I have a 2005 ford focus 2.o liter. scan lopes at idle and stalls at red lights unless you keep foot on gas.scan tool says p0171 and p2195. changed both o2 sensors and fuel filter. scanner now reads p2195 system lean bank 1. and live data on scanner says fuel system bank one ol,fault and fuel load is 43% at idle

It is likely that the engine management system has lost its base line calibration. If the battery is weak and during the crank to start the voltage dipped low enough the Engine Control Module lost its calibration. If the pedal is depressed during the crank the TPS (Throttle position sensor) will lose the idle position for the throttle. The hunting and surging and resultant stalling is the ECM seeking out the limits and re-establishing the throttle idle plate location.

If battery is OK than running the car allowing the calibration of the vehicle to reestablish itself will correct the problem. My experience is that this happens if the gas pedal is depressed during crank with a very very low battery voltage. Always the best way is to not touch the pedal during any cranking starting procedure. Or after a battery replacement.

To accelerate the calibration process attempt to run the car ingear tring not to allow the car to stall. After afew munites the car will have reestablished its normal running calibration and you will be allset.

looks like its all emission stuff

Hi david its a focus with bad idle the pcv pipe is broken its connected in the back of the trottlebody i change dozen of those ill try to find you a video about it

You obviously know nothing about todays
technology or codes

If had of Googled the code, you would see
it has to do with an Oxygen Sensor

Google: OBD P2195 Ford Codes

Vehicles have no way to know what fuel your putting in them

fix the problems
__________
autocom cdp pro can work on Ford

Could be a problem with the MAF sensor but if it is you should have a code for that too.
Other causes include low fuel pressure, and a vac leak or air leak in the intake hose to the MAF.
The codes mean the ECM can not make the injectors rich enough to make the O2 sensors switch back and forth.

The descriptions for your codes are:
P2197 - H02S (RF) signal stuck lean
P2195 - H02S (RF) signal stuck lean
P2187 - Fuel System too lean at idle
P0102 - MAF circuit low input

Essentially what's happening is that your MPV is running too lean when at idle. Too much air and not enough fuel. As you speed up - it forces more air into the system which alleviates the problem.

Examine your mass airflow sensor. It should be completely clean - no fuzzies on it at all. If so - purchase some mass airflow sensor cleaner to clean the sensor. ONLY USE THE PROPER CLEANER TO AVOID DAMAGING THE SENSOR. Disconnect the battery to reset the system and turn off check engine light.

Otherwise you will need a scan tool to look at the voltages being supplied to/from the PCM for each of the Heated Oxygen Sensors and the Mass Airflow Sensor to determine which part is creating the problem.

Even though your O2 sensor is showing good by your scan, it could be lazy in giving readings. It has less than a 10 second window to give the reading especially if it is a heated O2 sensor. Try a Bosch unit.

which engine light? red or yellow? Go to Autozone and have them scan for fault codes for free. Then report back results

Oxygen sensors do go bad, but having the code there doesn't necessarily mean a bad sensor.

In your case P2195 means your front oxygen sensor (on the exhaust manifold) read a lean mixture for more than 25 seconds on 2 consecutive drive cycles (2 times you turned your engine on, then off).

Ford does have a service bulletin out for that code and the code usually indicates you have a vacuum leak somewhere around the engine.

If your car drives well, I wouldn't worry about it right now. It's not a condition that will leave you stranded in any way, the worst that can happen is decreased fuel mileage.

I'd run the car for a while and see if the light comes back on, and if it does, how often. It may never light up again. If it does light up, and/or if you notice any increased fuel consumption, erratic idle (engine feels like it wants to stall at idle), or any other driveability issue, i'd start by looking for a vacuum leak before anything else...

Other possible causes could be
-Bad Oxygen sensor (possible, but i wouldn't jump to this)
-Bad injector(s) (unlikely, you'd probably notice in the way the engine runs)
-Fuel pressure issues (you'd notice this too)
-Bad engine computer (very unlikely)

A vacuum leak can a lot of times be pin pointed easily:
Start the engine and let it idle. Get a propane torch (the kind used to solder plumbing pipes) and open the gas valve slightly (without lighting the torch). Pass the torch around vacuum lines and connections (they run from the intake/throttle body to the transmission, brake booster, PCV valve etc...) When the torch comes around where the leak is, the engine speed will increase noticeably.

There are pumps available to check for this but I find this method to be quite easier, cheaper and more reliable.