'91 legacy idles, but thats about it...

hi all, brand new to this forum, so please be gentle... anyways, my '91 legacy is now to the point where it will pretty much only idle. whatever prolem it is has been progressive cause i had been driving it regularly, and was noticing power loss for a while. I finally called it quits after an 80yr old woman passed me on a double yellow while giving me the finger. when I open the throttle it just bogs down and almost stalls, i can get it to rev if i give the throttle cpr like littlle blips, but thats it. when i do get it off idle it will rev up just fine, just getting off idle is the problem. Im guessing its a lean condition, fuel pressure seems to be fine, although I havnt put a gauge on it. the cats are no longer a question (dont ask). I cleaned the IAC passages, and checked thoroughly for vacuum leaks, and found none, or at least no large ones. had a mechanic buddy check it out, he told me to replace the airflow meter(but did no diagnostics, just guessed). I dont like to just throw parts at anything, especially expensive ones. I really want to save my subi, but I'm just baffled, anyone have any clues? any input would be greaty appreciated.

If you suspect the MAF to be the culprit you can try unplugging it and see if the problem stays the same or gets worse. If the problem stays the same the MAF is probably the issue. Usually the MAF will throw a code if it fails. Try the same thing with the TPS sensor. If you haven't already, try removing the IAC completely and giving it a good cleaning with some starting fluid.

 

Is the vehicle up-to-date on maintenance? Spark plugs and wires mostly. Fuel filter could also be gunked up.

check the fuel pump while your at it.

thanks, plugs/wires are relatively recent, and in pretty good shape. fuel filter is new tried unplugging MAF, stalls imediately. unplugged tps, no change, not sure what its supposed to do when tps is unplugged. i need to actualy check fuel press., but i know there is plenty of pressure, and volume just by letting it run w an open line. i have also cleaned IAC and passages, but did not try bypassing it. the engine light has been on for years, the lady before me put a piece of tape over it. wish i had a scanner to read codes, maybe i could barrow one. thanks for the advice, i'll keep postin with what i find out

You don't need a scanner to pull the codes out of this car. Even if you had one its not compatible since its OBDI. The scanners you can buy at AutoZone/Wal-Mart are for OBDII cars from 1995-1996 and later.

 

To pull the codes follow the directions at...

http://legacycentral.org/library/literature/codes.htm

 

In neutral with the TPS unplugged the engine should hesitate and bog down when you give it throttle. It should hesitate and stumble for a moment and then begin revving shortly after. Throttle response will be almost non-existent and the check engine light will stay on. If the car acts like this regardless of what you do to the TPS then you've found the problem. I'd start with the TPS and see if that gets you anywhere. A junkyard TPS would be a good place to start.

that sounds like it makes perfect sense, thank you, I'll try some local boneyards for a tps and see what I come up with. hopefully thats the ticket

does anyone know the correct procedure for testing this type of tps?

i opened up the tps and foind that the small electric board was broken in two places. local junkyards want like 150, bit i ordered a complete throttle body assy. from ebay for 25. just waitin now

awesome, good to hear.

Well here is a video of what it is doing after the new/old TPS. I checked the ohms of the throttle body I just received and matched it when I installed the new/old one on the car. Below is a video of how the car acts.

 

[ame=http://www.youtube.com/watch?v=hpLgH0f06WA]YouTube - 002.MOV[/ame]

I did change the TPS on an engine (actually a newer one, and it was the sensor for the TGV) but what I realized was that the sensor was mounted with pre-tension, so that *may* be the problem.

 

The fact that it dies on you with the old sensor idling seems to be that it runs too rich, which on the other hand gives you great engine response.

 

What you can try is to have the new sensor removed and use a screwdriver to manually set a position, then get a feel for the engine response at different positions of the sensor. That may actually give you a clue too if it's working as it should or if that sensor is bad too.

It will actually idle with the old sensor if you give it a few seconds to clear up, but as soon as i give it any throttle it will rev up just fine, and run realy well, just wont return to idle. I'll play with the new sensor and see what I come up with.

The new/old sensor definately makes a difference if I rotate it manually. If I get it set at a certain spot the car will run ok. not sure whats next, any help would be great, I realy want to get er goin again.

IAC maybe???

It seems to me that the positioning of the throttle sensor on the shaft may be the culprit. See if it can be mounted in more than one setting - like with some pre-tension. The operating angle of the sensor is normally larger than the operating angle of the throttle which has an angle of about 90 degrees. Most potentiometers have a larger span, but it varies, but with an easy hand and a screwdriver you can check what you actually can work with.

 

How does the throttle axle and sensor connection look like? Maybe you should post a photo of each because it's sometimes easier to talk about it when you have a picture to refer to.

 

And if you got an used sensor it may not have been in best condition either, so maybe you should look into getting a brand new sensor.

 

Check this article about TPS too: http://www.automedia.com/Throttle_Position_Sensor_Adjustment/ccr20040701ts/1

 

And there is one article over at NASIOC on this theme too: http://forums.nasioc.com/forums/showthread.php?t=1803797

 

Since it depends on model year and also engine type which throttle position sensor you have it's not easy to know exactly which one you have.

 

Attached are three different versions that I have found related to Subaru, but your may be yet another. Last one doesn't seem to be likely for your car, because that's what I found on a '06 STi.

I have the sensor pictured in the middle. I wish I could understand that japanese stuff a little better, it seems like great info. I took ohm reading from the used throttle body i got ( came from a running car) - 10.0 ohms at idle 2.1 ohms at wide open throttle. used TPS had white paint on the screws, sensor, and th. body marking its position( my car also had this paint) indicating that it had not been tampered with. I initially set the sensor to these specs when I installed it, made a little difference, but not enough. I tried "adjusting" it, which made a difference initially, but after a few seconds it returned to running poorly. I tried removing it from the th. body and rotating it with a screwdriver, could get it to a point where it would run o.k, but not return to idle. seems like the TPS is working properly, but its always possible that its no good. new ones are pretty pricey. I sort of think it has a vacuum leak, causing a lean condition, and "adjusting" the TPS richens the mixture, just a guess though. could the IAC cause a vacuum leak if its not working properly? thank you very much for the help, I wish I could buy you a few beers or something...

If you still have unreliable results it can be a bad pressure sensor or a bad hose.

 

But if the engine idles first, then after you have revved it a bit it no longer idles it seems to me that it might be a pressure sensor that's causing trouble. That because when you lift the throttle after revving you will momentarily get a lower pressure than normal idle and during that moment the ECU cuts fuel. If the pressure sensor sticks for a moment the engine may end up starved.

I checked the TPS voltage, its almost pefectly within spec. spec is 4.7 closed, 1.6 open, I have 4.68 closed and about 1.55 open, so I think thats close enough. any chance a bad IAC could cause this? I unplugged the battery for like 2 days, and the check engine light never went out. Im gona try n get some codes. the car will return to idle with the tps installed in the correct position, just wont rev, and no power. I checked he MAF, about 1.2v at idle, and could get it to a maximum of about 3.2v with no load. that sound normal? what's the pressur sensor, and where is it? is it like a MAP sensor?

what's the pressur sensor, and where is it? is it like a MAP sensor?

 

It's the MAP sensor I was thinking of. If it doesn't correctly detect the changes in manifold pressure when you change the throttle position then the ECU will get confused.

 

And since you have a CEL even after an attempted reset it's definitely a good idea to read the codes. See the sticky at the top of this section.

 

The MAF, MAP and TPS works in conjunction to try to get the best mixture for the engine. Some cars do have an atmospheric pressure sensor too, but that sensor is usually not of great concern. A bad O2 sensor can also mess up the results but disconnecting it should make the ECU go into a more conservative mode.

 

I'm not sure if your car has a knock sensor, but even that can actually confuse the engine if it says that the engine is knocking even if it isn't. And so will a bad temperature sensor.

 

One other thing is to check for leaks. A can of brake cleaner can actually be used since if it's sprayed on a suspect location then it will get sucked in and temporarily change how the engine idles. But use only small doses since it's flammable.

 

In another thread there was someone that resolved an idle problem with adjusting the valve clearance. That can also be something to look at. (Unless you have hydraulic lifters in which case it's not something to consider)

 

A clean coil pack and ignition cables are of course a key issue. Bad coil, ignition cable or ignition module are also factors that can produce strange results.

I got some codes, however, none of them seem to help. first, 33, which is speed sensor, car was not moving when this code came up, then 35, which is canister purge solenoid, seems to not open as i have found no vacuum to the charcoal canister(thought if it was open all the time it would be like a vacuum leak), next, 51, which is nuetral switch, next 52, which is parking switch. I dont think any of these indicate what is causing my problem, but maybe I'm wrong. any thoughts??

jst got a knock sensor code that I didnt get before. could actually be doing its job, the thing runs so bad sometimes it may have been knocking around idle. im getting realy frustrated with this thing, I am temped to try the 12 gauge solution....but i like it too much for that....

I think it's a bit too soon to give up on it, especially with all the Codes it has and you not fixing them yet

i am new to these cars as well but the code 51 , wouldn't that prevent it from starting at all or just mean it will start in any gear?

This car is RHD, the lady I got it from bought it new to deliver mail. after about a year the trans. went bad, it was covered under warrenty, but the dealer told her that because it was RHD it wouldnt work just right, that the chk engine light would always be on and she would have to push a button on the console to get it out of park. It has been that way since I got it last year. I am guessing that is the cause of the park and neutral codes, and because it doesn't "know" that it is in park it throws the speed sensor code. the purge valve seems to be completely inoperable, I thought it may have been causing a vacuum leak, but it doesn't open. I can only guess that I'm chasing some gremlin that wont set a code. I'm not realy sure what to do next, and realy appreciate you guys helping me with this, I love this car and am determined to fix it. I'm lookng into a parts car so I can just start swapping stuff. does anyone know anything about RHD models? is the trans that different? what else is different?