eword

Ok... watched video on dumping sea foam into IAC valve hose, still in place on motor, to clean. Did, sounded better, but idle still surging especially when under load.. fan, AC, lights..... but WTF... there is an adjustment possible on IAC valve! So I simply opened the valve a few degrees until the idle smoothed out under load. It seems to idle a tiny bit high under a no load condition, I might adjust after this settles in for a bit....... ANYBODY KNOWS WHY THIS ISNT A GOOD IDEA, please let me know! I don’t want to over heat motor with too lean mixture, or whatever else I’m about to mess up! so far though, the feeling of another subie conquered is FANTASTIC! Thanks you all for your advice as I stumbled through this. SUBARU!

Iacv is also suspect. Throws no codes, and half of my research on it says easy to clean, keep extra gasket handy, half says DONT EVEN TOUCH! I’d love to see it clean and verify function...

I fully agree with the rich mix, no codes for injectors, did ohm test all ok, mechanic had nothing show up on diagnostic computer for injectors..... brb

I think you recommended that, I’ve done it, no gas in line, no gas dripping out unplugged, BUT when I disconnect that, or ANY vacuum line, the idle evens out. the mechanic didn’t believe when this happened at shop this morning. But when I plug fuel pressure back in, or any other line, motor goes to extremely low idle then directly to surge...

I’m at the shop, they have confirmed all my tests for sensors, including MAF being within specs, also cannot find vacuum leak, are pretty confident an exhaust leak wouldn’t cause this (I’m probably going to check this later on cool exhaust with soap water), and are also baffled that creating a vacuum leak evens out idle, the shop owner walked away at that point... I’m trying to find out if the computer is shot, they said they have no test for ECM(?) Any ideas? in the meantime, I’m trying to reset computer by disconnecting battery, and try relearn.... thanks all. Hope to close this thread...

I have absolutely considered leaky injectors. There is no code being generated for individual cylinder so I would have to assume they all leak uniformly, though it doesn’t rough idle, it is a surging. Creating vacuum leak on either side of intake manifold smooths out idle. This also suggests to me it is a uniform issue with all injectors, if this is the case. I’m not wanting to risk breakage by removing them. Anyway to test this theory with injectors in place?

That’s what I’m shooting for. P0100 MAF is likely a vacuum leak, having visually inspected connector and observing proper voltage at idle and uniform increase with opening of throttle plate. Oddly enough, P0133, as I’ve just replaced O2, is also likely a vacuum leak or bad MAF which has been tested, and likely also a vacuum leak. so when I disconnect ANY vacuum from throttle body the idle smooths right out. Disconnecting the fuel pressure regulator smooths out idle until you plug hose going to TB, and closing that “vacuum leak” , and it goes right back to surging idle. Leaving fuel pressure regulator branch of vacuum connected, but disconnecting down stream switch also smooths out idle.. unless you plug the vacuum line, again surging idle. disconnecting the vent tube running from driver’s side head to air intake, after the MAF, will even out idle. Disconnecting brake vacuum line smooths out idle but idles high. I can partially plug fitting at intake manifold and drop RPM to a smooth idle. so, I’m trying to fix a vacuum leak when creating a vacuum leak seems to work. Is it just a rich fuel mixture that the unmetered air is helping to burn up? Why so rich? MAF and back to a vacuum leak that I kind-a want? everything I read and from past subie experience tells me p0100 isn’t about a bad MAF... which I tested... id love to hear ideas for tests, I don’t have the Bluetooth reader.. just voltmeter.....

Thanks, MontanaTom! I’ll definitely check this out!

Going back to test codes......

Changed 02. Nothing changed. Rescanned codes, got p0100, p0133pd mil on, monitrs catlyst 02 snsr O2 htr went to test MAF,, voltage too low to start test. test and replaced battery, test MAF, tested ok. drove great! For 20 minutes... Now back to same surging idle, seems like brakes are partly engaged? Doesn’t roll, clutch in, freely.....

My bad. I am wrong about the O2.... also dumb, as it was setting codes and telling me....... going to replace now. ill get my dunce cap and let you know........

If I disconnect booster hose, or PCV hose, and partially plug fitting at throttle body with thumb, allowing unmetered air, it idles smooth as silk. Thinking the air filter was clogged, I removed it, no change. Disconnecting MAF will stall motor, but on restarting, surging idle remains, slightly less RPM. When plugging MAF back in, RPMs pick back up, surging idle remains. Am I wrong in thinking bad O2 will send a consistent bad/ default signal and not cause surging idle?

This torque app? It says it’s a payment calculator...

Show up as a misfire in the affected cylinder as a code?

I disconnected the MAF and drove around. It runs rough, but still has the stutter thing going on. wouldnt a cracked valve seat or head gasket throw a code somewhere?

Also have cleaned upper throttle body and throttle plate..

I’ll check that hose. I’ll see if I can test these other components. Might be bad but not storing code?

It seems coil, injectors, sensors and stuff that throws a code, I’m back-burnering... evrything i replaced, except probably the fuel pump, needed to be replaced anyway. It was coding for MAF until I cleaned it. It’s not coming up anymore...

Wouldn’t those be setting codes, though? I was going to clean the IAC, but am finding conflicting advice on it online. Some show how to do it and have gasket handy, some are adamantly NO WAY, dealer only..........

Hey, e, you getting sick of fixing these old subies? e: nope but more info...... when this condition is NOT happening, you can balence a marble on the stick shift. Smooth as silk. Plenty of power and hopes for another 80,000..........

Just bought 96 legacy,173,000 miles, had a few things wrong, setting codes. Ran solid and smooth until it starts cutting out at random RPM/ load... Will still run and idle smooth, until it decides to start cutting out, then followed by uniform surging at idle. Doesn’t want to die, just Erving at idle.Replaced knock sensor and PCV, cleaned MAF, new plugs/wires/ fuel filter and pump. Seafoamed fuel and throttle body, to try to rule out all injectors being grimy. So when this condition is set, and irratic idle is happening, I can rapidly press the break pedal, and idle will smooth out. So I tested booster and booster check valve, and they seem to be in order as far as check valve operates in one way flow and booster checks with pressing pedal during engine running/off pressures on pedal and sinking when engine is turned on.... Was suspecting vacuum leak anyway, and thought booster diaphragm was ruptured because when pumping breaks smoothed our idle. But can’t confirm bad booster. Last codes after the replaced parts are 0100 and 0505, and catalyst, lean fuel, and O2.... anyone like the looks of this?

i recently purchased a 97 legacy outback for my daughter and discovered the radiator fan doesn't turn on. in stop and go trafic it will get close to over heating. but in the morning it takes forever to warm up. i expect to replace/ install a thermostat, but where is the fan relay? i should see why the fan does not turn on. right? check relay, then sensor? and isn't there 2 coolant temp sensors? it runs great and gets decent gas milage... thanks

hey all and thanks for your info. did check power to fuel pump. it was there. remembered soobie kyle's advice to hit the tank(he said with 2x4) to break up sediment(?). i did, but with 28 oz hammer. it worked!!! pump is operational for now. seems like i would have checked the pump a while ago if the bizzarre codes didn't distract me. off to get pump and filter. maybe betty lives again:) thank you all again!

OK......ya. checked for fuel before the filter and nada. got up under the dash to check relay. there is a brown, green, and white plug each holding relays. all info i have seen says green is fuel pump. but jumping the green plug turns on a fan. so i am double checking which plug is the fuel pump relay before i start frying stuff..... the green has 4 prongs, the brown has 6, i have not disconnected the white but it is the same round metal relay that is on the green plug. and either way no fuel before the filter

it's been low of -20. haven't been too eager to check the filter...