View Full Version : 2003 northstar misfire

02-18-10, 12:25 AM
Need help,i have a 2003 seville sls with approx. 140,000 miles on the clock problem is i have a service engine light on and blinking.Had it to auto zone to read code it came up #4 cylinder misfire.Pulled plug soaked with fuel no spark.Replaced plug/coil boot and new spark plug started car, again rough idle pulled plug again still wet with fuel.What next???
Thanks for any info.

02-18-10, 05:21 AM
So sorry for the shipping mix-up Greg - when you get that coil swap that in place, it should solve your problem. If it doesn't it'll be the injector flooding the engine. I was told that was a perfect running engine I removed that coil cassette from (I bought it from another forum member - ponyboyt) so if it works good for you, please pay for it as we discussed, if it doesn't, throw it out and buy a new one. These coils do, on occasion, fail- as with all cars. The problem with these is if one coil fails, the whole cassette needs to be replaced....

02-19-10, 03:10 PM
Had a coil go bad on mine at just over 50k miles a few months ago, most likely that is it. Unfortunately it necessitates the whole cassette replacement at a cost of ~$230 from GMPartsdirect.com.

If that isn't it, then it's the injector.

02-19-10, 06:22 PM
www.rockauto.com may have some OEM DELPHI coil cassettes for your car with ICM for less than $200 apiece. (The 2 cassettes are identical except for color, so at 6:26 EST it looks like you have 5 choices tonight - with ICM those are a steal...........)

Don't forget to check the coil-plug connector boots and cassette ground spring also.

02-19-10, 07:12 PM
I had the front coil cassette fail on my 2000 STS a few months ago with 110k miles. Rock Auto had the best prices on them!

02-23-10, 10:48 AM
Had a similar type misfire on my 2003 sls, found some white chalkey type corrosion under the coil pack where the springs touch the electric contacts, cleaned it up and problem went away. Also make sure you use some dielectric grease on the contacts when your putting it back together.:thumbsup: