Closed loop runs like crap... open loop hauls... PLEASE HELP!!!

[ZekeTheFarmer]

Alright.... I've been having a problem with my 92 240sx for some time now. It was running alright, but it seemed to vapor lock if I ran it for awhile, shut it off, then started it back up. Then it started doing it all the time. Now it idles very rough, and under any conditions EXCEPT full throttle, just sputters down the road. Under full throttle, when the computer goes into open loop, it smooths out completely and hauls *** after 4k. As soon as I let off the gas, it runs pig rich and backfires like crazy.

I disconnected injectors and found that #4 wasn't pulsing, even though the harness was providing pulse. I replaced #4 and she ran much smoother, but idling sucked real bad. I put new seals on it when I put it in too.

I checked the coolant temp sensor, and it's just fine. Computer isn't throwing any codes. When I first got the car, it would seem to have this problem, but after a few revs, it would suddenly click and instantly go back to running perfectly. Now it won't stop doing it.

Any help/ideas would be greatly appreciated!

[Silvia007]

Clean the MAFS??