Why wont the car start on a new coil but it will the old one? and it misses.

2001 SATURN L100
95,000 MILES
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JRSCARS
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Recently the car would not start and I diagnosed a bad ignition module. I replaced the module and the car started and ran fine. A couple days later it developed a light miss. It randomly but very regularly coughs, sometimes its bad, sometimes its not too bad. I did a basic tune up with plugs and a fuel filter. No change. I finally decided my coil pack was faulty, so I got one, it will not start at all on any new coil. I got one from the parts store and from the dealer. It will start back up on the original one, but still misses. I dont know what to do. Any thoughts on why no coil will work with it? thanks.
Nov 20, 2011 at 11:11 PM
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RIVERMIKERAT
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Could be a bad connector or a defective coil. New parts being defective are rare, but they happen. Make sure the crankshaft and camshaft position sensors are functioning properly, as well.
Nov 20, 2011 at 11:20 PM
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SATURNTECH9
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Just to add to this one does it only miss at idle or thru out the rpm range?Those engines that year are known for jumping timing chains?
Nov 20, 2011 at 11:35 PM
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JRSCARS
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Thanks for the quick replies. I ruled out the cam sensor because it wouldnt be so specific to which coil pack was on it, but maybe I have 2 problems. The car has most of its coughing at idle, worse in gear and with ac on. Off idle its much better,almost not noticeable.
Nov 21, 2011 at 4:10 AM
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SATURNTECH9
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Does the cooling fan run all the time?
Nov 21, 2011 at 4:32 AM
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JRSCARS
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no, the cooling fan cycles as it should.
Nov 22, 2011 at 12:22 AM
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SATURNTECH9
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At the dealer they sold you a single coil?When i worked at the saturn dealer they only came as a coil cassette both coils housing etc without the ignition module.
Nov 22, 2011 at 1:44 AM
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JRSCARS
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yes, to clarfy, i am refering to the coil as singular, but it is the assembly you are refering to. the module was replaced first when it had no spark at all. i have since run fuel injector cleaner through the injectors to rule them out as a problem, sure enough, no change in the miss, worse when its cold and/or under load.
Nov 24, 2011 at 5:35 AM
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SATURNTECH9
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Ok so you replaced the coil cassette/assembly are you sure you didnt get a bad module?Because you said it went from a no start to runs great to now runs poorly.
Nov 24, 2011 at 5:40 AM
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JRSCARS
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no, im not sure its not a bad module, just thought it was unlikely. my next step was going to be to find a coil assy off of the same car and try it. i can do the same with the module.
Nov 24, 2011 at 4:58 PM
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SATURNTECH9
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Thats a great idea i keep a spare coil cassette complete with module for a quick swap out makes trouble shooting a lot faster.Keep me posted on what you find.
Nov 24, 2011 at 6:45 PM
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JRSCARS
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I replaced the ignition module with a new one, the miss persists, also i notice when the lights are on everything flickers a little, but the battery is charging at 13.8. do i have a possible short in the ignition system? what a nightmare.
Dec 2, 2011 at 3:25 AM
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RIVERMIKERAT
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It sounds more like either the alternator going out or a ground issue. Check the grounds for the coil packs as well. Check the condition of all the wires.
Dec 2, 2011 at 3:37 AM
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JRSCARS
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Got a coil pack and module together at a salvage yard, it came off of the same car. it works, but only with the module that came with it. the module that was on the car will not work with the one i got from the salvage yard. It does appear to have fixed the miss. So apparently, coils and modules have to be sold in sets.
Dec 5, 2011 at 11:24 PM
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SATURNTECH9
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Thats why i always have a coil assembly with module to swap out.But i have never ran into the problem you had at saturn the coil came as a assembly less themodule.I would then swap over the module from the car and it worked great.But those were all factory parts.Maybe some of the aftermarket coil or modules have a compatiabilty issue?Glad to hear you got it figured out though.
Dec 5, 2011 at 11:37 PM