I ran the live data test again today on the way to work. Looks like LTFT pretty solid 8.8% unless I really punch the gas then it'll go down then come right back up. STFT stays around 0 +/- 3.. Also it's reading "open loop - drive" I'm not sure what that means? Is that just enriching the mix for power? Or is that cause a bad o2?

 

Open Loops means it's not entering Closed Loop so ignoring the O2s. Was this done with the engine cold? Gotta warm it up a bit first.

 

It was done at operating temp. It does enter CL when idling and driving but It enters "OL-drive" under more power, for example going up hills or going over 40 mpg.

 

40MPG?! :O

Under heavy throttle yes it kicks out into open loop. That's normal. Not when going over 40 MPH though... it's just based on amount of throttle application.

How was the throttle position sensor tested?

 

Haha sorry I meant MPH. Because I don't have much power I'm usually giving it a good amount of pedal over 40. I didn't mean the actual speed was the reason why it went into OL. sorry, I'm responding in the short spurts of time I have at work. TPS was tested by I coming volts and outgoing volts also I can monitor it on the scanner. The TPS should be fine. I'm thinking more and more that it's the o2 sensor

 

Update. I've replaced the O2 sensor been driving it a few days. Seems to have not helped much if any still running rich about 7-9.% LTFT. I've got a small exhaust leak post O2 pre cat. Will be replacing down pipe soon. Other than that. Back to the drawing board. Going to look into testing the ECT again. Looks like it's running a little cooler than normal the past couple days. 204 rather than the typical 210 that it's always been. Possibly a thermostat issue.. Any input guys? Thanks

 

im no pro mechanic but after reading what you've done so far its hard to believe something so small is going to be the culprit for a 6mpg loss.

are your brakes possibly seized?
have you checked over your driveline?

 

I might have some insight on the trims. I tune chevy's on the side so I don't know much about the Jeep specifics but I do understand how the sensors all work together. Your open loop/closed loop sounds normal. The engine is trying to maintain a stoichiometric air/fuel ratio. That means not rich not lean. Chemically, that means that all of the oxygen gets burned and no excess fuel is left afterward. The O2 sensors are only accurate at that air fuel ratio and they will read about 450mV at that ratio. When the AFR gets rich, the O2 sensor will jump up to around 800-950mV and the computer will start decreasing the STFT (short term fuel trim) until the AFR gets lean. At that point the O2 sensor will read near 0mV and the STFT will start to increase until the AFR is rich again and on and on. The O2 sensor is really just a switch. It reads rich or lean and commands the computer to fix it by increasing or decreasing the injector pulse width accordingly using the fuel trims. In closed loop, the O2 voltage should be oscillating. The STFT is not stored, it only commands instant adjustment by the computer. If the average STFT is high or low over some time, the computer will store a value in the LTFT and basically start there so the the STFT does not have to correct as much. Therefore, if everything is working as it should, the LTFT should level out and the STFT should stay near zero. This means when diagnosing your Jeep, you should be more concerned with the LTFT.

When you're under heavy throttle it will go into "power enrichment". When it does that, it commands a richer fuel mixture for power and the O2 sensors are not used since all they know is that its rich and not how rich. Then the computer is just commanding the AFR based on what it thinks is the flow rate of the injectors and flow characteristics of the motor under that particular load. It all programmed in there and when we make changes to the engine, the computer doesn't have any way to know that.

Anyway, if your O2s are oscillating under light throttle, then your system is working as it should.
If they stay around 450mV, then they are probably not working.
If they're pegged low then you're either running lean from an injector not working or you have an air leak. This will often cause it to run rich since the O2 sensor sees extra oxygen, thinks its running lean and keeps raising the fuel trims (adding fuel) to try to correct it. Your exhaust leak could certainly cause this to happen.
If they're pegged high, 950mV or so, and your LTFT are in the negatives, then your injectors are too big and it can't adjust accordingly.

I love talking about this stuff so if I've said anything confusing, tell me and I'll try to explain better.

 

Exhaust, I've checked both of those everything's good there thanks!

Axekick, thank you for the in depth reply I appreciate it! I'll be changing the down pipe sometime after Christmas. I'm also thinking about changing my injectors (again) because now that I know more about injectors they're not flow matched at all! They're flow is about 30cc behind stock. I'm thinking that may be a large proponent of why it's running bad. But Like I said before I don't know much about fuel system so I may be wrong. I was thinking maybe because they don't flow as much the PCM can't figure out the right mixture? Idk. I'm thinking about going with 784s

Thank you all for quick replies I'm at a point where I'll take all the advise I can get haha

 

"Exjay" not exhaust. Damn iphone.