TURBHOE

iTrader: (4)

i've had this in the tuning section for awhile but i think its time to move it here.

first off specs of motor bottom to top.
stock crank with arp main studs
new oil pump from autozone.
eagle 4.3l H beam rods.
speed pro small block Chevy boost pistons, about 8.8:1 compression .30 over iirc
speed pro rings.
comp cams 224/224 525/525 110lsa
comp cams recommended push rods
summit racing lifters
felpro mls head gaskets
stock rockers
918 springs with 4.3l seats and retainers .610 coil bind IIRC
heads were port and polished by local guy and new valve seals installed
marine intake manifold (tune set for injector size)
tr5 spark plugs, new wires, rotor bug, and cap.
new crank sensor and cam sensor
i think that sums it up


now that you know the build here is the problem

it misfires like no other. can't figure out why. compression check for left bank is 145 for #6 and 150 for# 2& 4 and oil pressure is about 60psi when warm at idle. it seems high but i don't know. when it misfires it starts adding fuel sometimes which makes it worse. all spark plugs are black as coal. i finally got it to lean out yesterday but no help with misfire.

TURBHOE

iTrader: (4)

also spark plugs go black instantly. he just changed them and 15 min drive later they are black again.

hirdlej

iTrader: (31)

Did you check the spider assy to make sure all the injectors are working properly? This or the fuel pressure regulator is toast which is on the spider assy as well. 4.3's are prettu bulletproof except for the injector assy's.

TURBHOE

iTrader: (4)

with the marine intake manifold it becomes regular port fuel injected. it has normal injectors and fuel rails. but during a fuel pressure test i did when you would turn the key on fuel pressure would rise then fall right back down to zero. i thought maybe the regulator was bleeding off fuel but i pinched off the return line and it still zero'd out.

hirdlej

iTrader: (31)

Sounds like you got a leaky injector then that isn't closing properly. It's leaking somewhere.

hog

If you clamed off the return line and it still leaks down to ZERO, then youve got a leaky injector or a fuel pump that is allowing fuel back to the tank.

That injector balance test would tell you this issue in a few moments.
Many scan tools can do this test.

Were these new injectors? I installed used EV6 stainless tip injectors that were used, but I had them cleaned and flow tested.

My fuel pressure with may marine intake does bleed down to about 25 psi, but not down to zero, sounds like you have injector issues.

Bad injectors can casue missfires and an injector that dumps fuel will foul plugs.

peace
Hog

stock48

iTrader: (16)

Could you have mixed up the injector wiring when doing the conversion?

TURBHOE

iTrader: (4)

we pulled the injectors out and could see any leaking. i know the injector test would be ideal but the guy don't really want to spend the money on it. i think on pay day he will be buying the new injectors and pigtails. the injectors came with the manifold but they were installed already. we checked the wireing many times. when i installed the pigtails i went by the plug arangement on the factory harness. then we verified with a few write ups we found from here and syty.net.

one thing i haven't changed in the tune was min pulse width. but that should hurt WOT. and it misfires all the way up the rpm range. the cel flashes and everything. he checked the right bank today with 140psi across the board on the compression test. i still don't know how this compares to other 4.3's with low compression and cams.

question, how much will a compression test change (psi) from doing it with tb closed to doing it wot. i had a brain fart and didn't hold the throttle open. and i forgot to tell him today to do it that way. i don't do these everyday lol.

hog

I'm hoping a set of injectors will help you.

peace
Hog

TURBHOE

iTrader: (4)

ME TOO!!! but if not what do you think of my funny map readings? this thing reads 60kpa at idle and about .25 throttle it reads 80-85 kpa and not even half throttle give 100kpa. but yet the brakes work like normal. i need to put a vac gauge on it to see where it idles at. does this sound like a leaky map sensor or just a big cam?

it might be worth mentioning i disconnected the maf and it ran a ton better. this is my maf off my truck so its good. his maf got wet and it really ran bad.