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Terri 12/7/2016

2004 Mercury Sable LS 6 Cyl 3.00L


Car jumps and hesitates

A few months ago my car mercury sable started running rough and jumping when I pushed on gas, now it does it when I have brake on also. It was misfiring according to computer so I had a coil and spark plugs changed, it was a little better now way worse with jumping and hesitation. Doesnt want to go and then when I push hard on gas sometimes it kicks in and takes off but still runs rough, according to computer scanner now, it has code po193 which is Fuel rail pressure sensor circuit, high input. Somebody told me it may need fuel pressure regulator. I cant find one at auto parts store, was going to call dealer tomorrow. My daughter is doing all of the work, just wanted your opinion. Car has 84,000 miles. Thanks

1 Answer


Jimm 12/7/2016

First step - have the stored fault codes or check engine light scanned - for free - at any local auto parts store; Advance Auto, Auto Zone, NAPA. Then, post a reply as 'add answer' with the specific code for more assistance.

This aspect is important; there may be a fault code stored in the OBD memory which may not be displayed as a check engine light.

Do not skip this important first step - there are literally hundreds of possible fault codes. Avoid wasting/ throwing money at the problem.

Possible Causes of Engine Hesitation or Stumble:

Dirty fuel injectors (cleaning the injectors often fixes this)
Dirty air filter (change filter)
Dirty / clogged fuel filter (change filter)
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires


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