daddydec21

Hello new here to the forum. I am haveing po300 problems. started off as a cyl 1 and 2 misfire, replaced coil, plugs, wires, cap and rotor (acdelco), maf, tps, distributor, checked for vaccum leak by spraying every inch of the motor, cyl 1 was misfireing at 96 misfires per cycle and cyl 2 was 79 misfires per cycle, now i have a cyl 3 misfire at 185 per cycle, checked fuel have 64 psi with key on and 55-60 with it running, also did a injector test and all the injector pressure to 65 and go to 30psi t the same time, replaced with new cam sensor, new egr reading on my scanner at 1500rpms my cam would go to -17 degrees so i resat the timing at 0 degrees and it seems to running a little worse. Starts with no trouble but has a small rumble seems like it has a radical cam , If you go to pull out i stumbles a bit but runs fine with higher rpm. misfire counter goes down between 20 and 65 at higher rpms
check engine light flashes unless i am on the gas at around 12 1300 rpms and higher



here the specs from my scanner,.

rpm 700
tps 0.57
b1s1 495-600 MV fluctuates constantly
B2B1 200-550 MV fluctuates constantly
B1S3 200-740 MV fluctuates constantly
A/F RATIO IS 14.7
MAF 7.5
BARO (KPA) 95
MAP 2.05 V 49(KPA)
COOLANT 94DEG CELSIUS
INTAKE AIR 16 DEG CELSIUS 2.66V
IAC 84
DESIRED IAC 84
DESIRED IDLE 650
IGNITION 13.5 VOLTS
MISFIRE CYL 3 184 PER CYCLE
KNOCK 4.65
SPARK ADVANCED 22
KNOCK RETARD IS 0
CAM RETARD 0
CAM RETARD CHANGES TO -17 AROUND 1300 RPMS AND SLIGHT TO NO MISFIRES AFTER 1200 RPMS
B2S1 SWITCHING FROM LEAN TO RICH CONSTANTLY
egr 0.76

kevinkpk

I'd suggest set the timming to what it should be, and give it a hefty dose of injector cleaner or sea foam

daddydec21

an specific way to do that. that works the best?

kevinkpk

Is this not just an hei distributor?

daddydec21

vortec plug wires come out the side of the cap not in the top

daddydec21

ok so after ripping everything apart i come to find someone changed the spyder already........... took it to a local shop they cleaned it n tested it it was fine put it in and still same thing cyl 3 misfire?????????? what next

bat man1950

po300 tps over fuel ing I did alot of what u did oz sensers a lot of thangs cel on when idle or when u let up on gas when I step onit it when flash ing it went out

engine55

Look at the posts inside your distributor cap. If you see signs of excessive arcing you have a problem with the gears at the bottom of your distributor. It’s a common problem in high mileage Vortec engines. It always leads to random misfires. Go to www.vortecrighttime.com and get their rotor. They guarantee it will fix random misfires permanently. I had the same problems with my last two Vortec equipped vehicles. The new rotor completely fixed it. I got a new distributor. It worked for about 6 months and the misfires came back even worse.