hey guys i have an 86 iroc a 305 tpi... any way when ever i start the car it runs decentaly ruff untill it is warmed up.... i have sat next it and listend to it and it will eventually all of a sudden just like the flick of a switch start idleing perfect.... it doesnt idle bad when warming up just kind of ruff and doesnt clear up till it gets to a certan temp and then like i said as if some one flicked a switch will run perfect... also it seems like my car is lacking alot of its power and is very very bad on gas ... more then its suposed to be... so there is def something going on with it.... when i punch my CAT with my fist it rattles... so maybe a clogged cat.... im all ears guys.. does this have soemthing to do with going into open/closed loop mode or something. i am going to do a complete tune up on it and replace everything sensor wise, cap , rotor, coil, plugs, wires, feul filter, tps, cts, do u guys have any ideas to what i could be experiencing....

Possibly could be a bad O2 sensor.It seems as though when the ecm goes into closed loop it runs fine.As for the cat,knock out the insides or try replacing.Could be a real good reason for the poor performance and fuel mileage.

Ok yes it does, your car has cold start injection. You will notice on your fuel rail on the drivers side you will have an extra injector between your runners ( the injector wires are brown I belive). This extra injector is active when the car is cold to aid in start up and cold running. In the front of your base manifold is a sensor like a coolent temperature sensor. This sensor controls the activation and deactivation of the extra injector. It sounds like your injector is not working, you can pull the plug check for voltage when the car is cold at the plug and also check the ohms on the injector. The next step is check the sesor in the front of the manifold. Check for voltage at the plug and check the sensor. Hope this helps, it not the 02 sensor I have seen tons of issues with the cold start systems.

As far as bad gas milage and lack of power, could be all cured in a tune up, however check your fuel pressure at idle, WOT to make sure your regulator has not gone bad. 02 sensor will affect gas milage but not WOT power.

im going to look into all of those things....

could my o2 sensor be bad and not make the engine light come on at the same time....

the other day i put two bottles of fuel injector cleaner in the gas tank and let it run for about a half an hour.... i wasnt able to take it up the road because i took it off the road to be rebuilt from the ground up... right now im just dealing with the engine first... any way the next day it fired up like on the first crank after i turned the key... and before it took a couple cranks....

do u think the feul injector cleaner actualy cleaned something out making it run a bit better... i know it should run way better but the feul additive did seem to help alot atleast on start up it did...
im going to go ahead and do a complete tune up any way and let u guys know what i find out...

if u have any insight on this let me know im all ears... i mean this is a good engine.. doesnt burn any oil and holds 60 psi of oil pressure all day long so i want to get it running good and use it a bit longer before the 400 goes in...

TPI is an odd fuel injection, I had a bad TPS and no check engine light. So don't rely on the dummy light for everything. Very well could be a clogged cat most are only good for 70K miles, but once agains depends on use of the car. Try the tune up examine the plugs to see if you are running rich or lean. Check the fuel pressure our fuel pumps are always going bad. Open and closed, ok when you first start you car in goes into cold startup which is open (not reading o2 for adjustment) when operating temp is reached it goes into closed loop (app. 165-175 degrees F). When you floor the car and the computer reads over x amount of tps voltage the car goes into open loop however this is a different table than the startup table ( different injector pulses, and timing curve) Your bucking a flooring the car is the transition from cruise closed loop to open loop wot. When this occurs there is a quick increase in fuel (like a accel pump on a carb) if the fuel is not there due to a fuel pump or to much fuel (to high psi rail pressure) due to falty regulator that will give you the bucking and in the same area if you are adding more fuel in short period of time the ingnition must be able to keep up, if the extra fuel is killing the spark it will buck due to insignifigant burn. If your regulator is bad and has increased the fuel pressure this will give very poor gas milage. Hope this helps I am done. Good luck (by the way this was a basic run down on closed loop open loop cold start table, warm cruise table and is over simplified to eliminate confusion, and no I am not a know it all, just drunk)

thanx alot for the help man... ill add an adjustable feul pressure regulater to my list of tune up parts.... i might as well get an adjustable one... and ill set it around 45-50 psi like i have been told is the best for power delivery...

Did you ever fix that cold start problem? my car seems to be doing the same thing. It is getting to the point where i have to keep my foot on the gas to keep it running while it is cold.

Change your plugs and O2 sensor