SubyDriver

I ended up changing a lot more easily sourced cheap parts on this but the thing that fixed it after a fresh oil change and flush was running seafoam (or something very similar) through the intake manifold!

Yes, they have all been replaced. I don't have a way of checking the fuel pressure, but I have a new fuel pump on hand that I need to install.

Changed the knock sensor (it had a split in the plastic), no difference. New MAF too, same issue. Took out the cam sensor too and gave it a good clean, no improvement yet. The car bogs the first time you give it a bit in gear (auto transmission), then even when you pull over it will struggle, if you keep driving bogged it will eventually stall and will start up shortly after, sitting it there for a few minutes will help it clear and then it's fine for the rest of the day. I can provide any more info if anyone thinks they have something I can try/look at.

The crankshaft pulley is good. Today it stalled for the first time when running rough because I was turning off a main road while it was bogged down and the power steering pump had too much of a demand on the engine... might need a replacement Subaru soon until I work this one out, it's becoming too unreliable at the moment. After stalling it started right up again and the issue was gone for the rest of the trip (still thinking it's a stuck valve lifter). Edit: New fuel pump on the way now just to rule that out.

Replaced the MAF, no improvement. I thought I'd might add, I tried a few things today when it started to bog (happens every day now so I'm used to it), it is actually rough even when put to neutral and revved hard, until it passes say 3-4K RPM. I've been reading around and some are saying that a common thing with these EJ22's is that a lifter will get sticky: http://www.ultimatesubaru.org/forum/topic/143243-1991-subaru-liberty-loses-power-under-load/ I've put in some new oil mixed with Marvel Mystery Oil at this point and I'm hoping for the best (no improvement so far). Checked error codes, nothing has ever come up on the CEL (light is working).

No leaks I could see, even at 3-4K RPM. I've ordered a new MAF through eBay, will report back when it gets here. Is the hose going to the IACV or PCV supposed to have a clamp on the PCV/IACV? Mine don't seem to have any and I'm wondering if it could be losing enough air from there.

Thanks for the tip, no CEL, but I will see if it has any old codes on it. I could grab a new MAF (OEM) for about $70 Will check for vac hose leaks tonight and report back.

My '93 Legacy/Liberty EJ22 2.2L AWD Auto seems to have a problem since about a month ago where it will start to run rough and have no power when going over 40mph (60km/h). If you shift it into neutral when it is having its hissy fit and rev it, it doesn't clear up. It only clears up after driving rough for about another 30 seconds or less under that speed and when stopped, revving it at around 2000RPM. The car doesn't stall completely at all, just runs real rough. I've heard it running on 3 cylinders and this doesn't sound the same, nor are there any violent sounds coming from the engine, just sounds like the engine is unbalanced or deprived of air or fuel or running rich. I've been reading around a lot about similar issues, and whilst I haven't tried changing everything that everyone else has, I was hoping someone might have a clue what could be a likely culprit or how to test for it. So far what I've done in an attempt to fix it but the problem is still consistently there: Changed PCV valve Cleaned Idle Air Control Valve Cleaned CAM sensor New MAF sensor New NGK OEM spark plugs New NGK Ignition wires New Air Filter New Fuel Filter New Knock Sensor Checked compression, it was good I should mention that the next thing I'm looking at is the fuel pump - am I on the right track here? The fuel guage has never read right since I bought the car 5 years ago and now it seems to have gotten worse, I don't have the means to check for fuel pressure though so I might just replace the entire fuel pump assembly.