Hello everyone and thanks for viewing this post...
I have a '98 Grand Prix GTP and have owned it for about a year now... just recently started having a few problems with it.
I was driving and noticed some hesitation at highway speeds and when trying WOT for some passing... then the CEL (check engine light) came on... flashed a few times (knew that may not be such a good thing from prior auto ownership of other manufacturers... just a general rule... I guess)...
Anyways, took it to the shop to get a scan and poss some service...
Here is a list of the codes that came up and what wording came up beside them:
P0301 - Cylinder 1 misfire
P0336 - Crank Position circuit range performance
P0420 - Cat Efficiency threshold
Also, you should know that a couple months ago I noticed some pretty bad misfire/sputtering/loud exhaust issues while driving... took it to the shop to get it diagnosed and as a result got my plugs/wires done... my check engine light came on and even flashed as well as having some pretty badly fouled plugs! I wish I could remember the codes that came off that time, but I can't be exact but I'm pretty sure they were the same P0301, P0336, P0420... my car was cleared of all codes and it seemed to run good/better (the way it did from when I orig bought it). Thought problem was resolved... so carried on being a happy GTP owner...
My car is a stock GTP and when I got my wires/plugs done I was given 3 different options for plugs and I chose the second option (ranking obviously from 1-3... 3 being best; 1 being worst) and my wires were oem replacements.
Now I've done some reading on this site about the specific codes and have come to the idea that it may be a bad cat... my mechanic is thinking the same thing, but I will be sure to get him to see if there is any rattling going on there when he's got it up on the hoist...
One question I have is, is can I just cut the cat off to resolve this issue? Like I said it's a '98 and I'm the owner... I don't want to sell the vehicle, but I don't want to rule that option out later down the road (whenever that may be)...
My mechanic took it for a test-drive today and noticed the same hesitation and thought it sounded like it was being flooded and actually stalled the car and had to wait abit to start and drive again....
I've also read about switching the coils and see if it followed, which I may tell him that this is one thing that has been suggested by fellow owners that have had this/these same issue(s).
Anyways, that is where I stand. My car is at the shop right now, my mechanic has gone for lunch, and I took the codes from him to look up some possible causes and repairs...
If you have anything to suggest, feel free to do so and thanks in advance for any advice.
