freebird01

I posted this in general maintenance but not quite sure where it fits in... I have done countless research and yes, i have used the "search" button to no avail! i have the p0300 code every day, I have a cammed 01 ws6 with 143xxx miles and has larger injectors, 255 fuel pump, new filter, hotwire fuel pump re-wire, brand spanking new AC Delco spark plugs (25 miles) wires are new, coils all tested good. the cam spec is 224/224 563/563 114 lsa thunder racing, with titanium retainers and 7.4" pushrods. it has been tuned by the previous owner at a shop called PBJ (performance by Joe) <sounds like a sketchy shop>.... Anyways on my 5 hour ride home from iowa where i had bought the car it felt like it hit a brick wall and the SES light starts blinking, I stop the car check under the hood and see if something came loose and nothing seems out of place. It seems like its random when it happens hence the p0300 random misfire but what it feels like is if im on the highway at a constant speed (i work 26 miles away from my house and all highway) it will happen. it seems like if im accelerating part throttle it will go no where until i get half pedal and then it jerks and feels like its running correct. I have tested everything from compression (190 all across the cylinders except #8 which was 175psi) i replaced the spark plugs and even checked the gapping on the old ones and they were ALL different, one was even touching the electrode WTF! i tested fuel pressure at idle and that was 75 psi, tested each injectore and they all dropped 30psi when energized. i had 2 vacuum leaks which were the pcv hose into the intake, and the pcv in the back of the engine that crosses over from bank 1 to bank 2 with that rubber Y. I fixed those and then checked my Fuel trims and if i remember correct they were close to -4% bank 1 and 19% bank 2 (these are LTFT) but dont quote me on that, before the vacuum leaks were fixed it was +55 on 1 and +35 on 2! I fixed the vacuum leak and did a Fuel trim reset and drove 40 miles home and no lights came on, this morning i went to work got 20 miles from home and the SES light started blinking and the part throttle no accel started acting up again! Im stuck!!! HELP ME PLEASE, im running out of things to test, im not sure if the person that tuned the car didnt tune it right and forgot to change the misfire sensitivity table or what, i am at a loss! I forgot to mention that the car drives just fine and there is no loss of power or even seems like it is missing if the SES light comes on and doesnt blink, just when it blinks is when there is no acceleration.dumI have screen shots of my scan tool from diagnostic data if there is any more information you need (iat at idle, maf Voltage/g ETC)

Sail Hatan

Ive been getting the same code since my cam swap a few days ago. from what I understand, its an easy fix, just needs a little more fine tuning. my tune still needs some adjustment.

Sail Hatan

but- mine runs ok, so it might be different.

2xLS1

iTrader: (25)

n/m. Went back and read the whole book.

sicksspeed

iTrader: (2)

I would be a little curious about those compresion numbers. At this point I would do a leakdown test to compare cylinders. Much more comprehensive test.

Slowhawk

iTrader: (12)

It's not the tune if it does it sometime. The car starts to run bad which tells me it is a sensor somewhere. I would probly bet on a bad mass air meter.

freebird01

Cylinder leak down test was good as well, I'm hoping its a maf because its cheaper than a new tune. Im not really sure if this has anything to do with it but i got a few readings from my scan tool

Ltft bank 2 -1.5
Ltft bank 1 8.59
Map 38kpa
Iat 18°c
Coolant 79°c
Cam signal low- xxxx
Cam signal high- xxxx
Maf 7 g/s
Iac position 54
The weather was about 16°f i have no clue how to change the settings on my otc scan tool to English units rather than metric

Old Geezer

iTrader: (3)

" i tested fuel pressure at idle and that was 75 psi,"

For starters, I'D be looking at why the fuel psi is 75....Bad gauge, or???

freebird01

i thought that as well so i tried 3 different gauges and each one was right on the money. it has a walbarro 255 and the fbody fuel pump re-wire to get more voltage.

freebird01

one other thing, i have noticed that my volt meter in the dash says im not fully charging while driving (13.2-13.6v) and about 12.8-13v at idle with no loads on. battery could be shot?

gagliano7

Is there regulator for your fuel pressure? i am not sure how your car is setup but the pressure should be 58 psi.

anheuserbusch08

iTrader: (11)

lol jk but yeah its minor tweaking on the tune

freebird01

I just bought the car 2 weeks ago, i haven't seen a regulator so my safe bet is no. I'm curious as to what the negatives are of having high fuel pressure? I'm more worried about the random misfire

Slowhawk

iTrader: (12)

75psi of fuel pressure would be a problem.

freebird01

what would cause such high fuel pressure? i guess i just overlooked that

sicksspeed

iTrader: (2)

If you could get a snapshot when the problem occurs of the short term trim it might help shed light. Being the problem is intermittent. And maybe get a base line on the sensors in question while it runs well. That is if I understand correct that it runs fine some times.

sicksspeed

iTrader: (2)

Also I don't see maf when long term is add on one bank and remove on the other. Unless that changes under the failure. Like both go real lean and grams are steady or drop.

Old Geezer

iTrader: (3)

Out running the regulator...

freebird01

Yea it drives like a champ 90% of the time but then all of a sudden it starts happening and lasts for maybe 2 min then it drives fine again. Today for instance started my car at 5:30am to warm it up, left the house at 6 28 mile drive to work and no problem... Temp was 28°f outside, no check engine light. My o2 sensor bank 1 upstream 460mv, bank 2 upstream 950mv all the wart to work...normal? Status in open loop while way to work.

freebird01

Fuel trims while way to work were 0% lt and st both banks