2003 Ford Taurus Lean Idle Surge

1131 indicates that your control cannot compensate for a lean condition, it's at the max correction and there's still an issue,,, could be caused by a multitude of things, some easy, like vacuum line problems,etc.. i would check all over the engine compartment, make sure all is in place, are you sure the other iss 1123??

I took it to a good independent shop and they did a diagnostic check and found B1342 ECU Fault / P1131 Bank 1 Lean / P1233 Fuel Pump Driver not communicating with PCM.

The tech is Ford factory trained and he said some of the Taurii have 'issues' with the comptuers and the PCM warranty is good for 8 yrs or 80K miles. Said the PCM should be replaced first because the ECU fault could be caused by the PCM. Says if the ECU is bad then it has to be programmed by a Ford dealers computer, so no one can replace it but a Ford dealers shop. I called the local Ford dealer and said if that is the problem they would replace the PCM free.
If I have know all that I would have taken it to Ford to start with.

He cleared the codes and it ran fine for about 25 miles then it started doing the same thing it was doing before, loping and surging at idle and does it worst when the AC cycles on and off. Other than the idle thing, I don't notice anything else wrong with engine performance and I drove it on the hwy and stomped it in passing gear and it ran like a race car.

Since the diagnostics I drove it 35 miles and the CEL has not come back on, but it started loping and surging at idle again and you can watch the tach up and down about 100 to 200 RPM's. The Ford place says the CEL light must be on for them to pull the codes but it's not on now.

Another question: Could running it lean possibly burn the valves or cause other problems in general? Reason I ask is I flew airplanes and you never run the engine to lean or you will burn valves. Some of the fuel that enters the combustion chamber is not burned, 'sacrificial' fuel that evaporates and used to cool the chamber and I wondered if that held true with auto engines.

History: Former owner was a senior citizen, (like me), and babied it big time and had all the services done and fuel filter changed at 30K mi. Now has 40,485 mi on it and when I bought it had 38K mi on it. Used mostly for around town jaunts, running errands and shopping and we have a big car for trips. 03 SES Vulcan engine. The temp gauge has never went above normal.

I think the Feds require the 8 yr warranty on certain emission control parts, there may be more pieces covered also.. as far as lean run, I don't know, supposedly pistons can hot-spot, valves can get damaged, etc in severe lean conditions.. I would get it fixed up, it won't pass emission if your state has it anyway, I wouldn't chance it.. try cleaning out your iac unit, idle air control, sometimes they can cause idle problems . For the fuel pump driver issue, could be a wiring issue, resistance, or even if your fuel shutoff has been tripped and reset, it might show up in that event... needs to be diagnosed, worst case is pcm at fault and needs to be replaced and reflash

I live in SC near Savannah, GA and we don't have emission checks here. Yes, the Feds dictate the emission components law warranty good for 8 yrs or 80K miles. I agree with your analogy if the CEL light is on that usually means something needs to be fixed verified by the tech that pulled the codes.

You have been a big help and I certainly appreciate your time and soon as the CEL comes back on I'll run it into the Ford place and let them fix it. Over the years I bought about ten vehicles from them so I'm in their good graces asnd after they get it fixed I'll check back and let you know exactly what they did. Thanx again and have a super week end.