Engine cylinder misfire?

Hi there,

Remove all the spark plugs, and earth the coil lead, with a helper, place you finger over No 1 plug hole (front plug) get your helper to crank the engine, just a key on and off type crank, just enough to turn the engine a little, do this until you feel pressure building up on your finger, this will be the piston starting to compress the air in the cylinder, now with the key off, turn the engine by hand, ( this should be easy with no plugs) till the timing mark on the pulley reaches "0" on the timing scale, this will be TDC No 1.

Mark (mhpautos)

If no load on engine you should not be raising the RPM that high as you may cause an internal engine failure
and to prevent that from happening the PCM will shut off injectors to limit the RPM
Reason for it cutting out

Defective injector or burned valve. A cylinder leakage test can identify if a valve is not sealing.

Are you saying three different cylinders are misfiring? If so, look for something they have in common. Low fuel pressure is one thing. If you have the dual overhead camshafts, check for a jumped timing belt.

Injectors should be replaced in matched sets so they flow the same amount of fuel. If only one or two are replaced, some cylinders will always run a little lean. The oxygen sensors will detect the unburned oxygen in the exhaust and the Engine Computer will command more fuel from all of the injectors.

If there's a leak in the fresh air tube between the mass air flow sensor and the throttle body, some unmeasured air will get in and there won't be any fuel to go with it. That can result in a lean mixture misfire.

The next thing would be to connect a scanner that displays live sensor data so you can see what the Engine Computer is seeing. That will provide some insight as to whether the computer is commanding the wrong amount of fuel based on an incorrect sensor value, or whether the engine is misfiring in spite of correct sensor values. It takes an experienced mechanic to interpret the sensor readings.

Have you checked fuel pump pressure? Also, have you checked for vacuum leaks?

Kith, first, thanks for the positive feed back back. It's appreciated. Second, let me know what you find.

Joe

I have a 96 mercury sable that is missing when i'm stoped the engine light is on but the light will start to blink on and off then she will miss even when i'm moving and it seems that she starts to get to much gas and looses all power I had it in the grage but there are too many code to know where to start from will I have to replace all the parts the grage listed?

Two tests you haven't done. Compression test, and test of the fuel injector at #5! Let me know what you come up with!