Thread: p0300 random misfires

ok so i just had a p0300 come up random misfires and no other codes

i looked at misfire history this is what it shows

cyl 1) 0
cyl 2) 0
cyl 3) 81
cyl 4) 655
cyl 5) 4
cyl 6) 2

So i do know i had some from cyl 2 4 6 cus i forgot to plug in my injectors when i painted my fuel rails but i cleared those when i tuned the car with hp tuners.And it apparently worked cus there are none on 2 so the ones on 4 and 6 must be recent.

I am running rich though. My o2 b1s1 was reading up to 1045 at wot. So could i of started to foul my plugs i recently changed about 2k ago?
My ltft were all within -4.
I have 0 kr.

I did notice awhile ago when i took off my ecm that it was pretty beat up so im thinking that could also be an issue.

I did my lim and plenum and coolant elbows about 1k ago and torqued them to specs but i didnt put anything on them so is it possible they loosened?
My vac seems to be good though at 19-22 at idle.

Also i changed out my therm for a 180 and tuned it for it and noticed yesterday my coolant res was low and i could hear the coolant like flow through from inside the car like there was air in it so i threw in some coolant today.

Also another thing to note i took off the protective metal sleeves on the plug boots when i changed the plugs the last time cus i heard they have been known to cause issues and never put on different sleeves.

I did get gas at this random station yesterday and filled from empty so i have no idea the quality of the gas soo who knows.

Its possible too much fuel as fouled those plugs. I would be using a wideband if trying to tune.


I would also pull those plugs with the misfires and see how they look. You could also try swapping the coil around and see if the cylinder with the most misfires follows.

Originally Posted by Fivefingerdeathpunch

Its possible too much fuel as fouled those plugs. I would be using a wideband if trying to tune.


I would also pull those plugs with the misfires and see how they look. You could also try swapping the coil around and see if the cylinder with the most misfires follows.

This is my thought.I have some tr55s almost brand new i can use if need be.
And ya i know i am going to be grabbing a wideband within the next couple months along witha 3.6 and tuning it then.

Only thought though is if i am running so rich im fouling out plugs then this is going to take a toll on my valves and pistons so im scared ima be getting some floating valves. Hopefully some seafoam will take care of this cus i dotn feel like ripping it apart to clean.

I guess ill just run a couple bottles threw it this week and then change out the plugs and this will be enough to keep it ok untill the tune cus this is my dd. Ima also have to take it easy with no wot untill then but even still when taking it easy i have seen the o2 fluctuate past 1k

During normal driving you wont have an issue with too much fuel, only at WOT will over fueling be an issue.

It can foul plugs, wash out the cylinder walls (the oil) and make the car slower.

You wont see valve float because of too much fuel, valve float would be a concern if you were highly modded and running the incorrect valvetrain mods.

Maybe try un-doing some of the stuff you did to the tune, go back and look over things that you may have missed. Make sure that when you do change a number for say MAF, fuel, timing, power enrichment that you know what it may do to something else in the tune.

Originally Posted by Fivefingerdeathpunch

During normal driving you wont have an issue with too much fuel, only at WOT will over fueling be an issue.

It can foul plugs, wash out the cylinder walls (the oil) and make the car slower.

You wont see valve float because of too much fuel, valve float would be a concern if you were highly modded and running the incorrect valvetrain mods.

Maybe try un-doing some of the stuff you did to the tune, go back and look over things that you may have missed. Make sure that when you do change a number for say MAF, fuel, timing, power enrichment that you know what it may do to something else in the tune.

Unfortunately Ima have to suck it up until i get that stuff cus i gave bill back his hpt. I was just thinking that it may cause excess carbon build up. How can i post my .hpt file for my tune and scan on here?