From zoom to gloom

Hello everyone, my name is Charles and I recently bought a 1st year 4.7L 4x4 limited edition.
After running like Swiss watch for a year the vehicle suddenly lost its ability to manage itself by misfiring and backfiring to the point of having it towed home.
I bought my first code reader. The type that reads the ECM data codes only while engine is off.
I've replaced most everything recorded as a problem .
I'm new to this type diagnosis and I am still scratching my head as to the missing link.
At idle the engine runs like a top once warmed up, sometimes it shuts off getting there, . Lift the rpm and it stumbles misfires setting the " check engine light' ablaze intermittently.
The code now sez left bank to lean with warnings about the catalytic convertors, O2 sensors and heaters which must mean O2 sensor heaters.
To date I have replaced all 8 coils , mass air flow sensor and 8 spark plugs and just finished replacing the fuel pump and inline filter.
The cats I believe to be ok , there is no odor that would reveal otherwise. I plan on replacing all four O2 sensors this week.
Lordie I need some insight to what's happening with the engine management because all those repairs left me clueless and the engine performance the same, sorry to be so blunt upon introduction.
There's nothing to do in Pahrump Nevada without a 4x4.

 

The o2 sensors are one of the most important engine sensors. You're upstream o2 sensors tell the ECU how much fuel to feed the engine. If broken etc, they will screw everything up. Thats where you start. I'm not sure why you did all the other stuff first, without your up stream o2 sensors working nothing else will ever behave right.

 

A few semi random thoughts.

With a fuel pressure gauge, you can monitor the fuel pressure in the rail to see if it magically drops when the engine goes rough. I doubt it will.

With a noid light or other similar device you can watch various fuel injector signals to see if it becomes ragged when the engine becomes ragged.

With a conventional timing light you can watch spark to see if it becomes ragged or erratic when the engine becomes ragged.

None of this will fix the engine, but will help guide you in as to where to go.

For fun, you could clean the MAF sensor attached to the filter box, and the throttle body. There is a chance the MAF sensor has become so dirty that it's not reading air flow worth a darn off idle.

 

+1 on the o2 sensors.

What code are you getting exactly??

 

Thanks to all for the input.
The reasoning behind all the replacement decisions was mostly due to pressure from "know it all friends" and "friends of know it all friends"
Replacing all the coils is by the book from the manufacturer I was told by a former lexus shop manager , and he is a know it all with credentials.
The battery went south yesterday and after replacing that and running the motor the code reader is stating " No powertrain DTCs or Freeze Frame Data is presently stored in the vehicles computer"
You people are miracle workers! , all i had to do was contact you all.
Im slowly increasing the rpm as i write and not getting a stumble until 3200 rpms where it has a back fire and loses its mojo, thats a serious improvement though

 

I
The code reader is giving a yellow warning inre,;
O2 sensors and sensor heaters, cat and evap,
You guys are correct and guess what? Girlfriend owns me now she called on O2 sensors all the while.

 

Hey. You know at 1st the codes were all about ignition circuits ( coils) and MAFsensors, noting, air intake temperature erased all the DTC's, I'll look for them , there were codes fo

 

As of this morning the motor won't start, spins and spins like it's out of gas, the fuel level sending unit may have been affected when I changed the pump.,well see

K

 

We still don't know what code you were/are getting. This thread is very confusing.

 

Kind of a guess, but does anyone else think this sounds like a timing belt that jumped a couple of teeth? Suddenly low on power, misfiring, backfiring? You only get that on multiple cylinders when the valves are opening at the wrong time. Perhaps a tensioner failed allowing the belt to slip? The smooth idle may be a red herring. It does not take much effort by the engine to be smooth at 800 rpm once the crank and rods have enough momentum built up.