mine was built before 03/94 (1993 model) it doesn't look like the one I come up with when I search on those part numbers. That part looks like it has a "tab" that engages a slot in the throttle body shaft. Mine has a round shaft that is flat on one side and the sensor has a hole shaped like the end of the shaft - it slips ONTO the shaft itself. Imdew - sorry I missed answering your question. It isn't showing a check engine light - but it is possible that the bulb could be burned out. FWIW, I found a video that shows there are two little black connector under the dash to the right of the steering column that can be plugged together and make the check engine light "blink" the codes. I haven't tried that yet because I'm out of town until the 15th. That will be my next step. Hopefully the CEL bulb isn't burned out!

Thanks Bennie. Just curious why I can't find a TPS listing on Autozone, Oreillys, Napaonline, eBay, or even Rockauto. Does Subaru use another name for it? Or is it a dealer-only item?

First, I found MAF sensors and MAP sensors on a couple of auto parts sites - but no throttle position sensor (TPS) - which made me think there isn't one. Does Subaru call it something else? Because there is definitely a sensor/rheostat on the shaft of the throttle body. So, I did some troubleshooting yesterday. Unplugged the MAF sensor (on airbox front corner of the passenger side of the engine compartment) and it died instantly Unplugged the MAP sensor (on center of firewall?) and it died instantly Unplugged the sensor on the throttle body (TPS?) and it kept running, but the throttle issue stayed the same. Plugged it back in and the throttle response issue seemed to go away - but only for a short time. I replaced that sensor with one I pulled off of a parts car I have, but the throttle response issue remained. Though I don't know that the replacement part was any good either. I used a pick to bend/tighten up the female connectors in the plug to the sensor on the throttle body, but that didn't seem to help either. I'm really stumped on this one. HEEEEEEELLLLLLP!

FWIW, I grew up working on vehicles that had carburetors and mechanical diaphragm pumps for fuel delivery, and a distributor with points & condensers for spark. This 93 Legacy was built when those types of mechanical systems were being replaced by computer controlled "engine management systems" - but before there was any kind of standardization (like OBDII). That makes diagnosis of this kind of issue REALLY challenging for an old-school guy like me. This sort of driveability problem isn't simple, like rebuilding the carb or resetting the points. BUT, at the same time it isn't a simple matter of connecting it to a diagnostic tool and letting the onboard computer tell you what is wrong either. SO, any help or advice the experts on this board can provide would be VERY much appreciated.