joeb Posted October 31, 2004 Report Share Posted October 31, 2004 i have been chasing a miss for about 10 months. new wires and plugs. no codes. i put another set of delco wires on 2 weeks ago and it seemed to run better but yesterday i got a code P0300. and it ran even worse. i tried a set of champion platinum plugs 6 months ago and use them for about a month but took them out since they did not seem to help. as a last resort i put them back in this weekend and now it seems to run ok. all of the old plugs look the same. nice light color. would a pro scan tell me which cyl. is running bad? of course i need the P0300 to come back for that. how about in injectors? or intake gasket? Link to comment Share on other sites More sharing options...
Logan Posted October 31, 2004 Report Share Posted October 31, 2004 Some GM and other vehicles will set a PO304 for misfire cylinder #4 (example). The Cadillacs, strangely, will not. All you get is a PO300. A GM Tech 2 does have a misfire graph that will show where the miss is... http://images.andale.com/f2/115/106/376867...11783_tech2.jpg Have you tried swapping a new coil in? Logan Diagnostic LLC www.airbagcrash.com www.logandieselusa.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
joeb Posted October 31, 2004 Author Report Share Posted October 31, 2004 how do you go about changing out the 4 coils? get 1 new coil and put it in and check vehicle operation and than move the new coil to location #2 and #3 and finally #4? seems like a hit or miss type scenario. are the coils on a 98 buck 3800 the same as the caddy? i had a 2.8 chevy mpi engine that lost a coil a few years back . it barely ran on 4 cyl as you would imagine. my sister had a 2.5 grand am that lost a coil and it ran on one coil. i still think it partially failed. how could a 4cyl engine run on just 2 cyls? Link to comment Share on other sites More sharing options...
Logan Posted October 31, 2004 Report Share Posted October 31, 2004 Without any diagnostic tools....thats the fastest way.....buy 1 coil and start swapping them out 1 @ a time... Logan Diagnostic LLC www.airbagcrash.com www.logandieselusa.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
Logan Posted October 31, 2004 Report Share Posted October 31, 2004 The Buick coil should be the same as the caddy. That is if the buick has the individual coil version. The Buicks had 2 versions....one with individual coils....the other had a solid all in one coil pack... Logan Diagnostic LLC www.airbagcrash.com www.logandieselusa.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
Barry94 Posted October 31, 2004 Report Share Posted October 31, 2004 Did you do a compression test ? How do you know you're not fighting a mechanical problem.. Barry 2008 STS V82016 Colorado Z711970 Corvette LT-1 Coupe Link to comment Share on other sites More sharing options...
maydog Posted October 31, 2004 Report Share Posted October 31, 2004 I had a miss due to a coil a few weeks ago. I borrowed a auto x-ray tool from a nearby checker. My DIC would only give a 0300 code, but the scantool gave a 0303 and that was the coil. One of the outputs was shorted internally. Its a lot quicker than trial and error. Link to comment Share on other sites More sharing options...
joeb Posted November 1, 2004 Author Report Share Posted November 1, 2004 i let it sit overnite and it started fine in the morning. i drove it on 2-3 short trips to the store and it runs fine now. maydog, did you have a bad coil where the car was running on only 6 cyl? or was the bad coil failing intermittantly? i did spray the coil input connections with some contact cleaner. i had some dielectric grease around but i can't find it. if the problem comes back i will try swapping a coil from my buick. Link to comment Share on other sites More sharing options...
maydog Posted November 1, 2004 Report Share Posted November 1, 2004 I had a miss in only one cylinder. One end of the coil output had a hard short internally. Therefore, I was running on 7 cylinders. Link to comment Share on other sites More sharing options...
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