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Pete
Pete, Auto Service Technician
Category: Ford
Satisfied Customers: 26625
Experience:  Over 17 years diagnosing and repairing automobiles various makes and models with some training and certifications.
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My 2004 ford taurus SES has been in the shop alot lately....

Customer Question

My 2004 ford taurus SES has been in the shop alot lately.... The check engine light keeps coming back on. Everytime it gives a running lean code on bank 1. My mechanic has replaced the spark plugs and wires, checked the battery and alternator both are good. Replaced both oxygen sensors, changed the fuel filter. Replaced the Starter, replaced the ignition coil, and the Mass Flow Air Sensor. .... this is the note the left on my last invoice
SPECIAL NOTICE: O2 SENSOR CODES AND LEAN CODES ARE NOT COMING BACK AT THIS TIME. HOWEVER THE ROUGH RUNNING CONDITION UPON COLD START IS STILL PRESENT, BUT DOESNT HAPPEN LONG ENOUGH TO CHECK THROUGHLY. WE SUSPECT THE IDLE AIR CONTROL VALVE, HOWEVER, WE WOULD NEED MORE TIME TO CHECK PROBLEM.
and this one was from the previous time i took it in
SPECIAL NOTICE: CODES: PO300 & PO316, MISFIRE DETECTED AT START UP. TEST DROVE VEHICLE NO MISFIRES DETECTED DURING TEST DRIVE OR START UP. MAY NEED TO LEAVE VEHICLE OVER NIGHT TO CHECK DURING COLD START UP.
so i left it for 5 days with them. Its still running the same, during idle its still dropping low in RPMs, 400 or so and it bounces from 400-700RPM. Also it has randomly started to try to surge forward? I stopped to get my mail this morning and it shot forward a good 3ft before i hit the brake. Theres so many weird things going on at the same time... I really need professional advice, im starting to think my mechanic does too at this point :/ ...
Submitted: 1 year ago.
Category: Ford
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

With all that has been replaced here and with the code only for a lean issue on bank 1 one common fault I have seen to cause a lean issue only on one bank when the oxygen sensors have already been replaced is one or more of the fuel injectors atomizing incorrectly on bank 1.This wont cause a misfire but will cause a lean code to set.If the fuel injectors have not been tested or cleaned at all this should be done to see if this points to the fault here or corrects the fault.In some cases you can add a bottle of injector cleaner (I recommend chevron) to the fuel tank at 1/4 tank and run the tank to near empty and repeat to clean up the injectors and this may resolve this here.In other cases the injectors need cleaned with an injector cleaning machine to correct this and worse case scenario if one or more will not clean up the affected injectors will need replaced.

The other issue I have seen is intake gaskets leaking.This wouldnt be a leak where you would see oil or coolant leaking but instead a leak where the engine is sucking in excess air past the gaskets causing the lean condition.To check this a smoke machine is needed to inject smoke into the intake to see if the gaskets are leaking.If the gaskets are found to be leaking then they will need replaced.

Both of these will cause this issue here needing checked into to locate which is the cause then repaired from there.This will cause rough running and may or may not set fault codes.The surge and idle jumping can be either the vacuum leak or the injectors needing cleaned or one or more needing replaced.I would have these checked into further.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete