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So my roommate has a 1999 Subaru outback (BG) 2.5L manual, lately it’s had a loss of performance and increased fuel economy. lately the car has started to just die while driving, no warning just stops dead low speed, high speed, on flat roads and worse on hills. the idle has started to stumble, the car starts all right and idles fine most of the time but occasionally the idle goes down below 500RPM and picks back up again and stays that way for awhile before stumbling again. there is no CEL (Check engine light) and for a while now i’ve noticed what sounds like a large exhaust leak around the exhaust manifold so i’m thinking it’s been building up back pressure and has cracked the manifolds or blown out the gaskets.
i took it for a test drive and i could give it the beans, shift though 1st to 5th full throttle at low speeds and let the revs run out (no more then 5k RPM) on uphill or down hill. it wasn’t till i had driven it for 20 minutes or more and took it to a back road and started going up a hill in 3rd or 4th with alittle bit of throttle that the car started to buck, and misbehave, i lowered my speed and put it in a lower gear and took it easy and it cleared its self up and then it was back to normal and i could romp on it again. (he had only told me about the cars engine suddenly stalling, not the bucking).
it’s almost the same car as Eric’s red BG Liberty/Legacy, and i plan on picking up a Vacuum gauge and seeing if there is an exhaust restriction as that’s what i think it is but i’ve heard a bunch of people having similar issues and there’s either nothing mentioned about a fix or what was wrong or there is the same issue but fixed by a dozen different things.
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Have you checked for codes just to see if there is any history or stored codes? Some of the more common problems on these are MAF sensor and A/F ratio problems. Fuel trims might be helpful to see if its leaning out or running too rich when the symptoms occur. Does it feel like the engine is misfiring or just sluggish.
it’s my roommates car as i said and i’m having a look at it now, i’m advising him to take it to somewhere with an OBDII Scanner and see if there are any codes. the car doesn’t run sluggish, he says it’s lost power but it’s almost as peppy as my 05 Lancer with the 4g69 MIVEC. when i drive it the other night it was an uphill and the car started to miss and stumble so i backed off and lowered my speed untill it cleared then it was fine again. today after replacing a vacuum line that was as hard as plastic, the car started fine and idled okay, i ran the vacuum gauge on the intake and the reading stayed steady so no blocked exhaust. took it out for another drive and for about 20-30min it drove flawlessly it reved freely and was nice to drive. i drove it back home and turned it off, i turned it back on though (few moments later while engine was still hot) and it immediately stumbled and stalled, started it again and the revs kept dropping down below idle so i turned it back off. really has me confused at how temperamental it is.
If nothing turns up when you get codes pulled, I might look at fuel pressure too. As suggested, the fuel trims might give you an indicator to a fuel pressure problem too. The pump might be ok on the cold starts but then craps out as it gets warmed up itself with normal running.
replaced the fuel filter and the fuel pump, the car seems to be idling a hell of allot better now and doesn’t just stall that i’ve noticed. though what i have noticed is that if i hold the RPM at 2000 there’s an intermittent Missfire and while driving the car bucks and surges and carries on. took it to a local mechanic and we couldn’t find the OBDII port on it anywhere under the dash. Right hand driver, Australian vehicle. 1999 BG outback 2.5L EJ25
Have you gotten any codes pulled yet? Don’t be afraid to look for them even if there isn’t a check engine light on. The PCM can store codes without turning the light on.
i can’t get the codes pulled because we can’t find the connector anywhere, there’s no OBDII or any other Subaru Diagnostic connector. i took it to a local mechanic and he couldn’t find any connector, i took it home and i dug around under the dash, pulled the panel off goggled the crap out of it. we cannot find the connector anywhere.
On the US models there is a door on the dash close the hood release not sure if there is one on the AU models but it might be worth a look to if it is there
Finally figured it out, ours doesn’t have the door or anything. what i did manage to figure out is theres two sets of plugs under the dash, two green two black. the green Male and female plug into eachother and it puts the cat into a test mode, all the fans cycle relays click all that. the black male and female are the read connectors. plugged them into eachother and turned the ignition on and the CEL started flashing, Bingo. got the codes down
in this order
First: 33, Abnormal voltage input entered from vehicle speed sensor.
Second: 12, Abnormal signal emitted from starter switch.
Third: 23, Abnormal voltage input entered from air flow sensor.33 was fixed but i guess the code never got cleared
12 doesn’t seem to affect it as the car starts fine
23 is concerning but last night i unplugged the MAF and tried to see if it would start and run (it didn’t) in a troubleshooting process so i think that might be where that code came from. i’ve disconnected the battery and i’m going to leave it over night to see if the codes will clear, if not there’s another procedure i can use to clear them (i hope). take it for a drive once the codes clear, let it muck up until it throws another code and see what it gives me. if it throws another 23 then i’m going to look at testing/replacing the MAF sensor and throw a set of plugs/leads on it as well.
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