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Thread: need help with CEL P1170

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    need help with CEL P1170

    Hello fellow Miatans : )
    I'll try to make the story short, and yes, I've searched and did some homework.

    For the last 6 years, I'm driving a manual 2005 NB, the sports suspension version.

    Lately, I'm getting the P1170 (front O2 sensor, high voltage) CEL.
    It usually lights up at high speeds, about 140 km/h.

    What I've recently changed/fixed:
    -catalytic converter + 2 new O2 sensors
    (had coils-related ignition problems about a year ago, so the converter died..)
    -new Air and Fuel filters.
    -cleaned the MAF (not thoroughly)
    -checked and cleaned O2 sensor contacts
    -didn't help, and additionally, the coils started to fail - had bad Chinese coils unfortunately, that broke apart inside the engine : (
    (what's weird, is that even though the engine was misfiring - didn't get the appropriate CEL)
    -yesterday, installed a set of new good plugs and coils
    -today, the CEL is back on!

    Symptoms:
    -low MPG (about 1L/8km, instead of 1/10 - my "regular" driving MPG)
    -sometimes, misbehavior at idle: +/- 100/200 RPM
    -before changing the coils - hesitant throttle response (gone now)
    -before changing the converter and fuel filter (which was dirty as hell) - the car felt "weaker" by about 10-15%

    -hopefully not related, but what if(??):
    weird, inconsistent electrical buzzing noises, that come and go as they please, from the relays location at the drivers left knee, under the wheel.

    Planning:
    -inspect and clean (again) the front O2 wires
    -clean the MAF thoroughly with the BG cleaner
    -clean the throttle body
    -install new ignition wires (should arrive this week)
    -add BG 44K injector cleaner
    -clean all the relays, to hopefully, eliminate the buzzing

    Any other suggestions will be highly appreciated!!
    I'm about to install a FF supercharger, and must solve this problem ASAP.

    thanks,
    Daniel.

  2. #2
    Ninja Messiah kung fu jesus's Avatar
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    Daniel, are you in the US or Canada?

    On my '99 I had replaced the O2 first, like you did, and the pre cat (Cali emissions car, two cats). It came back sooner than it should have, so I replaced the coils, changed the plugs, wires, and both O2 sensors. I also later retrofit an '01+ manifold and exhaust system to eliminate the pre cat. I never had an issue again.

    I cannot confirm this, but I believe the spec values to trigger a bad coil CEL is higher than it takes to foul an O2 and cat. So, I sort of worked backwards from the code I WAS getting to solidify the operation (ignition service I mentioned). On your '05, you have coil on plugs that my '99 did not. When I replaced the coilpacks on mine, EVERYTHING smoothed out. I also cleaned the MAF sensor. Can I also assume you are clearing the codes with a scanner afterwards?

    Did you replace all the coils on your car or just a couple? I don't know where replacing the ignition wiring would help unless the wiring loom has been cut into previously. I know this is also a default answer, but have you checked/inspected the grounds on your car?

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    I'm in Israel : )
    there are two ignition coils, each distributes to two spark-plugs. Have changed both.
    Regarding the wires, I've heard/read, that the original ones tend to misbehave.
    As I'm about to boost, it's a worth upgrade anyway, and one more possible problem source elimination.
    How do I check/inspect the grounds?

    thanks.

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    OOOOOOhhhhhhhh....OK. Can you take a shot of your engine bay? I'm still not sure which engine you have. Do you have the 1.6 or the 1.8?

    If you you coil packs at the back of the engine, yes, I replaced them both. The plug wires *generally* are only good for around 30-50k km. Sorry, it's just a little confusing. North American Models are a little different than the rest of the world, a little.

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    it's the 1.8.
    the coils sit on the 2'nd and 4'th plugs, such as here:
    http://gtcarlot.com/data/Mazda/MX-5+...-49360507.html

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    Everything I said about COP is wrong, as is the plug wire recommendation. Sorry!

    I would look up the method for diagnosing the health of your coils with a multimeter. Also, I would look up all the stock ground locations for your car, find them, clean them, reinstall.

    The majority of NB2 cars I have worked on were modified for race duty and ran standalone computers and COP ignition. Sorry for the goose chase!

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    happens : ) it's a stock mk 2.5, for now : )
    as I mentioned, I've just installed 2 new coils, and the throttle hesitation (which felt just like misfires) went away.
    You think the new coils should be diagnosed?
    Regarding the ground location - you mean the places where the ECU wiring is connected to the chassis?
    thanks

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    I am referring to the chassis grounds. There are a couple in the engine bay and elsewhere.

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    found them, cleaned today.
    also cleaned the MAF, and the throttle body intake.
    disconnected the battery, reset the CEL, drove a bit - didn't come back.
    But something does feel weird and wrong. Maybe it's the residues of the throttle cleaner, but I had a bit of throttle lag on 1'st and 2'nd gears.
    They went away immediately, though.
    Will keep on investigating..

    thanks.

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    Hope you can sort it out, would love to see pics of your roadster~!

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    an update.

    -cleaned MAF and throttle intake + all O2 connectors
    -replaced ignition wires
    -added K44 cleaner
    ==> the CEL doesn't come back.
    BUT I can still feel, that something's not right.
    At normal driving, the throttle response is sometimes hesitant.
    I'm used to a very responsive throttle, but sometimes, engaging it, doesn't deliver the power. To be more precise, the power is delivered with a variable lag of 1-3 seconds..

    Any ideas?
    Thanks.

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    Does the miss happen when the car is cold, warm, irregularly?

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    Cold, warm, irregulary..

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    another update:
    just tested another hypothesis - the TPS (throttle position sensor). (after reading some forums)
    -disconnected it, and drove a couple of miles: Idle dropped to 700 rpm, and the car felt "weak". BUT! the throttle glitches disappeared!
    -reconnected, cleared the CEL, expecting the throttle hesitations to return, but they did not!
    it really looks like this sensor is to blame.
    will keep on testing..

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    Excellent! Keep us updated!

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