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1994 ranger 4.0

Discussion in 'Ford Trucks' started by Ken S., Nov 7, 2017.

  1. Ken S.

    Ken S. New Member

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    I replaced my tps. And now I'm getting code 121. Did I get a bad tps? Just trying to get all these codes figured out. I like my truck but tired of one thing after another.
  2. Action

    Action Moderator Staff Member Respected Member

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    How many miles on vehicle?
    Besides the CEL that is on what are symptoms of the engine?

    Potential causes for that code
    A code P0121 may mean that one or more of the following has happened:

    • TPS has intermittent open or short internally
    • Harness is rubbing and causing an open or short in the wiring
    • Bad connection at the TPS
    • Bad PCM (less likely)
    • Water or corrosion in connector or sensor
    >>>>>>>>Action
  3. Ken S.

    Ken S. New Member

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  4. Ken S.

    Ken S. New Member

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    IT acts like I have an old carbureted motor. In the mornings i have to let it warm up for awhile before I can evendors drive it. It will spit and sputter. Now that it's cold it's worse. But after it warms up it runs like a champ. Let it sit for an hour after driving I back to square one. It has around a 150,000 miles on it.
  5. Action

    Action Moderator Staff Member Respected Member

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    Based on what you have posted it sounds like the fuel mixture is too lean or not rich enough for cold engine operation. Crack the throttle and you are introducing more air and effectively leaning out the mixture unless the controls signal the injectors to squirt more fuel under these circumstances. As the engine warms up the fuel mixture does not need to be as rich and can be leaned out. So the cycle time for injectors can be shortened.

    Part of the cold or colder engine start up cycle would be high or higher engine RPM. The job of the electronic engine controls would be to warm up the engine as fast as possible. (A warm engine runs more efficiently and burns less fuel)

    Does the engine RPM start out high or higher under cold start engine?
    (And then come down to a hot or warm engine RPM)
    Is the P0121 the only code shown?
    At this mileage, have you replaced the oxygen sensors?

    Look at the TPS connectors. These need to be clean and tight when connected.
    Look at the wiring harness to the TP sensor for cuts, nicks or warn spots.
    It is possible the TPS sensor is bad if the above items check out OK. You might pull it off and make sure the movement of the sensor where it engages the throttle body moves smoothly.

    >>>>>>>>>>>>>>>>Action
  6. Ken S.

    Ken S. New Member

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    I also have a 327 egr pressure to low. Something like that. I just put a new egr valve on.
    I haven't got a code for my O2 sensors yet.
  7. Action

    Action Moderator Staff Member Respected Member

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    The job of an oxygen sensor is to tell the processor how rich or how lean the burned fuel mixture is coming out of the engine. The oxygen sensor like all sensors and actuators is tested by the processor initially and continuously to verify they function. If the devise returns an electrical signal that is close to what the processor is looking for no code is generated. When the signal is either NOT returned (on a test) or returned with a signal that isn't inline with the programing the CEL is tripped and a code is generated.

    However the oxygen sensors are like spark plugs. They wear and wear out. They will produce a signal however that signal will be slow. Too slow for the processor to make relevant changes in fuel mixture on time. (That is what the processor does with the O2 signal. It adjusts the fuel air mixture) Replacing O2 sensors is mostly maintenance even when they do not generate a code. Check this site out or search on line oxygen sensors problems, symptoms or anything like that.
    http://www.oilfiltersonline.com/blog/index.php/2011/01/5-signs-your-o2-is-bad/

    Question - Replacement of the EGR valve ... did that remove the P0327 code?
    NOTE the only time the EGR valve should open is on a warmed up engine and the vehicle at speeds greater than 30to 40 MPH. If EGR is open at all on a cold engine ... yes you will have rough running.

    >>>>>>>>>>Action
  8. Ken S.

    Ken S. New Member

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    I'll look at that site. Yes that code is showing after changING the egr valve. Thank you so much for helping out.
    Action likes this.

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