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?