baezi z06

iTrader: (2)

Hi

i´m trying to figure out some strange misfire problem in myn Corvette C5 404ci cam 248/254 615/622 114lsa

it´s brand new rebuilt motor in it only 150miles on it and i´m logging the car whith HPT and it it throwing p0300 code first after startup and then in driving it´s current misfiring on both #2 and #3 and sometimes it flashes the check light, but the funny thing the car doesn´t feel all that bad.
it seems to misfire only under little load on around 1800-2500 rpms but nothing 0 whith a bit of throttle
misfire current on #3 is showing much 10-50 and sometimes all the way up to 110-120
but
misfire current on #2 shows less from 10 to 30-40
and all the others cyl. are normal

Things i´ve checked so far
plugs OK
Wires OK
Coils OK
Swapped Coil-bracked OK
Exhaust leak OK
Injectors OK

so i´m gona do a compression test but this sounds more like some electric/ground issue to me and others here....

What could this be ? has any one else had similuar problem

Baezi

NicD

iTrader: (7)

Every cammed car will think it's misfiring unless it's adjusted for in the tune. I can assume it hasn't been professionally tuned yet?

baezi z06

iTrader: (2)

not dyno tuned, but in 1st mailorderd and then fine tuned in HPT

If that was the case, why would it only do this misfires on only these two cyl and not the other ones ???

Baezi

NicD

iTrader: (7)

Couldn't tell you without seeing the car. At least post up the tune so things can be looked over.

baezi z06

iTrader: (2)

can you read this

NicD

iTrader: (7)

Your file is locked.

Rhino79

iTrader: (7)

Misfire tables are very sensative in factory tune. I usually raise those values a good bit. Hi stall converters will cause it to do that too. I see u have a 6 speed so id just have ur tuner bump up the misfire tables if they havent been.

baezi z06

iTrader: (2)

that´s not the case here, it´s misfiring more then normal on nr. 3 and nr. 2 , it´s leaning out, the fuel cell´s are throwing more fuel because of this misfiring



could it lie in the wires (loom) bad ground or something like that....

Baezi

baezi z06

iTrader: (2)

i´ve been searchin on the forum, and on the hptuners forum and i´ve runned into few threads about case relearn , if it´s needed it can throw p0300 codes and show as misfire on some cyl.


I have changed from LS6 engine to LS2 stroker engine whith out doing case relearn
and then again i just changed the crank , new 4" in the new block when i rebuilt it

but i´ve never done case relearn.

Can this be my problem

Baezi

Slowhawk

iTrader: (12)

First thing I think of is to make sure the Cam sensor wires are correct.The car will run but misfire if the cam sensor wires are switched around. On the vette it will still read the tach unlike the f-body.

A good way to tell is that is starts fine a few times then has a problem starting.Also idle can vary and be a bitch to tune in.

JDMC5

iTrader: (3)

do a case learn it only takes a minute, I did one and it helped alot, almost cleared up all the misfires.

baezi z06

iTrader: (2)

it starts up good !!!

the cam wires/sensor is ok, and the car idels fine, just this bit misfire reading on cyl 3# and 2#

i´m gona try this crank relearn see if it does something for me

wil poste it up

Baezi

baezi z06

iTrader: (2)

CASE LEARN solved my problem

it´s not misfiring like it did ant the LTFC are on the same boat not dropping fuel here and there in they´r each direction

thanks

baezi

JDMC5

iTrader: (3)

you are welcome.