Weird Missfire Problem

[dvd50l]

ok guys i need a bit of help, a bit of a brainstorm i guess and any help would be appreciated.

for the last few weeks i have been doing a few little modifications to my series 2 33gtst including 100 thousand service, new plugs gapped to 0.8mm, bosch 040 fuel pump, front mount intercooler, new plazmaman intake plenum and throttle body and a power fc which all needs to be tuned.

now heres where my problem is, on really cold mornings, like freezing cold morning, it has a missfire at idle and through the entire rev range, continues like this till it has reached just over operating temp and seems to clear itself and runs fine there after, now its not just when the engine is cold as if i leave the car sit all day and start it again in the arvo it doesnt do it.

so far i have tracked it down to be on number 1 cylinder and will be doing some more tests in the morning when i get back to work, so just wondering if anyone has had this prob or heard of it before, is it a tune issue, bad plug coil pack etc, any help or suggestions would be mostly appreciated.

thanks

[mad082]

at a guess, it is going to be a spark or fuel issue (such as AFR's being out). it will be caused by the cold, dense air in the morning, and that is why it won't do it in the afternoon. and the reason why it stops as the car warms up is because the heat from the engine is warming the air up.

if you are only running the basic tune that was on the pfc then that is probably going to be more of the cause than anything. it isn't recommended to run on this tune for long. if the tune on the pfc was done before the bigger throttle body and plenum that that will be the issue. it will probably be running lean (cold air is more dense, so it needs more fuel to achieve the correct AFR)

[dvd50l]

thanks for the reply mate, yeah the pfc is only the basic tune i only been driving it to work and back so like 20 k's a day for a few days

an update on the situation

got to work this morning and changed no 1 and 2 coilpacks around, missfire still on no 1 cylinder

then changed no 1 and 2 spark plugs around and still missfire on no 1 cylinder

then lastly i put my noid light on no 1 injector and nothing, no flashing, tried on no 2 injector plug and it was flashing, so back on to no 1 and nothing

so the cause of the missfire, or running on 5 cylinders is due to no injector pulse on no 1 injector.......but why i still dont know

so te next step tommorrow morning is to swap the pfc for the standard ecu and see if the problem still occurs, if it does then i beleive i have a wiring issue somewhere, and if it fixes the problem then there is something wrong with the pfc/tune etc

has anyone else ever had or heard of this problem???????

[700HP-GTR33]

it may be your injector.

But $100 bucks says it is either your resistor pack or your cables to the coil pack.

[Bmboy]

Our neighbour's Holden Missfires on cold starts, i remember chatting to him (because he works with those cr@p-mobiles) and he said it was either the distributer playing up or slack in the timing belt or chain - (which makes sense because if you have slack in the fan belt, the sound goes away after about 2 mins of running - or until you re-tension it).

[dvd50l]

hey guys thanks for all those that had some suggestions for me, i found my problem this morning, so here is what was wrong

***The Connection To The ECU Was Bad***

and thats all it was, seems i had a case of a slightly banana like plug and wasnt making good contact on te lower pins of the ecu which just happen to be the pins that pulse the injectors. GAHHHHHH

so after all that it was a simple fix i simple just pushed the connector on properly and now runs sweet as

so just a little heads up to anyone that ever has a wierd problem like this one, check the connection to your ecu, especially if like me you have been playing round there lately