Bought a 92 rs like 5 years ago, as far as I know it was a stock 305 with eddy headers (had the AIR system comming from the headers was not hooked up) and a small crower cam and... it ran fine other than I'd have to double foot it (gas and brake to keep the RPM's up while I shifted out of park otherwise it'd die). Once in gear ran flawlessly... Now that bit of info is relevant because now I have another stock unmolested 92 rs 305. I got bored waiting for my 383 to get finished so I started messing with the engine.

Took the headers and cut the air lines off the top and welded the holes shut. Installed the headers and modified the stock Y pipe to fit. The exhaust is not hooked up but dumps down right where the cat was. I pulled all the AIR crap off the car (lines, air pump, etc). Using one of those crappy dress up air cleaner assemblies that doesn't utilize the stock air cleaner box so the only thing installed on it is the IAT sensor.

Now here's where I'm at and don't know what to do next...

1) It sounds like a lean missfire/running lean as the exhaust seems to flutter.

2) the vac line that was hooked up to the thermac (or whatever it's called) when capped seems to make the engine stumble more than when I leave it off and it raises the RPM and seems to run/idle a bit better

3) Has a code 23 (manifold air temperature (mat) sensor or circuit (1990 and earlier models) 23- intake air temperature (iat) sensor circuit (fuel-injected models)

4) Seems to be running in open loop which would lead me to believe it should be dumping fuel not running lean.

I believe that's all I got unless i think of something later.

Need some input/direction. What do I do? What's my next move?

Thanks.

 

Any ideas? Just doesn't seem to run right... Not sure where to start looking for the problem.