I have a '97 Seville and have been experiencing rough idles at startup and poorer than normal gas mileage recently, so i decided to pull the plugs and wires and give them a good clean down. I cleaned everything and sprayed carb cleaner down into the holes where the plugs sit and cleaned them with a dry rag. After I was all done, I put the plugs and wires back into place, just how they were before. Now, the car has an intermittent shudder when driving throughout the RPM range. I can rev it all through the RPMs in park with no shudder at all except the very start. I am hoping that this is all just ignition related because that is the only thing I messed with and the transmission was fine up to this point. This just happened today, and tomorrow I plan on pulling out everything including the coil packs to clean and then regap the plugs. The plugs and wires both have under 2k miles on them. Any recommendations? Lucky day to have a coil pack break? Thanks in advance.

Have you had the duel rail recall done? Common problem afterwards. Been there, done that. Replace the wires with OEM A/C Delco wires.

Is there a way that I can tell if the recall has been done? This is not the same motor that came in the car. Mine was replaced with a 10k motor at 150k.

If the recall has been done, the fuel rail will be stainless steel. If not, it will be black plactic. That said, if the motor was changed, they may not cover it if it was a motor out of something other than '95 - '97. If it hasn't been done, take it in. The worst they can say is no.