K8 Running really Bad

  • Hello all I have a 94 se and its running really bad in that When you give it more power it responds less and If I press the throttle slightly more it seams to over welm the car causing it to sputter and not go any faster. I have replaced the VAF sensor as that seamed to be the cause but not helped and had a diagnosis test done by a mazda dealer garage but nothing came up (it lies) I am now stuck as what to do as Mazda advised that I will need to spend lots more to find the cause of the problem.

    If you disconnect the VAF sensor the problem is like that but the car does idle fine.

    Please help

  • I had the same shit, if you put a jumper between the ten and gnd slot in the diagnostic box the car will behave good (less power) but it will work.
    Never found out what the problem was so I fixed it by dropping in a 2.5 :twisted:

  • If that's the case it's running better in limp mode, therefore the ECU is unable to create the best map in realtime. To that it needs quite a few sensors such as:
    heated oxygen
    coolant temp
    VAF/air flow
    Air intake temperature (inside the VAF housing)

    IF it was me I would try and pull codes again using and LED as per the guide in HOW TO section. If nothing I would:
    check timing with timing light
    consider running injector cleaner
    question the state of the fuel filter
    borrow a known working VAF

  • he had a known working VAF
    mine 8)
    that was working perfect when the 1.8 came out
    so you can rule that one out

  • Gonna try Epic's idea at the weekend. May seam a silly question but wheres the diagnostic box and are the jmpers all labled so it will be ok to put a jumper between the ten and gnd slot. Also is it a lot of power loss?

  • TEN and GND puts it into diagnostics/limp mode. IIRC It will run off a default open loop map, meaning it will not optimise performance by monitoring temp/knock/o2 mix. It will be a noticeable powerloss, I'm afraid, these sensors are there for a reason!

    In short, fix it :P

    The diagnostics box is near the firewall, accessible by leaning over the passenger side wing. The lid should have all the pin labels, so you should be all good :)

  • Will do the jumper for a quick fix. But if doing that does make the car run ok but with less power then the problem will be one the sensors. What sensors are turned off when doing the TEN and GND jumper?

    I have replaced the VAF sensor but stills does the same
    Theromstat broke as well so thats been replaced.

    Are the sensors easy to replace myself and are they expensive?

    Your help is much appreacted Marco and thx for explaining things you know your stuff. :-)

  • Just tried the Gnd and Ten jumper and still does the same. After putting the jumper across and turn the ing on you hear whats like sensors turning off then all starts fine but still does the same behavours as b4, its sputtering a lot and not liking more revs and when you pull away it hasatates (not good). So im guessing its not the sensors. Any other ideas please. :cry:

    If I drive it like a grannie its fine and does not sputter but cant give it any power :cry:

  • I had a simular problem
    Try unpluging the TPS my problem went away so i changed it.

  • Thx for the help but whats a TPS and where is it?

  • have a look at Alan's post ;) Hopefully it'll be a quick fix for you too, surprised you're getting no codes though!

    Could be a fuel/air starvation. Clogged air / fuel filter. Drive it here, I'll help ;)

  • cool thx will try that at the weekend.

  • Pulled the error codes myself and the lying garage said there were none. I found 4 they were 12 - 15 - 13 - and 24.

    TP sensor
    HO2S - LH
    HO2S - RH
    HO2S - RH

    Where can I find these to replace them or any help or advise please.

  • Heh fools! Sort of reasons why I don't trust anyone to work on my car!

    oxygen sensors:

    Though I'm sure there's other places sell them too. They're a bit awkward to get at, well mainly the rear one. Some places sell these with connector some just with wires. I'm sure Mark at fordprobestore.co.uk could sort you out.

    For the TPS, best bet is to get a scrapyard one, they're a complete rip off from Mazda/New. There's a chance it might just need cleaned too.

  • Is this the one?


    There is a 3 wire and a 4 wire one. But its does not say heated oxygen sensor just Lambda/O2 sensor 3 wire Higher Quality

    Also on the test it gave 3 errors for the heated oxygen sensors are there 3 or just 2, the LH and RH and are they the same part for both?

  • Are the HO2 sensors in the same place on the mx6 as the mx3 as I have a haynes manual for the mx6?

  • I have changed the 2 heated oxyen sensor and cleared the fault codes took the car for a drive and it was a little better but still not right so I checked the errors again and nothing. Car still running bad so I gave it a few days and tested again getting a fault code on one of the sensors (RH). Could this be a faulty ECU or something else please help.


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