I have a 1995 Subaru Legacy wagon and I think my Throttle Position Sensor my be bad. For a couple of weeks when the car would idle it would flucuate between 700 and 1500 rpms not one or other but irradically. Then once the car was warm and I would pull up to a stop sign and sometimes the rpms would drop down to 500 or just below and of course the car was running a little rough.

Now the check engine light has come on. Bummer

I first checed the idle control valve and it was working properly. I would unplug it and the rpms dropped and plugged it back in and the rpms came back up. I would like help on how to test the Throttle Position Sensor. My book tells me to test the terminals for ohms resistance depending if the throttle is closed or open. Terminals 2 and 3 throttle closed 12 k-ohms and throttle open 5 k-ohms.

Terminals 1 and 2 throttle closed 0 ohms and throttle open 1 mega-ohm. I have tried this test and my ohms results did not match. I was reading a Chiltons repair manual and do not trust it. I would like to know more ways of testing it?

 

Thanks!

First of all go get the codes pulled at AutoZone to see what the Computer is seeing.

What do you mean by getting the codes pulled at AutoZone? Do they have diagnostic computers or code readers?

First of all go get the codes pulled at AutoZone to see what the Computer is seeing.

Yes. They will do it for free.

Well, I know Advance Auto parts will.

i thought only Autozone has scanners? advanced has them too?

 

Back OT (ON Topic), if you're showing a code you're wasting your time fiddling with anything until you find out what code is showing for the check engine light.

 

your car is completely different but BE ADVISED the FSM is DEAD WRONG for TPS adjustment on an XT6. don't bother trying it, you'll never get it to test by the spec's in the FSM because the FSM is BS. i'm not saying your car is like this, but check before you assume the TPS is bad. i wasted an assload of time trying to decipher this one night many moons ago.

I had the codes read and they were PO130 Front Oxygen Sensor circuit Malfunction and PO505 Idle control system malfunction. What should I do now?

 

McWalter

 

First of all go get the codes pulled at AutoZone to see what the Computer is seeing.

I had the codes read and they were PO130 Front Oxygen Sensor circuit Malfunction and PO505 Idle control system malfunction. What should I do now?

 

McWalter

 

i thought only Autozone has scanners? advanced has them too?

 

Back OT (ON Topic), if you're showing a code you're wasting your time fiddling with anything until you find out what code is showing for the check engine light.

 

your car is completely different but BE ADVISED the FSM is DEAD WRONG for TPS adjustment on an XT6. don't bother trying it, you'll never get it to test by the spec's in the FSM because the FSM is BS. i'm not saying your car is like this, but check before you assume the TPS is bad. i wasted an assload of time trying to decipher this one night many moons ago.

You didn't say how many miles you had but I have a 95MY 2.2 (132,000) that did the same thing, including random idle speeds and the O2 code. I reset the computer and dumped 2 bottles of injector cleaner in a fresh tank of gas, then 1 bottle for the next 2 tanks. Idle is back to normal and no CEL.

 

Might be worth a shot, it worked for me and this was after I finally got tired of the problem and took it to the dealship and had them check everything they could think of. They found no problems or an explanation of the cause that I managed to cure. I'm now considering Seafoam when the weather stays warmer to knock out any carbon in the top end.

i doubt its your TPG, but to find out hood up a DMM (digital Multi Meter) to the TPS, with the throttle plate closed it should read 0v and at wot (wide open throttle) it should read close to 5v.

 

if it goofs up in any time that you are SLOWLY opening the throttle, or spikes or anything like that, the TPS is bad.

 

but it sounds like your IAC (idle air controller) is bad.

 

Good Luck,

Shean

Idle Air Control. May be I am wrong, but at Idle, Subaru bypasses the Throttle Plate completely. Search this site on how to clean IAC.

Could he swap his front and rear o2 sensors, clear the cel and then see if the same code comes back?

You can test your TPS with a cheap wal-mart multimeter. Do an OHMs resistance test for each pin on the TPS and check it against specifications. Call local dealership and ask for TPS specs for your year/make/model.

Sounds like an inexpensive fix and I will try it! I was wondering what Seafoam is?

Oh yeah, I have 145,000 miles on my 1995 Subaru

Thanks!

 

You didn't say how many miles you had but I have a 95MY 2.2 (132,000) that did the same thing, including random idle speeds and the O2 code. I reset the computer and dumped 2 bottles of injector cleaner in a fresh tank of gas, then 1 bottle for the next 2 tanks. Idle is back to normal and no CEL.

 

Might be worth a shot, it worked for me and this was after I finally got tired of the problem and took it to the dealship and had them check everything they could think of. They found no problems or an explanation of the cause that I managed to cure. I'm now considering Seafoam when the weather stays warmer to knock out any carbon in the top end.

You didn't say how many miles you had but I have a 95MY 2.2 (132,000) that did the same thing, including random idle speeds and the O2 code. I reset the computer and dumped 2 bottles of injector cleaner in a fresh tank of gas, then 1 bottle for the next 2 tanks. Idle is back to normal and no CEL.

 

What kind of fuel injector cleaner did you use? There are just so many on the market, i don't know whats good and what works best. Is it really worth spending the mor money for the expensive ones?

Seconding the old unanswered question -- what kind of injector cleaner?

 

 

My 1988 SPFI (less than 300 miles on a rebuilt engine from CCRinc now) has what feels like a sticky mechanical gas pedal. I realize it has a 'throttle position sensor' instead of a mechanical linkage.

 

Feels like rust on a mechanical one -- basically when starting up in low gear, the car will buck/surge no matter how gentle I am with the accelerator.

 

If I floor the pedal, it'll .... pause ... hesitate ... vroOOOOOMMMM and then be very smooth.

 

Until the next time I try to use the pedal lightly.

 

I'm assuming it's probably a bad throttle position sensor.

 

And -- aha -- this morning, it gave me the appropriate 31 code for fifteen or twenty seconds on first starting it up.

 

Since I was already on the way to the mechanic to try to find the clunk it's developed when the wheel's turned full right, in the right front after they replaced the right front inner axle boot (sigh) last month -- they got it now.

 

But does this sound right, like the TPS is bad?

 

I also found the note elsewhere that it's easier to take a big file and knock a quarter inch off the air conditioner housing than to remove the whole mess o'stuff the manual requires to take off the TPS. But I doubt I can talk the mechanic into saving me any money.

 

Dagnabbit.