2011 SOHC Power Loss

[4.0blue98]

On a good day

 

[PetroleumJunkie412]

Just an update. Replaced upstream O2s, which helped fuel economy and the power loss a bit.

Plugged forscan in last night. The cats supposed to be this hot?? Had been running 20-30 mins, no power, and mostly state road driving.

 

[Dirtman]

Cats dont function below around 600f, I'm not a scientist but I think 1,400 would be on the high end of the normal range... but still in the normal range.

 

[4.0blue98]

Looks good to me too. I had an issue in another vehicle and I looked this up awhile ago. Normally most are in normal range I think up to about 1600F. May vary depending on vehicle I guess.

 

[PetroleumJunkie412]

Well. Next step is fuel pump. Have a Kemso 340 on the shelf. Going to need it for the blower, anyways, so may as well get it out of the way now.

Not going to bother with replacing downstream sensors. Future Tuner will allow me to shut them off, so I'll just deal with it for now if they're the issue.

Will take a pressure reading before changing the pump and post results.

 

[PetroleumJunkie412]

Does the tech section list the correct fuel pressures for the sohc? 64-75psi?

 

[Uncle Gump]

That is correct to the best of my knowledge.

I need to just buy a damn service manual.

 

[PetroleumJunkie412]

I need to just buy a damn service manual.

Yeah, same here. Dumped a bottle of injector cleaner in it on an almost empty tank a week or two ago. Ran freaking great till I filled back up. Now getting misfires again. FAK.

 

[Uncle Gump]

Maybe some bad fuel?

 

[PetroleumJunkie412]

Nah, it's every fill up now. Going to test pressure this evening. If it's pump, it's pump. If not, I'm going to have to find where I have a problem.

Unfortunately I can't seem to make forscan display commanded vs actual AFRs, so I'm up sh*t creek for most diagnostics.

**** I miss megasquirt.

 

[Dirtman]

Just look at the fuel trims. Short term tells you the instant feedback of the fuel mix is vs what is commanded. Bad fuel pump would show positive numbers because the computer is opening the injectors longer to compensate for low pressure. Long term will tell you the average over time so again positive numbers means air leak or low fuel pressure. Pressure should be 65psi. Regulator is part of the pump assembly. (Returnless system). The regulator can fail wide open as well and jack up to 85+ psi which will cause a rich situation.

 

[PetroleumJunkie412]

Just look at the fuel trims. Short term tells you the instant feedback of the fuel mix is vs what is commanded. Bad fuel pump would show positive numbers because the computer is opening the injectors longer to compensate for low pressure. Long term will tell you the average over time so again positive numbers means air leak or low fuel pressure. Pressure should be 65psi. Regulator is part of the pump assembly. (Returnless system). The regulator can fail wide open as well and jack up to 85+ psi which will cause a rich situation.

Copy. Guessing it's failing lean, but unsure. Will take a look at data logs.

 

[PetroleumJunkie412]

Screenshot of forscan

 

[acsnowrider]

Very nice display--Cat temps routinely operate to 1600 degrees-- This info your displaying, for a snap shot, looks fairly normal.

What are the long/short fuel trims percentages, currently?? And can you display "graph" readings on the upstream, and down stream o2's??

 

[Monkeyboy]

Once you plug the cats they are done, they don't work better cold then bad hot, they do not recover. Not a cat issue. Fuel pressure is where you should look 1st. Hard start intermittently escpecially after sitting longer is likely pressure leaking back intomtank past checkvalve, you need head pressure to start enging and the pump is busy playing catch up while you start now. Hot pumps perform worse than cold pumps, pumps,should not be noisy unless they are failing or cheap. Please check your pressure before buying more parts. If you really think the cats are at fault, when they are "plugged" loosen them from the exh manifolds and try wide open throttle then, no improvement....not cats, big improvement....yes, cats, simple test.