02 hesitates, service engine light blinks, A/C warms

Discussion in 'SN95 V6 Mustang Tech' started by plonqz, Aug 6, 2010.

  1. hi all, first time poster to the stang forum...

    02 v6 mustang revs very high when starting. "service engine soon" light is on all the time. approaching 40 mph, especially when going uphill, car hesitates and bucks, "service engine soon" light blinks, sometimes for a long time, before going solid again. at the same time the service engine light starts blinking, the A/C goes warm and does not begin to cool again until service engine light goes solid.

    i am pretty handy with fixing things around the house, i can take apart and repair washing machines, laptop computers, etc, but with cars i just take them to the mechanic.

    but after spending $1800 at sears 6 months ago for this mustang and having it run like crap, i figure maybe i can do a better job for cheaper. at the very least, maybe if you folks give me some insight about it, i can avoid getting ripped off.

    any suggestions? i heard i might be able to take it to pep boys or auto zone and have them read the computer codes for free, is that true?

    thanks in advance for any help.
  2. Welcome.

    The blinking check engine light means the car is misfiring. Go to the autoparts store and have the codes read. Please post the FULL codes.

    When was the last time the plugs were changed? Spark plug wires?

    Clean the mass air flow sensor (MAF). Use only cleaner designed for the job. The sensor is easily damaged.

    Check for vacuum leaks. This is IMPORTANT as even a tiny leak will cause problems.

    Please review Post #8 for the idle problem.


    IMO, the AC is turning off because the car is in "limp in mode". Fix the blinking check engine light and the AC problem will go away.
  3. And for future note, don't take it to Sears next time. I would not trust them with anything except battery and tire. Probably would have been better to just have taken it to a Ford Dealership. Just my thought. I still take my Mustang to the dealership for brakes, etc and whatever I can't do on my own.
  4. TSB 02-22-1 misaligned CMP sensor

    Please note that there is a Ford TSB that calls out an issue with a bad misalighed CMP sensor. The text of the TSB is included below. IMO, it is too soon to look at this as the problem. The other usual causes need to be ruled out first.

    Please update the post with the results so that others may learn as well.

    Article No.



    1994-1997 THUNDERBIRD
    1995-2003 TAURUS
    1996-2003 MUSTANG
    1995-1997 AEROSTAR
    1995-2003 RANGER, WINDSTAR
    1996-2000 EXPLORER
    1997-2003 E SERIES, F-150

    1994-1997 COUGAR
    1995-2003 SABLE
    1997-2000 MOUNTAINEER


    Incorrectly installed gear driven camshaft position (CMP) sensor synchronizer assemblies may be hard to diagnose. Vehicle may exhibit poor fuel economy, driveability Diagnostic Trouble Codes (DTCs) P1336, P1309, P0340 with MIL light on. Loss of power, surge, hesitation and runs rough on acceleration may also be present.


    New diagnostics have been developed for WDS to diagnose incorrectly installed gear driven camshaft position (CMP) synchronizer assemblies. Refer to the following Service Procedure to diagnose a possible mis-installed synchronizer assembly and proper installation procedure.


    Items Covered In This Article

    ^ "Hall" vs. "VRS" sensor function
    ^ Vehicle history scrutiny for past service of the synchronizer assembly
    ^ WDS - Power balance test
    ^ WDS - CMP and CKP wave signal comparison
    ^ Wave Comparison chart - CMP vs. CKP
    ^ Correct (CMP) synchronizer installation tool application & installation procedure
    ^ "Top Dead Center" (TDC) alignment
    ^ Synchronizer installation tool application chart

    Hall - Effect (Hall) and Variable Reluctance (VRS) CMP Sensors

    CMP sensors are used on all current model year engines, regardless of fuel system or ignition system type. The CMP sensor provides the Powertrain Control Module (PCM) with cam position information to indicate # 1 cylinder, on the compression stroke

    There are two different types of CMP sensors:

    ^ The three-pin, Hall-effect sensor (Figure 1)
    ^ The two-pin Variable Reluctance sensor (Figure 1)

    Although the Hall-effect (three-pin) and the Variable Reluctance (two-pin) CMP sensors perform the same function, their signal appearance is quite different and they are not interchangeable.

    ^ The three-pin Hall-effect sensor uses a Hall effect device and a magnet to generate a digital square wave signal (Figure 2)
    ^ The two-pin Variable Reluctance sensor is a magnetic transducer, which uses differential voltage across windings to generate a voltage waveform that is similar to a sine wave (Figure 2)

    Both sensors provide a switching voltage as the engine rotates.
  5. thanks you wmburns and chingonstang for your replies. i went to advance auto parts today. the guy who read he computer codes could identify that the car was misfiring just by listening to it first. then he read the codes and there were only 2 from what he said... the first was engine misfire, and the second engine misfire at cylinder 1.

    i believe when i took it to sears i did a tune-up along with brakes and fixing power steering fluid leak. i need to dig out my receipt and take it back to them since if it is a spark plug or plug wire, then that should not be happening so soon after a tune-up. if it's something else, i guess i can have them diagnose the problem and then i'll figure it out.

    as for the MAF sensor, from what i saw online, that does not look too hard to clean. i don't remember that part ever being replaced.
  6. Resolution

    Took it back to sears since they had done a lot of work on it before. They said it was the ignition coil pack that needed to be changed. I was ready to try to do the work myself, but since i had spent a bunch of money there before, they offered to change the part for $135 including labor, which sounded pretty reasonable. Anyway, it's running much better. All the symptoms in the title of this thread have gone away.

    Thank you all for your help :)