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Cylinder 5 misfire trouble code P0305

M

michellebuck76

New member
My 1999 Grand Prix (Supercharged 3800) has a little hitch in her gitty up. Ran a diagnostic and the trouble code came up P0305, cylinder 5 misfire. Makes sense right!? I have changed out the plug, wire, and the coil and she is still misfiring. Any suggestions as to a solution would be greatly appreciated. Thanks in advance, Michelle
 
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Could be a cracked head gasket. Start it up and check for a hissing noise by cylinder 5. It could also be a plugged injector so you could try replacing that. It MIGHT help to run some of that bottled injector cleaner crap through a tank of gas. I've never used the stuff, I always figured it was a gimmick. It could potentially be a cheap fix, but I'd wait and see what others think.
 
Thanks for your feedback J. I tried that fuel injector stuff already and I as well believe that is a gimic or just a bandaid solution to a bigger problem to come. No hissing noise but i am going to try replacing the injectors is the cost is not too high. Thanks again for your help. :) Michelle
 
michellebuck76 said:
Thanks for your feedback J. I tried that fuel injector stuff already and I as well believe that is a gimic or just a bandaid solution to a bigger problem to come. No hissing noise but i am going to try replacing the injectors is the cost is not too high. Thanks again for your help. :) Michelle
Click to expand...
Before you buy new injectors, switch the one off of cylinder 5 with cylinder 3. If the misfire changes to cylinder 3, you know it's the injector. If not, move on to the next possibility. From personal experience, I know it can get real expensive chasing down a misfire.
 
Um, guys, this thread is 3 years old and the OP hasn't been on since 04-26-09. I would think she figured it out by now :th_laugh-lol3:
 


It helps people like me who currently has the exact same problem and i am currently going through the steps suggested here to try and resolve the problem. Currently i have replaced the plugs and wires but no fix yet. I will try to update what the final solution turns out to be.
 
I've just had this happen to me yesterday, my car was fine in the morning but running sick as a dog in the afternoon. Flipped the hood and there is oil all over the front of the engine; looks like the valve cover gasket has gone again! Threw the P0305 code cylinder 5 misfire. Have ordered plugs and leads and a replacement coil,( just in case), and I've already got a spare gasket. Is there anything else I should look for, only being in the UK parts take forever to arrive here?

Plugs and leads already on the car look original, so I'm changing those anyway. The car is a 1998 Grand Prix GT. Also threw a code for the Crank Pos Sensor, as the tacho stopped working and the Traction Off light came on.
 
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