Hello ,working on a 1990 Seville. misfire terrible,very low power ,poor idle, Installed new plug wires, Dist. cap & rotor,AC spark plugs. 2 middle front cyls. and 2 middle rear cyls. not firing. Compression good. Spark to Spark plugs. all hoses appear ok. Fuel pressure 36 psi, recent new fuel pump and filter and air filter,14 volts, 81,000 miles.....Help please

 

Check injector fuses there are 2, if ok install noid light in dead cylinder injector connectosr and see if it blinks.

 

If this is a throttle body injected engine, you have one injector(out of two) that is not firing. Could be a fuse, as slowroll says, or a bad injector. Noid light(or a test light) plugged into the injector harness will tell you if the ECM is firing it. If it is, but the injector is not spitting any fuel, the injector is bad.
Another possible cause of a bad mis-fire on those specific cylinders is a severe vacuum leak.
hth

 

Hello, Found one fuse blown of 2 going to injectors. Now it runs much better;but misfiring still. Think the car got bad gas and maybe some injectors are stopped up. Put cleaner in the gas tank too. Injector harness is hard to access. Found out the gas tank had been cleaned before and a new fuel pump installed. I have seen old gas that looked like a duck at the Valdes oil spill. Black and gooey. Will keep running vehicle for a little while to see if running might unstop injectors. Thanks. I used to drive v8-6-4 cadillac. Thanks for your time and help.