My 94 LS400 wouldn't start, but I wasn't immediately concerned because it's a project. I rebuilt my ECU along with my 91's. Still wouldn't start, so I checked the engine code and got a 12. I pulled the rotors, caps, and wires from my 91 and stuck them on it. I needed a running vehicle, but that's another story. The 94 fires right up on a test, so I button her up give another start. Now it's idling rough and stalling out. I unplug the MAF and we're GtG. I tested the 91s MAF and got the same result. I'm driving around like that for now, because I haven't much choice.

Any advice outside of "buy a new MAF?" Because I put another in from a different vehicle and it didn't change. Not really interested in buying something that isn't actually the problem. Is there any other issue that could be causing this?

 

I would check the connector and it's wiring before dumping money on a replacement MAF. Grab a multimeter, a manual (or maybe someone here can provide the steps), and start testing.

 

Well, it was an extra easy fix. Thanks to my local Toyota dealer for point it out. In my hurry to button up my junkyard tune, I didn't properly line up the rubber collar between the intake and the MAF housing.

This leads me to 2 conclusions:
1) I need a garage or other workspace.
2) I am a blind fool.