I'm doing some research and collecting data while I let this thread gather input...

This has just started today, my car is lightly stumbling at highway rpms. I open up torque and check the data. First thing I notice is that the long term fuel trim is at 0% even though I didn't reset the ECU. So I check the readiness codes and both the catalyst and o2 sensors are incomplete. I'm waiting for a CEL once the 2nd wave of readiness codes goes through.

So the LTFT is low. Its typically at -5.5% but after driving around in a combo of city and highway its only at -.8%. On top of that I check the STFT and its looking weird. Im seeing spikes as high as +43%. At idle I watch as the STFT slowly climbs from +10, 20, 30, 40% with each reading of the app.

I get the car home, let it run and pop the hood. Nothing appears wrong, no disconnected hoses. I see no abnormalities in the timing advance, idle rpm, coolant temp. The car idles a little rough but thats normal.

I rev the engine up to 2500 and check both o2 sensor readings. Neither of them move by more than .5 volts, the upstream is reading around .1 volts and the downstream is .8 volts. When I was driving I would see some activity from the sensors but now I see almost none. The ECU says its in closed loop though.

I've replaced both these sensors within the past two years. But what I'm stumped by is that both sensors are acting funny.

So recap:
Positive fuel trim, especially at idle
Lean exhaust (rich fuel adjustment)
Both o2 sensors acting funny
No apparent exhaust or vacuum leak
Stumbling at high rpm
loudly ticking fuel injectors (not valve ticking, this has been happening for a little over a month though)

I'm gonna do a fuel pressure check, vacuum gauge test and get some raw data posted but I wanna see if you guys have any ideas too.

Replace my o2 sensor is my initial thought but I wanna double check before doing it since its relatively new.

Thanks

 

Update:
Heres the data, the car was warm enough and went into closed loop. I let it idle a while then revved it to 2500. I then revved it higher. I saw nothing significant from the o2 sensors. The vacuum is reading low but I hooked my actual gauge up and it read 23 in/hg. I think torque is reading something wrong. On the screen it said the same too.

 

Do a real and meaningful exhaust leak test. I like to use seafoam since it will make a nice white smoke where it's leaking. A small exhaust leak is almost impossible to see with the eye without the help of seafoam or some sort of smoke.

 

Thats a good idea. I have some seafoam in my trunk.

I did a fuel pressure test and thats 32 psi at idle. A little low but I was suspecting the fuel pump...

A leak would cause o2 sensor issues. But a lean exhaust?

 

Simple suggestion and you're a genius for thinking so practically.

It was from a stripped bolt on the head I had that I thought was secured. My header had seafoam coming out of it.

Thanks, you made my diagnosis quick and painless. And my car got a seafoam treatment outa it

 

all good...always glad to help

 

Thanks