Ok guys I have a 04 5.4 Lariat that has about 230,000 miles on her. I just did my 3rd or 4th plug and cop change. It's been starting to run really horrible after the last change which was past Saturday. I can barely even move at all. Don't even think of pulling out in front of something unless there a mile away. I have the torque app on my tablet and a ultragauge I think that's the name and there both reading the same p0174 lean bank 2.

My vacuum and fuel pressure are good. What else would cause this. I'm pretty sure my cats are shot would that cause the code? Bad O2 sensors? I think there original. And help would be greatly appreciated.

 

Vacuum leak.

 

A bad O2 sensor cannot cause your symptom. As glc stated, it's probably a vacuum leak. Most likely you broke something without realizing it.

 

Either that or you knocked connectors loose or broke wires on one or more injectors on the driver's side.

 

I will check that out first thing Saturday morning. Last night I did a quick look over and didn't really notice anything but it did sound like a vacuum leak somewhere. I was spraying carb cleaner and nothing changed. I'll have to look better tomorrow morning. Last time I had a vacuum leak my 4x4 was trying to engage and I found it was a check valve. If I had a leak now would my 4x4 try and engage?

 

That won't work anymore, the computer is too fast.

You can spray and watch the computer's response via the short term fuel trims, that works.

 

Ok thanks. I'll try looking things over tomorrow.

 

You shouldn't spray with carb cleaner, it's hard on rubber parts. Use an unlit propane torch.

 

I gave up. I've been working on it since 6am. I can't find a vacuum leak. Everything seems ok. I'm going to take it to a mechanic that I trust. Thanks for the input guys. I'll let you know the results when I get it back.