Stock '06 5.3 with MP70. A little history....Ran great on blackbear baseline tune when first put together. Idled, part throttle, boost, whatever, ran almost perfect BUT was lean in boost so logged a couple drives and sent to BB, he said my MAF wasn't working properly, so he couldn't update the tune. At this point the MAF was right on the throttle body, so the air was going through a 90/expander.

Cleaned MAF, still ran great, logged data, sent it to BB, he said MAF still no good, try different placement.

Put MAF in straight section of charge pipe, about 8" after BOV. Truck ran terrible, erratic idle, lose power/die at any rpm, boost, no boost, etc.

Bought a new MAF, put it in, didn't idle worth a ****, still cuts out randomly when driving, doesn't matter if in or out of boost, etc. Nothing about this truck runs good.

Anyway, I pulled the MAF plug to check the connection, and voila, truck runs PERFECT. Took it for a drive, and the damn thing drives like it came off the factory floor. I didn't get beyond maybe 1psi boost because AFR was at 14-15the whole time.

Is this normal? I don't know what to do with this thing, it's driving me nuts. I know you will all say go speed density but I paid to have a flashscan tune done, and I KNOW it can be tuned with the MAF. Any help much appreciated.

 

When you unplug the MAF it defaults to speed density. But, unless you have a 2bar MAP it cant calculate past atmospheric pressure since stock is 1bar.

Basically I would just have him do a speed density tune on it, just make sure buy a 2bar MAP if you go that route.



You have to do this when doing an induction service. Take the intake off, unplug the MAF and it will let it idle normal instead as if there is a huge vaccum leak.

 

I'm really tempted to unplug mine until I get the MAF tables tuned properly. Did unplugging it give any codes or DIC warnings?

 

Whatever any of you do, DO NOT GO INTO BOOST with the maf unplugged unless you are 2barSD.

 

If you go WO with it unplugged we will be reading about you needed a MAF and Motor.

 

Ya I figured that, that's why I never pushed it at all. As for DTC's I'm not sure, I wasn't logging at the time. The check engine light was on but it's been on the whole time since I disconnected the egr.

 

What if you had the 2bar MAP, but weren't tuned for SD, just unplugged the MAF? Would the VE tables adjust based on manifold pressure?

 

Nope.

 

No it will not, actually it would be even worse. Hard to explain, if you go 2bar you will understand once you do.

You have to have a 2bar MAP and it HAS to be tuned.

 

If you put a 2bar MAP on but dont tune it, how can the stock PCM know it can read up to 2bar now?