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1990 Oldsmobile Cutlass intermittent missfire

Tiny
JSHUFFMAN
  • MEMBER
  • 1990 OLDSMOBILE CUTLASS
  • 121,000 MILES
I have a 1990 Olds Cutlass Supreme. When it sarts in the morning it runs fine untill it gets warmed up, then it starts to missfire. I can smell gas also. Have replaced IAC valve, Temp. Sensor, and Ignition module. EGR valve was removed and cleaned. When I replaced the ignition module, all seemed well. Finished by putting new plugs and wires on it. Ran great for about a week and a half, then started to missfire again. After the car warms up you can shut it down, wait 5 to 10 minutes, then it runs like a new car all day long. It has a 3.1litre V-6. I have been around cars and repaired them all my life, but this one has me stumped. Any ideas?
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Wednesday, November 13th, 2013 AT 12:02 PM

7 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Maybe one of the coils is failing?
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Wednesday, November 13th, 2013 AT 3:18 PM
Tiny
JSHUFFMAN
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  • 12 POSTS
When I tested the ignition module and found out it was bad I also tested the coils with an ohm meter, but the car was cold at that time. That answer could be the problem while warming up. Thank you for the idea, will let you know soon. Will test them in the morning.
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Wednesday, November 13th, 2013 AT 3:33 PM
Tiny
SATURNTECH9
  • MECHANIC
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That's about all you have left keep me posted.
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Wednesday, November 13th, 2013 AT 10:10 PM
Tiny
JSHUFFMAN
  • MEMBER
  • 12 POSTS
Well, after a shocking experience I figured out that #4 cylinder was my miss fire. Correct me if i'm wrong, but when a coil pack goes, shouldn't both sides of that coil show bad? I dissconected each wire from the coils one at a time. The coil pack for cylinders one and four are the same one. Cylinder one fired, but cylinder four had missfires. Tested good with the ohm meter, so I went back and made the parts store swap out the ignition module. Gotta let it get cold again so I can see if it works. Let you know.
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Thursday, November 14th, 2013 AT 10:06 AM
Tiny
SATURNTECH9
  • MECHANIC
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I have seen coils with two posts one fire one not and it's a bad coil.
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Thursday, November 14th, 2013 AT 10:15 AM
Tiny
JSHUFFMAN
  • MEMBER
  • 12 POSTS
Well, after letting it cool down, no problems. Could have got a defective module. If it missfires again at least I know what coil to replace. Thanks for the help. This is a great web site. Glad I jioned. I'll keep you informed and also try to help when I can.
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Thursday, November 14th, 2013 AT 2:09 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
The ignition module isn't going to cause just one cylinder to loose spark. You can always swap the coil with another cylinder to prove to yourself u have a bad coil. Glad you like our site.
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Thursday, November 14th, 2013 AT 4:20 PM

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