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

Tiny
JRSCARS
  • MEMBER
  • 2001 SATURN L100
  • 95,000 MILES
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.
Sunday, November 20th, 2011 AT 11:11 PM

14 Replies

Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
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.
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Sunday, November 20th, 2011 AT 11:20 PM
Tiny
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?
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Sunday, November 20th, 2011 AT 11:35 PM
Tiny
JRSCARS
  • MEMBER
  • 7 POSTS
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.
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Monday, November 21st, 2011 AT 4:10 AM
Tiny
SATURNTECH9
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Does the cooling fan run all the time?
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Monday, November 21st, 2011 AT 4:32 AM
Tiny
JRSCARS
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  • 7 POSTS
No, the cooling fan cycles as it should.
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Tuesday, November 22nd, 2011 AT 12:22 AM
Tiny
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.
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Tuesday, November 22nd, 2011 AT 1:44 AM
Tiny
JRSCARS
  • MEMBER
  • 7 POSTS
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.
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Thursday, November 24th, 2011 AT 5:35 AM
Tiny
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.
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Thursday, November 24th, 2011 AT 5:40 AM
Tiny
JRSCARS
  • MEMBER
  • 7 POSTS
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.
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Thursday, November 24th, 2011 AT 4:58 PM
Tiny
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.
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Thursday, November 24th, 2011 AT 6:45 PM
Tiny
JRSCARS
  • MEMBER
  • 7 POSTS
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.
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Friday, December 2nd, 2011 AT 3:25 AM
Tiny
RIVERMIKERAT
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  • 6,110 POSTS
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.
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Friday, December 2nd, 2011 AT 3:37 AM
Tiny
JRSCARS
  • MEMBER
  • 7 POSTS
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.
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Monday, December 5th, 2011 AT 11:24 PM
Tiny
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.
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Monday, December 5th, 2011 AT 11:37 PM

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