Zulufoxtrot

Just finished putting on my ported 243 heads and ls6 intake and 42lb injectors and when I start it up it stays at about 300rpms and does not react to throttle at all unless held constantly engine also shakes quite a bit I'm just wondering if it's normal since I just added all these thing to it and haven't gotten it tuned yet it will also bounce around in roms a lot if I leave it idling for a while anyone got an idea or do I just need a tune no codes are being thrown up

Mercier

iTrader: (15)

Theoretically just increasing airflow with the intake and heads might not have upset things completely as the MAF would see more air and attempt to compensate. Of course by the injectors obviously you knew you would need more fuel under load; but it might have been able to settle down to a half-*** idle. But injector flow is one of those values that the PCM relies heavily on to know how much fuel it is dumping in there. If you could run it long enough without causing further issues, you would eventually get codes I think.

Short version: if you change injectors, it will not be able to compensate and run even decently until you get it tuned. The PCM still thinks it has stock injectors and will until a tune.

Zulufoxtrot

So the bigger injectors could cause the shaking problem since the ecm doesn't know what to do

Mercier

iTrader: (15)

Yes, among other things. It will at least run very rich. Did you do all that and not change the cam?

Zulufoxtrot

Yeah I didn't change the cam decided to get the heads first and do the cam later I'm going tomorrow to get it tuned so I'll find out what's up then and post the after effects of the tune

so I got it tuned runs great now it was due to the injectors being different car is much faster now don't know by how much but it's noticeable