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JAH11's 1968 GTO

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Newbie from MD in need of y'all's expertise

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Hello Forever Pontiac peeps, and thanks for letting me hang out and hopefully be able to keep my 99' Grand Am GT coupe for years to come. I figured if you guys and gals can't help me get this thing running again, I'm donating it to Goodwill.  I was in need of transportation FAST, and my father in law graced us with this beast for what he paid for it. $350. So you could imagine it needed work. Fast forward to last October ( have had it for like 5 months now). So I'm gonna go through what happened, and where I'm at right now. Car was running hot and no heat inside, straight cold air. Replaced water pump, thermostat and installed flush kit for coolant system. Didn't do a darn thing. So I had to run it with coolant fill cap OFF just kept a lot of 50/50 mix in the car. Drove it that way for 2 months or so. This past January one Saturday I was taking my step son to his grandma's house driving it like I had been. We'll I stopped and filled coolant up in the Dollar Store parking lot, and proceeded into Rouzerville PA up the mountains. It started losing power at the pedal, like it was bucking. I notice my speed had declined FAST, and temp was spiking into the red. Immediatly pulled into someone's driveway and shut it off. That was the last time the car ran. It sat there for almost a month until I could tow it home. We'll I've been going through a process of elimination since early March up to yesterday, and I'm stumped. The first thing I thought was plugged Cat, so to check that I pulled in out ole faithful and saw called 2 cut in the exhaust pipe about 3-5in.  in front of converter. Oh I forgotten to mention that while I was driving the car like I was, it threw a DTC P0300 Mutiple misfire. The scanner suggested replacing the Evap Purge valve selnoid? I told the scanner it was nuts and drove it anyways. So back to the vents I cut in front of cats, didn't do a darn thing. All the car does it crank and crank and every so often backfire, but won't start. So it's sits right outside my bedroom window, like a jilted ex love longing for companionship. So this is what I've done within the last two weeks, and still no start. Replaced EGR Solenoid 2 weeks ago, no change. Checked for spark and got lit up in all 6 cyclinders. Plenty of fuel as well at the rail when you press the bledder valve. Got a few wild hairs within the last 3 days, so went to the salvage yard and found a few really nice 3.4l and started strip mining emission parts. Replaced all 6 plugs and wires. Replaced Coolant Temp sensor. Replaced MAF sensor. Replaced both the IAC and TPS. Replaced fuel pressure regulator. Replaced MAP sensor. Replaced Evap Purge valve selnoid. I was expecting something to happen but was so disappointed yesterday when I tried starting, and no change what so ever. I don't have the tools to test the cylinder pressure, but the RPM does move on the scan tool when cranking engine over. I didn't change either O2 sensor, but did unplug them with no change. I needed HELP PLEASE. The only thing I haven't messed with is Evap charcoal canister. Fuel cap is tight, and yes I put 2 gallons of fresh gas in it yesterday. Sorry I wrote A novel, but didn't know how else to explain everything I've tried. Thank God I have another car. Now this Pontiac has turned into a mission. Any and ALL advice and suggestions will be most appreciated. Thanks for all your time.

Dazed and really baffled on MD.

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Sorry for being late to the party. I hope you haven't junked your car yet.

First thing that comes to mind is the crank position sensor maybe shot or failed. The PCM can't tell where the crank is in relative position to the firing sequence at that point and that could explain the DTC P0300 code too.

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