Ok well this will be a long one. First off I have a 91 Convertible Camaro, V8 305 TBI, 119k. About a week ago I was driving my car and out of no were it was shifting really hard in between 2nd 3rd gears (like head jerking, pounding sound hard). So first thought was ‘OH NO Transmission is GONE’. Well the next day it wouldn’t start (so now I’m freaking out!!). I start with the simple things, it tried to turn over, I heard the fuel pump kick on, and I got fuel at my TBI. So I then sprayed carburetor cleaner in my TBI and it started up fine. Leaving it alone for about an hour and it still stared up fine. Well thinking I’m out of the woods I leave it. The next day it won’t start again (now I’m just mad). I spray carb cleaner in the TBI again and it starts, yet now I’m getting an error code 21. WTF!! So I step back look at the problem a little differently. I then replace my Idle Air Control Valve, TPS (error code 21 ‘High voltage on TPS’ seems when I sprayed the carb cleaner in the TBI it sorted out the TPS), and for ***** and giggles my PCV valve and filter (they were dirty). And BAM….my car starts fine, runs great.

But the kicker is my transmission is fine now, no hard shifting. Question is how does replacing my IAC make my car shift fine?

 

Not sure, but I would check the kick-down cable to make sure it's tight and adjusted right..... better safe then sorry.