I have tore the intake off my 305 tpi to replace all gaskets. It still idles high. but does it differently. Now it will shoot up to about 3k and then slowly die to about 1500. Cold or hot. New iac and tps adjusted. Now i cannot adjust the iac because the engine will not idle. when i do the steps and start the engine. It will run for about 3 secs and then die. I can adjust the idle and it will idle about 1k but jumps up to 1500 and back down. It was a auto car now with a manual. Could my fuel pressure be too low?

 

I would first check for vacuum leaks.

 

already have...nothing. But i did finally get it to idle back down. I reset the ecm and the iac again. closed my exhaust cut out. I do have a crack in my y-pipe though. It still does idle smooth. Will jump up and down between 500 and 1500.

 

okay i think i finally figured it out. The fuel reg. was plugged to the bigger port on the intake. I suppose too much vaccum was bogging the idle. If you rev'ed it up hard and let off it would bog and die. I switched the lines and now it idles steady and you can actually rev it.