On a 2000 Saturn SL2 1.9 twincam,problem with misfiring on cyl 2 and 4 sporadicallyan when checked with computor analyser , at idle advance varies from 4 to 23 degrees. Coil plate was suspected and coil pack replaced with no change.Would you suspect defective sensor or computor? Thanks.

SOURCE: Random Cylinder Misfire

Get a Haynes manual for your vehicle and use the troubleshooting guide there.  about $20 from amazon, auto parts store or haynes.com.  This WILL save you time and shortcut this and any future diagnosis. Haynes IMHO are top notch and I like them better than some factory service manuals that fgo for $100 and more.

David, 99 Saturn,  Cam position sensor codes seem to indicate a engine timing (not spark, but crankshaft/camshaft sync).  Old timing belts or worn tensioners can cause belts to jump a tooth or two which can have a pretty dramatic effect.  The belt could also be old/dryrot and have lost a tooth or two causing it to jump.  If any of these are the case, or if the timing belt interval is near,  replace timing belt, tensioner, idler roller if present and water pump.  FYI, quality OEM ignition wires shold last at least 10 years.  If they are really bad, you can open the engine compartment on a dark night and you will see sparks arcing between them and/or something metal nearby.  We all replace wires when we are not sure what the problem is, and regardless of what anyone tells you, it only rarely solves anything unless the car is more than 10 years old. 

good luck.

SOURCE: replaceing coil pack on 1996 saturn sl1

Sounds like the Ignition Control Module.

SOURCE: vibration in motor

If you have the car computer scanned, which many auto parts stores will do free of charge, you will be able to retrieve a code that can point you in the excact direction of the problem. Without being there myself, the only thing I can say to try that I did not see mentioned is to check the fuel injector on the #4 cylinder. They sell a tool called a noid light, you can disconnect the injector and connect this tool to the wires to see if you are getting an injector pulse. If you are getting a pulse then you may have a bad fuel injector.
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SOURCE: 1995 saturn sl2 code 32

Hi. The EGR valve is a very sensitive issue. Buying a used one will always result in a continuing fault code. I recommend purchasing a new EGR valve. Before you install it, be sure to clean the EGR housing thoroughly. there can be carbon build inside where this valve is inserted. this carbon will trip the code if its not cleaned out properly.


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SOURCE: 2000.saturn 3.0l 1,3,5, cylinder missfire.

Spark plugs. I recommend just replacing all of them.