ok this problem has plagued me for a long time over a year....no one i have asked knows whats wrong with it....on cold mornings and recently it has been doing it on somewhat warm mornings 50 and lower......when i start my car up...it idles just fine for 5-10 seconds then it generates a misfire...and i mean it sounds like a dead mis in a cylinder...it shakes the car when ur sittin in it......when it warms up it used to stop...but now it will pop every now and then.....here is the really weird part....when its doing its dead mis thing....its in park....if i put it into gear with my foot on the brake it stops and idles fine...if i let go of the brake and coast itll have a dead miss again while its moving....as soon as i give it gas in gear it clears up...u can accerlerate fine...lets say i get up to 30 mph and let it coast...you can hear the miss fire poppin in the exhaust until it warms up.....and im not a newbie...ive replaced just bout every senor there is...done many tune ups..ive changed...plugs, wires, cap,rotor, oxygen sensor,IAC,TPS,EGR,MAP,EGR position sensor,CTS,coil, pretty much everything...only thing i can think of i havent done is the stator...i dunno if that can cause it but i guess it worth a try....while im at it..i got a TBI rebuild kit and new injectors so im gonna toss those on and im taking my TBI spacer off incase for some weird reason that it causing it....any info would be great...this has been plaugin me forever...

 

have you checked the injectors? you said your dealing with a TBI motor first thing i would do it get a timing light hook it up just liek you would if you where checking timing but don't put the light on the blanceor take the air cleaner and the little spacer thing off and flash the light by the injetor so you can see how it is spraying... then crack the the throttle up some and watch how the injetor sprays i have seen this be the cauz of the problem your talkign about. make sure they are not dripping or comeing down in big blogs when you go on and off the throttle also check for vac. lecks as this can cause the type of misfire yoru talkign about i see you already replaced that IAC motor this where i would of started out.. it also wouldn't hurt to do a compression test and when you have the timing light out check the timing don't forget to disconnect the tan wire for the computer advacne take a can of brake cleaner and spray down everythign you can thing of that could be cause a vac leck... all the hoses the throttle body base to the intake the intake its self (check the back of the intake as this is where SBC's like to blow out gasket) if you still find nothign after all this i would unplug the ECU let it sit for 30sec then plug it back is... it your dealign with an OBDI car after you plug the ECU back in the car will run like crap untill the computer relearns the motor. this is normal. after that if your still having problems i'd check out the Knock sencor since if this sencor is bad it will terard your timing. (passagerside of the motor under the head in the block maybe EZer to see from under the car/truck) have you checked the ATS ? (Air Temp Sencor) also the coollet temp sencor that is in the T-stat housing should be checked... what this sencor dose is tell the ECU hoe hot the coolet temp is if its tellign the ECU thats its only 22º its goign to richen the fuel up so it will runnig better in the cold it can also work the other way around it can tell the EUC that its running at 210º right when you first start it and it will lean the fuel out and this can cuz a mis also make the motor ping and then the knock sencor will pick that up and will retard timing

Good old computer controled cars.... i'm happy i removed mine out of my 1991 firebird :-D

also if you can find a local parts store that dose free check engine lights code finder and that are useing the actron super scaner put in your year make and model then go to view data do this with the car running.. this will give you all the info that each sencor it tellign the ECU good way to just look it over and see if you find some number that just don't sound right

if i where you i would print everythgin i jsut said out and you can go wench on your car/ truck and not try one that then back back to the computer and reread the post that will save you some time as i knwo how much it sucks to work in the cold! good luck man and let me know

 

ya ive done the colant sensor...i havent checked the knock sensor but im pretty sure the knock sensor turns the check engine light on and its off....i also recently hooked my car up to a nemesis....it gave me live data on all my sensors and they are in spec....i have a whole tuned port system in my garage i might just toss that on there and see if it runs better

 

easyer said then done... but well worth the work when its done :-D