dreww

iTrader: (1)

I have had this problem since I did intake and heads on my corvette.

It backfires when, say, cruising to a red light and you let off the throttle and the rpms are above 2500 when you let off. It would sometimes do it just sitting at the light in neutral (6spd) and pow! outta no where. sounds like a gun shot or something.

I put in 42lb injectors and it did seem to help the problem, cutting down on occurances about 50%. Ive been told its a timing issue....but too much or too little?

I have hptuners and am decent with it....where should I be looking to adjust this issue? or anyone have any ideas what else could be causing it beside timing. Other than this, the car is heavily modded and runs great and strong.

watman02

iTrader: (9)

im assuming u adjusted the tune after the heads adn intake?
do u have a WB what does it say when this happens? what kind of timing are you running at idle? bad gas?

dreww

iTrader: (1)

I had it dyno tuned by a great tuner here in d/fw. But I did not get it retuned after the heads and intake. It literally fired right up and ran great (minus the backfire) on the first try of starting it.

I do have an apiller wideband gauge setup in the car. Ive never looked at it right as it backfired, but the numbers seem normal as soon as I glance at the gauge after it backfires.

At wot, if it matters, I don't get backfiring when letting off the gas and it runs fairly rich at wot. low 11's. but I realize a lot of that doesn't matter when not in PE mode.

my timing is set very high at idle....I would have to look to get exact numbers on my tune but high 30s. I heard a big cam will require such numbers and the timing hasn't been touched since the "professional" tuner worked on it before the heads and intake.

btw, thanks for responding to my thread.

watman02

iTrader: (9)

are you still running the maf? try lowering your spark at idle as it will give more control for surging as well as maybe help the back fire. also your transisent fueling would be off due to you changing heads and intake the VE is now different.
are you F/I? why are you running low 11's for afr when wot??? im running 13.0 afr?

dreww

iTrader: (1)

I am still using the maf, yes.

thank you for the recommendation. Should I reduce timing from idle to say, 2500 rpms?

I do run nitrous on this vehicle, so I would prefer being a little more rich than lean. I also didn't want to mess with PE AFR ranges until I get this little problem under control.

watman02

iTrader: (9)

I would just reduce it at the cells u idle at and blend it in.