My LB9 is running a $6e chip and is a MAF car with Procharger. Now sometimes the car will run lean under power - 18AFR on the wideband. At 1/2 throttle it's 14 or so then when I hit the gas hard it starts at 13 then climbs to 15/16 and then of course I let off the gas.

Yesterday I did this and seems like lack of fuel for the first 20 mins of driving. I turned the engine off for 20 secs, made sure the ECM blinked briefly, restarted and carried on the journey. Well for the next 20 mins it was perfect- 11.5 AFR under boost well up past 5000 rpm and 5lbs boost. So 2nd half of journey the car is perfect, the first half not great.

I am wondering if for the first half, the ECM wasn't communicating properly or if I need a 3 wire 02? I have ceramic headers so I do wonder if that s my problem?

Any thoughts or advice? I would really use some help here. To be honest if you provide the answer to this I will paypal you $10 usd for your time. It's been worrying me for some time..

The car is almost perfect.... just need this sorted.

 

Whats the coolant temp when this lean issue is occurring? What does the battery volts show?

 

MAF wire clean?

 

Orr- voltage stays around normal 13/14 volts and temp is around 160. Mind you that is from the gauges and not data logging.

TTOP- Would the MAF wire only affect when cold? When warm its all good.. I did put on a new old stock MAF a few months back. I also have new relays for MAF burn off (though mine are only 2/3 years old)

 

If its in closed loop during the cold run lean out, i am not sure whats goin on there.
I was thinkng if it does this with cold engine water temps during warm up, it may need more open loop vs coolant temp correction

 

I'm just throwing baloney at the wall to see if it sticks but oddly enough, I just replaced a maf that was doing the exact same thing..
However, with a maf that's fairly new, chances of that failure are fairly slim.
I'd say the best thing would be to log it to see whats going on if you can.

 

Thanks Fellas. The MAF was old stock so could need a real good clean or something?