I have a 1997 saturn sw2 that stopped runnuing changed fuel pump wont idle error code #4 cylinder is miss fireing changed ignition module car starts runs ruff changed spark plugs & wire set

DTC P0340 will set if the PCM voltage on cylinder #4 signal wire is not pulled to ground (cam signal pulse) when:
Diagnostic Aids
Important: A cam pulse missing may not affect engine operation.
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An open or high resistance on the #1 plug wire or plug will result in DTC P0340 setting.

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Inspect the EIS towers and plug the wire connections for corrosion or other signs of poor retention at connections.

The electronic ignition (EI) module supplies a signal to the PCM whenever it determines that the #4 cylinder fired on its compression stroke. Because of opposite coil tower polarity, the simultaneous fir of #1 and #4 cylinders are of opposite polarity as well. Under most conditions, except decel, the waste spark cylinder fires before the compression cylinder in sequence. The EI module can determine this polarity sequence and voltage amplitude by using capacitive pickup plates located under the 1/4 coil. If the module senses a positive to negative sequence and high negative spike when #4 is on TDC, it pulls the PCM cam signal to ground signaling that #4 has just fired on compression. This signal along with the double pulse received from the CKP sensor, synchronizes spark and fuel timing.
Beside plugs , plug wires need to be replaced as well !

Does the car loose power before stalling or does it simply die without warning? If it loses power first, you're likely looking at a fuel pump or fuel system problem. If it just dies, you probably have an ignition problem. Does the check engine light come on before it dies?

The engine coolant temperature is high. Your other Codes are for missing cylinders on cylinder 1,2,3,and 4. Get the Codes cleared and start over. Changing the plugs and wires,etc could have generated the missing cylinder Codes.

Autozone,Advance, and Oreilys will scan for free.

Check your engine for an IDLE SPEED CONTROL SOLENOID, which may be in the intake. Or a fuel pressure regulator.

A lot of times people work on the spark side and forget the fuel injectors. They can cause a miss.

The P0304 indicates the #4 cylinder is misfiring. The flashing light means the cylinder is not firing at all...It could be several things causeing it, coil, wires, plug, injector or vacuum leak. Do not drive your vehicle until you have this repaired, as it will lead to further more costly problems. Good luck, i hope this helps.

this code indicates multiple miss fire,which is not just one cylinder doing it.if this motor has a vortec motor in it the problem could be the injectors not operating properly or the lines to the injectors may be leaking into the intake causing a rich condition.it could be the egr valve stuck open just a bit causing a vacume leak and rough running.it could even be a problem with the pickup coil in the distributer or a cracked magnet.the ignition module could also cause the problem.

It could be a bad computer that doesn't fire the fuel injector on that cylinder. Or, the fuel injector is clogged on that cylinder.

The fuel injector should have a telltale click when listening to it operating on that cylinder, and it should also make a noid light blink indicating current is getting to the fuel injector, when the fuel injector harness is connected to a noid light.

Good luck on this repair.

Have you checked the fuel pressure? Fuel pumps are a common failure item on those trucks. Pick up a cheap fuel pressure gauge and hook it up to the shrader valve on the fuel rail. With the ignition on and you should have 55-65psi. Even if it's a few psi below spec it could stop the engine from firing.Once you determine the fuel pressure isn't adequate make sure you have a good power and ground at the fuel pump. If that checks out, time for a new fuel pump module. I recommend only replacing it with an AC delco unit, I've heard bad stories about aftermarket replacements.
You could also spray some carb cleaner or starting fluid in the throttle body and crank the engine over. If it runs for a few seconds after spraying starting fluid in you know you have a fuel delivery problem.

sounds like a fuel pump reley you can change it cheep and it is usualy the fix for this problem

Double check the firing order and the plug wiring. My guess is at least 2 cyl are wrong ;-) Also it could be that the plugs are 'gapped' too big.

Guys at Autozone, Checker or PepBoys will help you for free

yes it is the ignition coils . po304 is a miss fire on #4 cylinder.wires and plugs should fix the problem unless ignition coil is not firing. there are 2 coils they run 1&4 2 &3 cylinders.