Rough idle at start along with other issues

I want to thank those that can help....
 
I have a 1993 cadillac seville with idle and surging problems. At first start and after cooling off the car does this along with a rough shaking of the car. During the idle if I mess with anything electrical the idle gets rougher and the idle gets lower. I''ve changed the wires and plugs and the same thing has been going on.
 
If anyone an help me out i greatly appreciate it.

4.9l or northstar

im sorry its a 4.9

i know the code 12 means theres nothings wrong but its also pulling up code 31 when my a/c compressor turn on the car shakes not one time it fell dead. ima try sea-foam but what would be the next step if that doesnt work.

Possible plugged fuel injector. Try removing one plug wire at a time, engine running, to locate the cylinder that runs the same with the wire off. Then post back.

Code 31 shorted map signal. Do you have factory service manual?

thannks carnut ill try that. slowroll i dont have a factory service manual, what is the map signal for.

MAP sensor is main computer input for engine load. MAP sensor signal voltage effects timing and fuel control. Shorted MAP sensor,ECM, or sensor wiring can cause your concern.

sorry slowroll it took so long to reply.i did change my ecm and its doing the same thing. is there anyway the i can test the map sensor out. what should happend if i unplug the map sensor, and what do you mean by sensor wiring. when i turn my head lights on and put the car in motion thats when it surges as well as turning the a/c on and when the compresser kicks in it does the same thing, could this be a electrical problem

i did change my ecm and its doing the same thing. is there anyway the i can test the map sensor out. what should happend if i unplug the map sensor, and what do you mean by sensor wiring. when i turn my head lights on and put the car in motion thats when it surges as well as turning the a/c on and when the compresser kicks in it does the same thing, could this be a electrical problem

what if you do a static cranking compression test and a running compression test, this could see if the engine unbalanced. lemme know if im wrong but get a vaccum gage that can read compression also and diconnect all spark plugs. disable the fuel and ignition system [might take some research to find how] hook vaccum gage onto spark plug hole[where the spark plug was] and crank it up. let it go through 4 cranks. Take the measurements down for all cylinders. The first crank should be 50% of the last crank and the final crank chould be at least 100 psi. all the cylinders should be within 20% of each other for the last crank reading. If there not then the engine is going to be unbalanced and run rough. If theres an unbalance you can do a running compression test. Put back all the spark plugs except the cylinder thats messing up. Ground the wire to a test light or something and turn the car on. at idle it should have at least 50% of the last reading you got for the cranking compression. Then flore it for just a sec. or two so it can take in some air. That reading should be 80% of the last cranking compression reading. if you dont get the results that an engine thats Mechanicaly sound then you can fill the cylinder with compressed air when its on top dead center of compression stroke and listen where the airs coming out of. Is its coming out of intake the you have intake valve problem. If out the exhaust then exhaust valve prob. Out the oil fill hole then you have worn piston rings. I hope this helped, ive had a couple beers so ill have to check what i tpyed tommorow.

thanks for the info,ill checked and get back with you as soon as i can....thanx