stuttering Eldo

[caddypete]

My Eldo will have a stutter when first started, if you give it gas it runs like it is firing on four cylinders,and sounds like it also.Once you hit the pedal about half way down it will take off,this has been happening for the last two weeks, the codes I pull are p0171 fuel trim lean bank 1.That I do not understand because when I pulled those plugs they were black sooty where the front bank were normal.I have replaced plugs, fpr, air cleaner,O2 sensor in that bank(also sooty black) and cleaned my throttle body. My other question is I thought once your engine was in operating temp it no longer used the o2 sensors is that correct? Because the fuel trim lean bank 1 code only sets when engine is running at normal temp, I can clear the code and by the time the computer cycles back to "PCM codes?" the SES light will come back, but if I run it in 2 nd gear and keep the RPM's up the code won't set, as soon as you shift to drive or stop at a light the code comes back.I have looked for vacuum leaks on the rear bank and didn't locate any.What sensor tells the computer to richen up the fuel for bank one? Because obviously it is giving wrong info

[MAC]

First you should check for a dirty MAF sensor. The stuttering when first start could be the MAF overestimating airflow at idle, which causes the negative fuel trim values. It will then underestimate airflow at cruising speeds, which accounts for positive fuel trim values. If this doesn't work you should perform a fuel injector flow test and balance test.

[BodybyFisher]

I think its the opposite, when the car hits operating temp it goes into closed loop and the O2 sensors take over controlling air/fuel mixture. Someone correct me if I am wrong.

Check your ignition wires for their condition and also to see if any are leaking EMF or high voltage arching into your injector harnesses...check their routing. Next time you are going to run through a tank of gas really quick, put a bottle of TECHRON in, and run it out the same day, so as not to let it sit on and fuel pump and injector windings.

[MAC]

The black soot is likely due to the PCM trying to compensate for a lean mixture by adding the maximum amount of fuel allowed. The code set because the bank 1 02 sensor detected a lean mixture and sent the information back the PCM. The PCM will attempted to compensate by adding fuel. If the PCM reaches its limit and the problem still persists, the code will set. Even when the engine’s at normal operating temp the 02 sensors are functioning.

From what I have read, it is a distinct possibility that the Mass Air Flow (MAF) is dirty. When cleaning the MAF make sure it is thorough, including cleaning electronics and connections. Also, have you tried to disconnect the battery for about 30 minutes and reconnect so the PCM goes into the relearn mode. Also, make sure your fuel and air filters are good.

A vacuum leak would likely cause P0171 and P0174 to set simultaneously.