Hey guys,

The name is Justin I'm out of Sacramento and am driving a 2000 GTP, Supercharged bone stock. She's got about 190,000 miles on her. I love love driving my car so much that I drive for the ridesharing company Lyft, the pink mustaches. My passengers love my car as well. I'm also a graphic designer.

So I've been following this forum for about a year now up untill this point I have had all my Grand Prix problems solved and I wanted to thank you all for this!

Recently my car started running really rough, it started while idling now it has gotten to the point to where now while in motion it runs like crap. My car did throw two codes, P0203 and a P0303. I know that this is a fuel injection problem so I am guessing this is where my misfire is coming from.

Here's what I found I have done so far... First I checked all the connections and everything was nice and tight, no loose harness and no visble tears in the wires. Second I moved the injectors around to see if I could isolate the problematic injector but the problem stayed on the third cylinder, I moved it back. Lastly I picked up a noid light tester and it was giving off a signal, I checked em all to be sure. But here is where things started to get complicated....I noticed over the last few days that when I start my car in the morning and head off to work, the car runs excellent. It's not until I drive the car for a few miles it starts running rough. The car now, when going over 2000 rpm, starts shaking and the SES light starts blinking. But this is only after the car warms up. So I did the noid light test again after a cold startup and it was giving signal, I waited till the car warmed up and tested the no. 3 injector connection and sure enough it wasn't blinking at all.


I have no idea where to go from here. I'd really appreciate any help I can get!

Thanks!!!!