Stock 2003 lq9 - idle closed loop idle ltft high at 25%

[joe1936chevy]

Stock lq9.. only differences is speed density (unplugged maf)

Also, I am using a different set of manifolds, as well as using a gen 4 tps with an xlink adapter and straight pipes.

I have no evap stuff set up, no leaks that I know of. Left codes on for missing evap.

Car runs pretty good open loop, pretty good closed loop, but the long term fuel is up to 25%

I haven't touched the tune too much, other than VATS and a 4080e segment swap.

I'm thinking the 02 sensors are reading too lean because of aftermarket manifolds, but I really don't know.

Long idle is the simplest attachment showing it. Also attached a mini street drive too.

[5FDP]

What's your fuel pressure?

Is the MAF failed correctly in the tune?

[joe1936chevy]

Maf is unplugged. I thought that was enough to force speed density. Fuel pressure stays constant and it?s in stock return

[5FDP]

Stays constant but at what pressure?

Needs to be 58psi give or take.

You still have to actually fail the MAF if you want to tune in speed density. Set the MAF fail high to 0hz and set all 3 MAF dtc's to MIL on first error.

[85K5Jake]

Is it a truck maf with the built in IAT sensor? If it is plug it back in you need the IAT and fail it like 5FDP said.

[joe1936chevy]

I separated the iat sensor wires and put it in a new hole in the intake as a separate sensor. So my maf and iat are separate

[joe1936chevy]

Properly applied those MAF settings (tuned them out). Fuel injectors are good, working on getting an actual fuel pressure gauge. It's as if, on cranking, it first runs okay, and after a few seconds you can see where the O2s read as lean, so the computer keeps adding fuel, and adding fuel, and the O2s may blip as being rich, but it reads as lean. I turned the car off and on again, with the O2s hot, and same issue - they read in the middle for the first few seconds, then they read lean, and the computer constantly creeps up. Checked for vacuum leaks and found none, happens through the cells up through 1500 which helps rule out a vacuum leak. I'm off to try a fuel pressure gauge but I'm doubtful, as I've had no other symptoms of a weak pump.. it's brand new, and this is idle, and it's the stock return system.

[5FDP]

Post up your tune file.

[joe1936chevy]

Tunefile attached

[joe1936chevy]

Turned out it was too little and too old gas. Runs much better. Still rich on idle, but I can smooth that out in ve