High LTFT at idle..

[50thzo6]

Hey, thanks for looking at this, any help is appreciated.

My car is a 2003 zo6, with GM asa cam, a&a kit with 60lbs injectors, kooks exhaust, Racetronics in-tank pump. The car was dyno tuned and made good power by a trusted person in my town a couple of years ago. I don't drive this car very much and a couple of weeks ago I changed the oil and it has a strong smell of gas. It has always smelled very rich when standing behind the car but I never thought twice about it. Well after the oil change I decided to hook up the hpt and scan it. After starting the car in the garage with in 2 minutes the LTFT go positive 25 on both banks. That explains the rich condition or lean however you want to look at it. I thought why would the car think its lean? vacuum leak? I smoked the intake and found no leaks, got 2 new Denso O2 sensors. The car has no cats or rear O2s. A new GM MAF, checked fuel pressure 58 psi, replaced the header gaskets, replaced the intake gaskets, checked the vac port on the back of the intake. I have a breather on the pass. valvecover and vac plugs on the ports and on the TB. My check valve is good on the brake booster and the A&A supplied one that goes to the valley plate is good too. Yesterday I drove the car around the block and it runs great and after it got up to temp I let it idle and sure as shit the LTFT go to 25+. So I think the source of the problem is in the tune. I don't know shit, but this is my guess. Again, thanks for your help.


2003 Chevrolet Corvette Z06 - DTM - Carl Gentile.hpt
very rich new maf.hpl

Carl

[blindsquirrel]

Gas-in-oil can be both the cause and symptom of a rich condition... usually rather tricky to figure out which is which. It can take several oil changes to get rid of the fuel in the crankcase, and if it's a over-fueling issue it keeps getting contaminated the more you run it for diagnosis.

I didn't look at the tune/log, just wanted to give a generic warning to let you know it's possible to end up chasing your tail around in circles when this happens.

[kevin87turbot]

It's very likely that the issue is in the tune. If you use the scanner to command open loop, does it run poorly?

[50thzo6]

When I go to "fuel" under "controls and special functuons" there is command closed loop, on or off. When I select the off button the idle does drop a little but it still smells very rich out of the tail pipe.

[kevin87turbot]

I suspected it would drop the idle a bit. It probably drops the manifold vacuum as well.
That tells me that it really needs that extra fuel.
It's going to smell rich with that ASA cam and no cats. There's just no way to eliminate the rich smell. You can tweak the injector timing just a bit, and that will help, but it will still have a strong rich odor.

[50thzo6]

Dang man, I was really hoping to get a handle on this. You think this is just a charastic of the cam?

[kevin87turbot]

Dang man, I was really hoping to get a handle on this. You think this is just a charastic of the cam?

I suspect it just needs to calibrated. Just DM me if you need help getting it dialed in.