i have a 1987 camaro 350 tpi in my s10 blazer its running a 91 speed density setup in its been in there for about 5 years never had any problems but lately its been driving me insane it runs fine when i am driving it normal but whenever i get stuck in traffic for more than 10 min its starts going haywire the idle goes up and down it runs real rough it just runs like crap any input would greatly be apprieated also when i am on the highway it seems like its holding back if i accelerate hard where should i look first?

 

I would bet it's the IAC. Almost guarantee it.

Take off the throttle body and unscrew it, clean out the throttle body and the IAC. Sometimes you can clean it up and have it work, other times it's a replacement.

IAC is about $100.

 

just to add my 2 cents in.. i have heard of fuel injectors doing this when they start to go bad, does the surging get worse the more you drive?? i would get a volt meter and test them

 

THe IAC would have no effect on you highway driving.

 

Speed density is controlled mostly by the MAP sensor and O2 sensor. Ma want to look for vacuum leaks or try a new MAP.

 

well i bought a new map sensor ,new aic,new throttle posotion sensor,new air temp sensor,new o2 sensor it still doing it seems like only when the temp is very hot out side it does it when the temp is over 90 degrees the colent temp was at 200 any other things to look for?

 

hook up a gauge to the fuel rail and check the fuel pressure. did you swap fuel pumps when you did the engine swap? chances are it might be starting to go bad. high ambient temps means the fuel is hot, and electrical things dont like heat.

 

i have good fuel pressure its 41 at idle and 44 when i pull off the vacume hose the engine perfect when cold once it gets past 210 its undrivable and alot of black smoke comes out the exhaust

 

hmm, ok. sounds like maybe the ect sensor has gone bad and is telling the ecu that the engine is cold. does your engine have the 9th injector for cold start up? its located on the driver's side fuel rail. also, around the thermostat housing, there might be two temp sensors. if the cold start injector temp sensor is bad, its going to read to the ecm that its -40 degrees and cause it to run rich. its probable as you have replaced a lot of things already.

also, you checked the fuel pressures cold? try it again once its hot. it could also be the fuel pressure regulator sticking. mine did that once before

 

my cold start injector is not hooked up im running a speed density set up i changed every sensor map.iac,throttle posotion,new coolent temp new mat sensor it has good fuel presser cold and hot 41 psi at idle and 44 idle with vacume off