legacycentral bbs

I bought the car (91 legacy wagon, 5spd,awd, ej22) for $400 for my sister. The guy hit a deer doing 60 with it and it had been sitting since January '08. So i replaced the radiator,charcoal canister, lights hood,etc.

The first problem is everytime I start it, it idles up and down, between 500 and 2k. But if i rev it and hold the rpms at 2k for about 15 seconds and let off it'll idle normal.

Second problem is everytime the car drops under 1k rpms the oil light comes on. As long as the rpm's are over 1k the oil light stays off.

Any input/ideas would really help.

Thanks

for the oil light, try taking a wire brush to the metal tab connector on the oil pressure sensor (its under the alternator)

this cured my oil light problem. if it doesnt, your oil pump is shot or youre low on oil. for idle problem, im not sure. check your vac lines maybe?

The oil pump doesn't stop pumping oil. If your bypass was stuck, you would make no oil pressure at all.



The most common thing that happens is the oil pressure switch itself goes bad. I had this on my beater wagon. It's a $12 part.

Oil pressure is a function of engine RPM because the pump is turned by the crank via the timing belt. A good rule of thumb back in the day was that you wanted to see at least 10 psi for each 1k of RPM. So at 2k you wanted at least 20 PSI. Its also important to note that one cannot build oil pressure if the engine is not mechanically sound. A good amount of the pressure is build up at the crank bearings. Typically if you blow a bearing, you loose the ability to maintain oil pressure.

I would think that most oil pressure lights would go off if oil pressure was less then 10 psi because I would say that is the absolute minimum oil pressure you would want to be getting out of a running engine.

In this case, we know the sensor is at least partially working, because above 1k RPM, the sensor see's enough pressure to not set off the light. The problem could still be the result of a faulty or clogged sensory and I would replace that first since the part is so cheap.

If it is not the sensor then I would get an oil pressure gauge mounted to get an actual reading. If its low I would suspect the oil pump. If its not the pump, then that leaves a mechanical engine problem.

Subaru oil pumps are directly turned by the crankshaft, since it goes through the oil pump. They cannot stop pumping unless the screws come off the back cover plate, but you would definitely know if that happened. Some of the 11mm STi pumps have had a problem with the pressure relief valve sticking open, but that is a recent deal, and should not apply.

The oil pressure switch is designed to go off at less than 7psi on a subaru. Often times they crack and leak. Cheap and easy fix to replace them.


Mine oil came on at idle, and went away the instant I toutched the throttle. It slowly got worse over time, and only happened when warm. I finally got off my ass and took the alternator off to look at it, and sure enough it was cracked. I swapped one on from one of the other shortblocks I have laying around, and no more oil light.

funny, when i asked this question everyone said it was my pump. bastids.

either way, clean and reinstall the pressure sensor and see if it works if you want to save cash. worked for me, but for good measure i ganked a used one from the JY.

Alright Ill check the oil pressure switch/sensor first and see what happens.

And for the idle i was thinking it was a vacuum line but just wasnt sure where to start.


Thanks for all the info.

Is your ECU light on? Checking codes is a good place to start. It could be a vacuum line, it could also be a problem with your Idle air control valve or a dirty MAP sensor.

i'd say the oil light issue has been adressed check your oil, change the sensor, and if that doesnt fix it its probably a big deal.

as for the idle my 3 guesses are first a dirty mass air flow sensor. take the airbox off then the 2 tiny screws holding the sensor in to the round metal housing and very carefuly spray air intake or carb/combustion chamber cleaner over the 2 tiny wires, then let it air dry.

second would be your ecu coolant temp sensor not the one sending the signal to your dash, theyre separate sensors. sometimes if the sensor is off the computer gets confused and starts to add more fuel because it thinks the engine is cold but it isnt so this immediately causes the o2 sensor to signal the computer that its seeing too rich so it'll keep adding fuel and then taking away and then adding and taking away.

third i'd say a problem with your idle air control valve. sometimes if there is enough of a build up of gunk in the throttle bore it could cause it to hunt up and down so try cleaning out the throttle bore with the same stuff as the mass and maybe get a shop to hook up a scanner to see what the iac is doing.

it could possibly relate to a deteriorating throttle position sensor but not likely.

just my attempt at helping

-Alex

No More Oil Light! ..... replaced the Oil Pressure Sending unit, it was a $5 part at Napa.

thanks everyone!

good to hear! it always makes me happy when 5$ and a half hour are all it takes to fix a problem.

any idea about the roughness issue?
its really easy to clean out the mass air flow sensor so i'd say do that regardless because when i got my car doing just that cleared up a rough idle and a problem i had where when i touched the throttle just slightly the rpms would drop and the car would even stall sometimes. so i say everyone should do it! just use a cleaner thats safe for it and dont touch the tiny wires just spray them and let dry.

if that doesnt fix it change you ecu coolant temp sensor, its kinda tricky to get to but its probably a pretty cheap part like the oil pressure switch so its a worthwile investment.

-Alex

Yeah for sure I was really excited when the light stayed off!

I'll clean the MAF next and see what that does. If that fails I'll change the coolant temp senor.

The check engine light has been on and I finally got around to getting the codes.

Code: 42 - Idle switch

Code: 35 - Canister purge solenoid valve

Would any of those have to do with the idle?

and what exactly do those mean? My haynes manual sucks.

-Thanks

The canister purge solenoid can keep the CEL on. I'd suggest replacing it, and adjusting the idle switch

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