Flashing SES?

[stlmo_gtp]

alright so i am hoping someone on here will be able to help me out with the problem i am having with my car first of all the car is a 98 GTP with the following mods Custom Tune,SSAutoChrome Headers,NorthStar Throttle Body with LQ4 MAF,Alt. Rewire,ZZP Shiftkit,SmoothFlow MPS with 3.4 Pulley,SLP Power-Flo Cat-Back exhaust,160 T-stat,ZZP Ported Lower Intake, Stage2 Ported Blower,1.84 Rocker arms w/ pushrods.... car has been running fine for the past 3 months and then the PCM went out so i replaced that last week, along with the o2 sensor because that went bad aswell, well after i put in the new PCM i flashed it with my tune so everything wouldnt be messed up and it drove fine for about 5 days and then today when i went to start it up it fired right up but then after being idle for about 4 minutes or so the check engine light just started flashing and my fuel trims went really lean (10.9) and the car just idled really rough, anyone ever had this problem before? or maybe someone would be able to help me out on where to start cuz i have never seen a check engine light blink before lol

[TheOtherNick]

You have a miss fire. Find out which cylinder. I bet an injector **** out on you.

[stlmo_gtp]

alright cool thanks man gives me a good starting point i first thought a miss fire aswell but then the more i thought about it i didn't see how a miss fire would cause it to run lean, either way i will check both tomorrow

[TheOtherNick]

The injector is not spraying fuel so the cylinder is not firing causing the miss. No fuel in cylinder = lean cylinder = lean 02 reading = positive fuel trim adding fuel to other cylinders to get the a/f in check

[stlmo_gtp]

alright figured i would update everyone hooked up my powrtuner and it read misfires on 1&4 so i swapped the coils and it is still reading that it is on 1&4 maybe ICM? about to check the plugs right now because my buddy just said that he had on crack but i figured i would just use processes of elimation to figure out what is going on

[gumbo76]

You still having these problems? I just had my SES start flashing on me, and my '01 GP GT kept stalling out. I had no power beyond 3000RPM, and my mileage tanked hard. Took it to the shop and they were finding misfire codes. Found out it was a plugged Cat Converter. Picking the car up tonight from the shop. They dumped the exhaust and ran it, and it went fine. no misfires. $625+ later, I'll keep you posted.

[Scimmia]

http://www.grandprixforums.net/f17/l...nty-11743.html

This is what gumbo is talking about, but it only applies to the L36. Totally different issue, especially since the OP is running headers.