Po300 random misfire is back

[ssms5411]

Like title says random misfire is back, hard to start also, have to give it gas when cranking it over to start for about 2 years now, thought it was something else so been trying to narrow it down. So I ordered a new Maf to see if thats the problem. Also ordered ZZP coils to try them out. Im going to spend tomorrow trying stuff out but all of the other sensors have been replaced so Im at a loss.

[2.8 Bird]

You don't have bad or dirty injectors or maybe even a vacuum leak somewhere.

[ssms5411]

Don't know been looking around, replaced a coil yesterday but didn't resolve my issue. Will check today.

[ssms5411]

Checked everything out, couldn't find anything, when I take into the shop tomorrow morning, ill have them check it out. Maybe they have better scanners than i do.

[ssms5411]

Got to the shop and on the way there floored it and got a blinking ses light when they checked it , it was just a dtc300 so can't tell what it is. Ran fine up the mountain coming home but I didn't floor it . Got home checked it with the hptuners and dtc300 and dtc303 show up. I think next month ill take it to the dealership and see what they can tell me.

[ssms5411]

Got the new maf in, no change. Got the ZZP coils look great, waiting on the icm then Ill install all at once.

[ssms5411]

Since im getting the dtc300 and 303, changed the plug on cylinder 3, put on new wire ,already swapped coils, ill do the zzperformance coils and ICM this next week then its off to the dealership.

[ssms5411]

Got the new icm and zzp coils in, only bad thing about the coils is their not slotted to run the wires to the drivers side so you have to pull them around so their facing the passenger side. No change, still getting misfire code. Car runs great. So maybe crank sensor or fuel injector. Taking it to the chevy dealership next month.

[ssms5411]

Used a stethoscope on #3 injector and its firing so this next month I'll have the crankshaft sensor replaced. Then go from there. Can't be too much more to replace, might have them do a compression check also. Also ordered a new harmonic balancer, figure its 13 years old so might as well replace it while their in there. Only got 10 years out of the stock one, changed it in 2006.

[ssms5411]

Just talked to my mechanic, hes going to install my new balancer and crank sensor on the 17th this month. Only charging me $80 what a steal, but ill be working it off tuning his 4.3 truck when he starts working on it. Its a Chevy luv with a 00' 4.3 engine. Hes making it pretty wild.

[ssms5411]

Got the new balancer and crank sensor in still missing. Crank sensor had some metal shavings on it, but not bad. My mechanic thinks its the injectors, only thing thats left to cause a misfire. Only charged me $50, so that was good. So Im going to get some new 60lb injectors, they dont sell the Motron 65lb injectors anymore, so have to go with the Siemens ev1 60lb. Ill try and get them next month.

[ssms5411]

Also its a little better so far no blinking ses light when I rev it to 3000 rpms or more so thats different, just the dtc 300 in pending codes, so its getting better. The crank sensor was original so it had 172,000 miles on it so I'm glad it was replaced. Been adding seafoam past few days so if its a clogged injector maybe it will help. Probably drive it this week to see if the seafoam works, also need to replace the idler pulley, its making noise my mechanic said. So ill replace that this next week.

[FirebirdGT]

... also need to replace the idler pulley, its making noise my mechanic said. So ill replace that this next week.

Do you still have the original plastics pulleys or have you upgraded to the 98+ metal ones before?

[ssms5411]

Do you still have the original plastics pulleys or have you upgraded to the 98+ metal ones before?

Their the metal ones.

[ssms5411]

Took it out yesterday for about 60 miles , ran good , got on it a few times ,no blinking ses light so I would assume the crank sensor was causing it, still get a pending code of the PO300 but now Im thinking my cam and 1.7 rockers could cause a false PO300, since ZZP says in their description that prolong idle will cause a PO300. Going to run some more Seafoam through it, ran 6 cans on one tank. They say dont go above a 50% ratio. Ordered another 6 cans so Ill run that also. Should clean it out pretty good.