heres the story, did a 350 swap into 89 camaro rs that was equiped with 305 tbi. i deleted smog system, reused the same intake that the 305 had. vehicle ran great with 305.
now that the swap is done i had a irratic idle. reving from 650 to 1300 rpms and back down. when the engine came to normal operating temp about 220 the engine would run alittle better idled alot better but would eventually flood due to a bad coolant temp. sensor. i replace the sensor and the flooding stoped but the engine doesn't idle waf until it warms up. any suggestions will be greatly appreciated

 

Did you change the chip, fuel injectors, knock sensor & ESC module?
If you don't have a vacuum leak, I would suspect the computer's having a hard time dealing with the fuel requirements,if the 305 injectors and chip are still in place.
-Rich-

 

i've heard both stories that u can and can't use the stock 305 equipment when doing a swap, the 350 was a tbi 350 out of a 91 1500 pickup, if this case any suggestion of what chip and injectors to use for best performance, the system still is vats equiped.

 

Well, I can only speculate as to exactly what the problem is, but I've done the 305 TBI to 350 TBI swap on my 92 RS and since mine's a stick shift, it required a custom chip. Also, my cam's not stock. So I had a chip burned by Ed Wright (fastchip.com).
If you used the 350 injectors (#17112493) you should have plenty of fuel delivery capability, but the factory chip may not be able to compensate enough. An adjustable fuel pressure regulator will help with fine-tuning as well.
I had a similar idle problem at first, but it was due to a vacuum leak at the base of the throttle body (ported unit I bought from Turbo City wasn't flat). After removing it and milling it flat, my idle problems were gone.
If you disconnect the IAC motor (4 pin connector on passenger-side of throttle body), does the idle still vary?
If the IAC is all over the place "hunting" for a good idle, it's probably computer/chip related.If it still idles erratically without it plugged in, i'll bet you've got a vacuum leak that gets better when it's warm, (mine did).
Try the old "spraying choke cleaner" around the base of the throttle body when it's idling smoothest and see if it increases. If it does, you've found a leak.
-Rich-

 

I did that same motor swap on my '92 RS. I switched the chip, injectors, module, and Knock seosor, but I have an idle problem too. Mine idles at 1700 RPM. My car runs like crazy, but just has that idle prob.

Your problem sounds like vaccum or the chip theory.

Also, for the small price you pay for the module and knock sensor, you should do it. Detonation can KILL the motor, and that just might happen.