SuspiciousPizza

@el_freddo I regret to say that I gave you some misinformation. O2 sensors WERE standard equipment on SPFI models. The Cali-spec used a 3-pin connector and the federal emissions (all the other states) used a 1-pin connector. I got confused since I bought my GL with an exhaust system without an O2 sensor bung. My guess is that at some point someone put a carb exhaust on the car as these didn't always have O2 sensors. Now I need to get an O2 sensor on my car. Which means welding up a new cat and splicing the wiring in that was removed. Hopefully now the car will get out of open-loop and I'll actually see above 22mpg.

There's been a new development. My ECU threw a code 32 for the O2 sensor. Best I can tell the car never came with one. I have swapped the ECU that came in the car for a different one. Perhaps the donor car came with an O2 sensor. But I've been driving with this ECU for months and it only now popped up the code. I'll swap back to my old ECU and see if that makes a difference. If not I'll swap in my Cali-spec cat I have and throw in an O2 sensor. It'd help my gas mileage - plus save the planet and all that. :]

For any of those interested Rockauto has 4 NEW SPFI injectors in stock under an '86 GL. They're $400 USD. That's a very low price compared to some eBay sellers.

I've had a wire break inside the engine harness to the IAC before. I've also had several connectors have poor terminal connection. Then again, I would typically get a CEL but not all the time. Since you have no hard starts I don't suspect a wiring issue with the IAC. The fact that you've swapped a majority of the typical suspect components and it still acts the same leads me to think an intermittent connection somewhere.

Have you checked the values and calibration of the TPS? I'm not as familiar with the autos as I am with the manuals. Isn't there a drop down circuit that senses when you go in gear and it'll drop the idle?

Solved - hopefully It was my EGR solenoid. It had an intermittent connection at the connector which was in turn messing with my vacuum. I'll keep an eye on it but the CEL that was intermittent was throwing a code 34. I'll also keep an eye on the connection to the IACV. :]

I'm sure with enough time they are serviceable. I'm not sure what the internals of the IAC actuator look like, it's definitely not meant to be taken apart. The entire valve is a part. You couldn't buy just the actuator even when they were available new. My guess is I'd "just" need to get a coil rewound for it. Something theoretically simple that in practice will prove to be anything but. The actuator I replaced tested okay. But I only tested it cold. The resistance changes as the coil heats up and maybe it was only out of spec when it warmed up? I'll be honest the only reason I was using that actuator was because it tested okay (so I thought) and it was the best looking. I was putting lipstick on a pig but it's still nice to see shiny parts on an old vehicle. :]

Now the CEL comes and goes every now and then. I'm guessing it's an intermittent connection. I'll have to pull the engine harness and check it. If it's not that then I'll have to check the body harness and the connections. Wouldn't hurt to check my grounds too. :]

It was my IAC valve. On my way home from work I finally got a CEL. Pulled the code and it was a code 34 for the IACV. I replaced the "solenoid" (turns out it's actually a bimetallic actuator that uses a heating coil) and it idles like a dream. Smooth as silk and the vacuum is rock steady, no excessive vacuum flutter on start up. :]

I did not get around to messing with the IAC. I was helping a few friends with their cars. What about the idle adjustment? Maybe my idle is set too low and the computer has to overcompensate. Does anyone have any pointers on how to adjust the idle on an EA82 SPFI setup? Do I have to connect the test connector(s)? Disconnect the IAC? I only have the MPFI idle adjustment in my FSM. This throttle body is a junkyard unit. So the chances of the idle adjustment screw being off are high. :]

I bought the injector and once I got it I compared it side-by-side with a Loyale injector. They're the exact same. I vacuum sealed the injectors with desiccant packets. Hopefully they'll last until I need them. I've heard it's the moisture that'll corrode the coils and kill them. Are you asking about that weird horseshoe gasket? For installation I use a few dabs of silicone grease to hold the gasket into the throttle body then quickly flip the throttle body onto the intake. There's Walker brand throttle body gasket kits, I'd recommend those. You get every seal you'd need for a throttle body rebuild. I'd recommend a coolant system pressure test after you install a new gasket. I've learned my lesson on that one the hard way. :]

I have not yet gotten around to messing with the IAC valve. I'll be doing some work on the car this weekend so I'll get to it then. The previous owner had spliced in some spade connectors on the IAC valve so the OEM connector was removed. Perhaps the valve was a junkyard/used unit that had the wires cut. Is it possible I just have the polarity flipped on the IAC and that's causing my issues? Will reversing to polarity damage anything? Perhaps the IAC solenoid. That mechanical portion of the valve was ultrasonic cleaned. Unless 3000 miles gummed up the valve that bad, I doubt it's a sticky valve. The issue is sporadic. Leading to me believe it's electrical. :]

I've been searching for a new SPFI injector to have on hand when the the pearly gates come calling for my limited stock of used injectors. MPFI injectors are a dime a dozen but new SPFI injectors are more difficult to track down. The only actual new parts I can find are compatible with the Subaru P/N 16637AA000. However this only seems to be compatible with 1986 and maybe 1987 models. My car is an '89 model which calls for the P/N 16637AA010. Is there really any difference between the two? It doesn't list 16637AA010 as a supersession part number. But I'd have a hard time believing that Subaru would have one injector only work with a 1-2 year model range. That doesn't sound cost effective. Why would they change the injector? Different flow rate? Updated spray pattern? Maybe a different throttle body casting? The latter seems very cost ineffective. New molds, tooling, jigs, etc. The kicker is that 16637AA010 shows it's compatible through the entire SPFI production ('86-'94 here in the States). :]

I'll check the IAC tonight. It's right out front and easy to access. If it's not carboned up I'll see if there's a resistance test or something I can do in the FSM. I have a few spares kicking around I could try if it comes to that. Also I did do a factory PCV reroute. I know the PCV was definitely sucking oil before I did this. I lost about 1/3 quart of oil over about 1300-1500 miles. I've checked my oil level recently (about 1500 miles since the reroute) and I haven't noticed any obvious loss of oil after doing the reroute. Then again my oil pump leaks so I'm unsure how much of the aforementioned oil loss was due to the oil pump leaks vs the PCV sucking oil. And my vacuum does begin to ever so slightly flutter above 3.5k-ish RPM. Less than 1inHg fluctuation but if you're looking for it, it is noticable.

I'd sure hope it's not the alternator. I swapped in a new one maybe a year and a half ago. The car has always had a voltage flutter and differing fuel pump whine with the turn signals. After I did some electrical work it has gotten better and now drops approximately 1 volt with the turn signals whereas before it was maybe 3 volts or so. I can always check the alternator terminal connections and belt tension. It doesn't sound like the belts are slipping (I'm running both belts in the same pattern since I deleted my AC). PCV valve is a new OEM part I added when doing a full refurb of the engine. I tightened it with a flange wrench too and while I didn't torque it, it definitely felt tight. Sealing the threads would be an easy thing to do. The engine I have in the car now was sitting for a few decades so I do suspect one or more of the valve springs are weak from the valves sitting open for so long. I didn't replace the springs because I couldn't find a full set of inner and outer springs. I'm still in need of outers, I have a full set of inners. Perhaps the springs just don't respond well to rapid changes in RPM? Valves get a little float? My vacuum on cold start is typically 15inHg then as the engine idles for a minute or two it'll creep up to 20inHg while staying at the same RPM (set to 1500 when cold). If the engine is REALLY cold my cold start vacuum is typically in the 12-15inHg range and the creep to 20inHg may take a little longer.