Thread: 2006 GP idling rough, already replaced plugs and wires.

I have a 2006 Grand Prix, and have had very few problems with it, until the other day it suddenly began idling very rough, and the check engine light came on. I had AutoZone run their computer on it, and it showed three misfires. It has 100k+ miles on it, so the most likely thing was a tune up, which I just finished this afternoon with the assistance of my uncle. He was concerned that there was something more, because none of the plugs or wires really seemed bad, plus it was a sudden change in performance. But we never heard any signs of a vacuum leak, nor smell gas from possible fuel injector leak. So as I go to put the cover back over the engine, I notice the elbow for my PCV is completely broken in two and we zip back up to AZ grab a new one, and slap it on. By this point I'm a bit flustered that I missed that, but as it has 100k+ miles it was due for a tune up regardless. However, when I cranked it up, there was NO difference at all in performance! I actually think I might have broken the PVC elbow while laying across the engine changing the back plugs, and that was just a fluke. I have also noticed that my cruise does not work, and it is temperamental when it comes to starting up.

Any help is appreciated!

tl;dr: rough idle, new plugs and wires, new PVC elbow, still rough idle. Also, cruise doesn't work, and iffy when starting it up. What do?

Remove the TB and clean the entire thing until it shines. The backside of the butterfly gets carboned up and can cause all sorts of strange issues. Then get yourself a can of CRC MAF cleaner and remove the MAF and spray the crap out of it, let it dry, then reinstall. As long as you fixed all your broken vacuum bits, it should fire up and run like new. You may need to get a new TB gasket when you reinstall. Not sure on the newer models.

Also, make sure you install stock irridium or copper plugs. These ignition systems will NOT work with Platinum plugs.

As far as the cruise control goes, I'd check the owners manual for the fuse(s) for this and start there.

Awesome! I will try that tomorrow afternoon!

I did go back with the iridium plugs, so that shouldn't be an issue.

If anything is an issue with the tune up, it is likely due to my relative inexperience in mechanic-ing, but I am confident that I got everything secure and in proper place.

i figured the cruise was likely as simple as a fuse, but the timing of it made me think it might be relevant due to a potential vacuum leak, but as I understand, it is just an electric cruise.