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Thread: Problem with a Ford Focus Misfiring

  1. #1
    Join Date
    Dec 2008
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    2

    Default Problem with a Ford Focus Misfiring

    Hi

    I recently (abt 1 month ago) bought an 02 reg ford focus 1.6 zetec with 90k on the clock. It has been serviced regularly (every 12K), and has all the stamps and reciepts to prove it. Last week (Mon) i was driving along when i lost all power and the car began to judder. I towed it to my local garage who replaced the Coil Pack and everyting seemed to be fine, however three days later i began experiencing a lack of power through all the gears in low revs (below 3000), but not a total loss as on the monday. I called the AA out who plugged their machine into the car a said that the cylinders were mis-firing, so i took it to my garage again who replaced both the Ignition Leads and the Spark Plugs, however to no avail.

    I then took it to a different garage with a diagnostics machine and explained what parts had already been changed. After the diagnostics they have said its a problem with the ECU and that i'd have to contact a different company for a test and possible replacement of the ECU. To date i have spent 30 on a new coil pack, 25 on new leads, 10 on new plugs, 60 on diagnostics and now i'll have to pay 40 for the ECU test and a possible 200 for its repair or a new one.

    Before i do this i wanted some advice on whether it may be a problem elsewhere, i have read that the MAF can cause a similar mis-fire however i cannot find it in my engine, also ive heard it may be an electical connection fault somewhere.

    Finally if i do have to remove the ECU to take it for a test can anyone explain to me where it is located and how i can find it??

    Thanks in advance!

  2. #2
    Join Date
    May 2007
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    5,240

    Default

    They are probably right about the ECU. When the coil packs fail they can damage the output circuit within the ECU itself.

    The ECU is behind the drivers side footwell panel.

  3. #3
    Join Date
    Dec 2008
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    2

    Cool

    before taking any further action what are the fault codes if any ???.
    i have seen a few with random misfire detected and everybody replaces the coil,leads and plugs to find it does it a few days later.
    check to see if there is a sensor in between plugs 2 and 3 . if so check that the wiring for it has not been caught when a cambelt has been replaced.
    if wiring good you want to replace sensor first to see if this cures fault.
    this is a cylinder head temp sensor.

  4. #4
    Join Date
    May 2008
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    8,531

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    Exactly!!! At last someone who understands that a 'random misfire' is NOT a plug, lead or coil problem. If the fault code is P0300 it is NOT one of the above, but an indication of another type of fault, mostly commonly a mixture problem.
    While the cam belt may not have been changed yet, as it is not due until 100,000 miles, the advice about the cylinder head temp sensor is valid as earlier models had an interference problem.
    The wiring to the temp sensor runs alongside the HT leads of nos 1 and 2 plugs. This wiring could pick up interference from the leads. It was recommended to ensure the wiring was as far from the leads as possible.

    The fault may still ultimately be the ECU but if it was my car, I'd go to a breakers and try an airflow sensor first. (If the garage that did the diagnostics checked the long term and short term fuel trims then this should have eliminated the airflow sensor. Even if they didn't understand this check, a live value of the upstream oxygen sensor may have shown a possible fault.)

  5. #5
    Join Date
    Dec 2008
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    Default

    thanks for the advice.. i took the ecu out and took it to an auto electician. he said it had failed the test on a small output diode so he replaced it, but after i explained my problem to him he recommended that i double check the coil pack, and if that was ok he would come out to check all the relevant sensors and wiring.

    i went to ford and bought a ginuine coil pack, and after fitting both the repaired ecu and the coil pack everything seams to be fine.

    i think it was my fault from the first instance in trying to use a aftermarket part. the replica coil pack was 25 and the ginuine was 110, so i thought i'd try getting away with the replica, however in the long run it would seem it has cost me more (close the 350). the lesson for me here is buy ginuine!

    i'll let you know how i get on in a couple of days, just incase it fails again.

    thanks you again, i appreciate your help.

  6. #6
    Join Date
    Nov 2010
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    2

    Default

    Hi, It sounds like you have done all the right things so far except for checking the fuel injection system!! The focus's arent common for fuel problems but worth taking the fuel rail out and cranking the engine and seeing that all the injectors are firing sufficiently. I have had this problem with a few Fords and especially my own Ford Focus, I changed the plugs, coil pack etc etc, It was still the same, so i greased the plug leads where they connect to the plug and it seems to be running excellent!!!

    Whilst I'm on, does anyone have a theory to why the Focus and some other fords just cut out when you are driving them?? My focus will just be driving along and it will sometimes cut out without a misfire or the speedo gauge will drop, i have been working on cars for years now and still dont know what the problem is, altho i'm sure someone out there will know. any ideas?? Thank you.

  7. #7
    Join Date
    May 2008
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    The usual common fault with the speedo drop is the vehicle speed sensor in the gearbox. This causes cutting out. Somewhere on this site I think it has been well covered, especially how to get the retaining pin out. Bit fiddly but for anyone used to working on cars, not a problem. May show fault code P0500 if you are lucky. If it is intermittent, ensure clean contact in the connectors just in case.....

  8. #8
    Join Date
    Nov 2010
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    Default

    aw good tip m8, never even thought of that. I'll try that first thing tomorrow morning!! Cheers.

  9. #9
    Join Date
    Apr 2012
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    1

    Default

    hi i have a focus ghia saloon 1.8 zetec engine seems to miss on plug 3 spark ok so have put coil pack,leads,fuel injectors still a miss will still power right up but when coasting you can feel it any ideas anyone thx

  10. #10
    Join Date
    May 2008
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    8,531

    Default

    Do a compression test in case a valve is damaged or burnt or seating badly. Also check the inlet manifold gasket for air leaks using carb cleaner or similar.

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