Drivability issue Eclipse (stall)

2004 Mitsubishi Eclipse Rs 2.4L

History
Car was not running September through the end of March. (Crank no start) Fixed short to ground on MFI circuit.

Going to change the Valve cover and plug wells gasket due to oil in plug wells.

The car runs fine cold but when it warms up it starts to bog down. Here is where I am at.

At idle 02 sensor sits pretty high at .9xx but does oscillate. I did several tests and have concluded the 02 is actually working and isn’t the cause of the problem.

At Idle Fuel trims are high positive up to 24 and look normal at higher rpms with open throttle. It’s behaving like a vacuum leak. But it isn’t a vacuum leak which I’ve checked for.

Fuel delivery is is within spec.

The MAF sensor is giving me concern. Whenever the car bogs down, I notice the lb/s drops off my scan tool right when the car is bogging down. It’s only completed stalled once.
The MAF looks really clean.

I disconnected the MAF and the car stops bogging down and runs fine.

I’m about ready to make the call on the MAF.

I haven’t tested injectors.

I’m going to test the MAF for voltage tomorrow.

Am I going in the right direction? And how do I make the 100% call that it is a bad MAF?

The fact that the engine is running btter w/o the MAF is a strong pointer...

Anyhow, you may want to record some parameters like rpm, maf and load with your scanner while test driving. Then put these pids into a volumetric efficiency (VE) calculator and check the results for rationality.

Read earlier topic "O2's reading lean. Wiring problem?" Focus at the end of topic.

That could be complementary to juergen suggestion to check MAF sensor.

The 02 is actually reading rich. But my fuel trims are behaving like a lean condition. I’ve verified the 02 is fine and that the wiring is fine on that circuit.

I’m thinking I have 2 problems.
Every time the car stalls the MAF shows a correlation by dropping off my meter.

And I’m thinking the rich reading on the 02 maybe just a tank of bad gas or a leaking injector given that the vehicle has sat without running for a long time.

It’s weird the fuel trims suggest lean and 02 is reaching rich.

John Curtis wrote: It’s weird the fuel trims suggest lean and 02 is reaching rich.

Agreed. You're sure the vehicle is in closed loop when the O2 reads 900mV and the trims are pegged?

Have a look at the downstream sensor under the same conditions. Does it agree with the upstream sensor?

Downstream does agree with the upstream 02.

I flutter the pedal and the 02 is responding.

I’ve also forced it lean by yanking the brake booster hose off.

Agreed is not a lean condition, suggestion was to check maf in deep.

What happend with fuel trims when disconnect MAF?

I used a volt meter to check my MAF as it was plugged in.
I have a 7 wire connector going into the MAF.
The MAF is only sending .13 volts at IDLE and when given throttle it doesn't show a smooth response. In fact, it jumps from .13 to to about 4.8 up and then gradually rises (with throttle to 7.5 ish). I think with the MAF jumping from .13 volt to 4.8 is probably a clear indicator that it is the MAF failing. Ordering a new MAF and will update when it is replaced. I tried the VE calculator and it gave me VE = 15. Not sure if I used it properly.