Engine tries to die while driving, code 12 & 13 stored

Hello all,

Last week I got a CEL while driving my '89 Spirit, but didn't think anything of it because it didn't come back next time I started the car and seemed fine for a while. But now it happens every time I go somewhere, CEL and 12 & 13 stored in the SMEC. Sometimes the light will come on as I'm cruising down the road and I just keep driving with no issues, if it happens as I come to a stop the engine runs really rough and tries to stall. Last time it happened was on the way home from work today, I glanced at the wideband gauge and it was running stupidly lean (like 26:1) before it died. It's not fuel pressure related, pressure is steady at 45lbs.

Code 13 is the map sensor, so I pinched off the rubber hose going to it and the engine stalled like I would expect so I assume the problem isn't map related and it's only popping because the RPM's drop when this happens which causes map to rise as well.

Code 12 is sort of cryptic, but if the ECU were randomly losing power leading to a reset I could see that causing the issue I'm having. I did notice the voltage gauge reading a little lower than normal lately, but the battery is staying charged and terminal voltage stays solid at 13.3 volts no matter how many loads I turn on so I assume the regulator is doing its job. Only thing I changed so far is the auto shutdown relay, which didn't fix anything.

this is an FWDP socketed SMEC with my own tune in it, any ideas where to look next? It's my DD, I kinda have to get to work. lol

Code 13 is a MAP sensor code, but it's the vacuum related MAP code. You wouldn't be the first to solve a problem like this when you carefully inspect the vacuum lines the 3rd or 4th time. This is especially true if you haven't redone the vacuum lines and are using mostly stock components. They have pretty much disintegrated by now in most people's cars.

Vac lines have all been replaced and are not leaking, I have a manifold gauge tied into the same line and it's not showing anything anormal when this happens. I would think if a line were leaking it would run like a$$ all of the time, rather than having a hiccup and recovering.

Are you still using the baro read solenoid? If you are, try bypassing it and see if it goes away. I've had them get flaky on me and cause issues in the past.

Any idea if baro reads occur with the engine already running? My understanding of most ECM's is they take a reading just before the engine is cranked, storing the reading for speed density calculations. Only other thing I can think of is I read once that MAP sensors can sometimes get fouled by moisture, and to let them dry out inside the house overnight.

It does take readings while the car is running.

Thanks for that,

checked the read solenoid and cleaned it out with carb cleaner, it seems to work like it's supposed to and didn't seem blocked. Who knows though, maybe it was just dusty enough to cause a random problem. Time will tell. Anything else I ough to check in the meantime? 3-bar MAP sensors are pretty cheap, I could always replace it as a precaution.