: 96 cadillac deville code after code?!?

04-18-06, 05:52 PM
Need advice desparately!!! After replacing a muffler it all started. . . First the engine light came on it was the bank one O2 sensor. Replaced that - scanned it and it kept reading this. Bought a different one and replaced both O2 sensors. Bought new plugs and wires. At this point the engine started missing and threw a P0308 code. Replaced the 8 - 3 coil pack. The car continued to misfire. Scanned on a hand held now reads P0305 and P1406. What next? I'm so frustrated. . Could this all be related to the muffler change? I had the car at the dealership and the mechanic looked it over for about an hour yesterday. That is when it was reading P0308. Replacing that coil pack just brought up two new codes!!! ??? I'm getting ready to sell this car and I need it to pass emissions!!!! (It did not have any problems prior to muffler change. . . )Any suggestions what to do next?

04-18-06, 08:58 PM
Just for the hell of it, clean the battery terminals and check the battery.

04-19-06, 07:58 AM
Great idea about trying to clean the battery. . . Unfortunately, engine light is still on. Internal code is current reading P0300. ANY other advice is welcome. We will try cleaning the EGR valve tonight. John thinks it may be the cat. (something we have not looked at yet)

04-21-06, 06:23 AM
i just bought a 98 deville with 60,000 and im getting the same P0300 code. check engine light is on all the time and dealer just replaced plugs....cant say for sure if he knew what he was doing but anyway let me know if the cats the problem....thanks

04-21-06, 02:10 PM
I had someone tell me to check the spark plug wires that we replaced. He says to only use AC Delco wires. He has seen Northstar misfire with the master market wires. We have not tried to switch these out yet. Our choices our buy another coil pack (since P0305 is showing) cleaning the EGR valve and the cat. I think we are getting closer. I will definitely post the cure as soon as I know she is running great again. . .

04-22-06, 08:34 AM
The engine light is off and the misfire is gone! We're back to business as ususal. . . We took the "new" wires off and returned them and put the original spark plug wires back on. Replaced another coil pack (two total) and the problem was solved. . . the codes are now history

04-22-06, 11:10 AM
so... was it the coil pack or the wires? These things are handy to know, you know...

In the interest of science, I'd recommend plugging the "new" wires back in.

04-27-06, 11:19 AM
I believe it was the coild packs (actually we replaced two). The engine light has remained off and it is not misfiring at all. I believe the wires were the originals ( must be AC Delcos . . .) I didn't realize how important GM parts are to these engines. But I guess it makes sense. Hey but I'm not a mechanic (I'm acutally a plumbers wife !!!) BUT . . . I've learned a lot about coil packs, spark plug wires and codes!!!!:rolleyes: