Pontiac Repair: Misfire #5 cyclinder, grand am gt, ac delco

Question
Hi Todd,
I have a 97 grand am gt, 3.1, auto trans 114k miles.  I have had problems with the car dropping #5 cylinder.  First start of the day, it runs fine and strong.  But after I make it to my first destination and turn of the car, say 5-10 mins, come back and start up again, it drops #5 cylinder and P0305 code comes up with the flashing check engine light.  After about 15mins of driving, sometimes #5 cylinder will come back and the engine runs fine.  I have replaced spark plugs(bosch plat 2), wires (bosch), all 3 coil packs, ignition module, #5 fuel injector, fuel filter, o2 sensor #1, fuel rail pressure is within book tolerance, ECM replaced, I've pulled the heads, replaced the gaskets, had the heads shaved, valves we're checked ok. Still same problem.  It seems to perk up if I use starting fluid sprayed in the intake which still leads me to injectors or fuel problem. While #5 cylinder is misfiring I can here all but #5 injector clicking. Should I replace all the injectors as a set or should I go in another direction?  Any info you can give is greatly appreciated and thank you for your time.

Answer
Hi George:
wow you have been around the problem but still haven't found it. did the problem start after the heads were re done or did you go that route to try to fix the problem? spraying carb cleaner into the valve cover is not an accurate test if the pcv valve and breather tubes are connect to the valve covers. the engine will draw it in through both of them. You changed pretty much all of the electrical parts so I would want to look at the mechanical side rather than the electrical side. when it does strat to miss I would want to do a compression test compair it to another cylinder when it's hot. Yes I know that back head sucks when it's hot but you can at least rule out a comnpression issue from possibly a valve or lifter problem. Also loose those bosch plugs! use only ac delco plugs. the other option is to see if it's dropping out spark or injector pluse on #5 you can use a spark tester in that plug wire and the large connection for the fule rail back probe the 2 wires for the #5 injector and see what your loosing. whenyou do that use either a digital volt meter or a computer friendly test light one with led's in it not a bulb test light the ecm will throw injector driver codes if you use a regular test light. just a few ideas before you spend any more money on a 100K mile car that's 11 years old. good luck :}