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Thread: 2004 1.4 8v idle problems

  1. #1

    Default 2004 1.4 8v idle problems

    Hi all. Need some advice. I bought a c2 with a snapped timing belt. Rebuilt the head with new valves, grinder them in, new head gasket, new belt, tensioners, water pump. Started the car and she runs sweet until she is warm then she idles badly, sometimes cutting out. I replaced the plugs, coil pack, temp sender, carbon electrovalve, checked inlet for air leaks and replaced all the breather pipes but still she the same. I have plugged her into Lexia and not showing any error codes but not to sure how to use the more advanced features of Lexia. Can anyone here point in the direction of what to do next?

  2. #2


    Did you ever solve this? Similar issues here only the problems are mainly when cold. Cheers.

  3. #3
    C2 Addict Advanced Poster ozVTR is on a distinguished road ozVTR's Avatar
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    Jan 2005
    Brisbane, Australia


    Generally speaking if a sensor, coil or servo goes faulty the engine ECU knows about it and turns on the check engine light and generates a code. Unfortunately there are times where stuff "sort of works" and the ECU wont detect it.
    Fuel is the only area that comes to mind that does not have any sensors in it. Checked the fuel rail pressure?
    Have a look at the engine sensors in real time on the Lexia and see if there is anything that looks out of place or changes when the car acts up. For example if the O2 sensor shows a rich or lean cycle, it might be a sticking injector.

  4. #4


    Thanks OzVTR.

    These are the sensors I can monitor. Are the any particular 'working ranges' I should be aware of so I can see if anything is wildly wrong?


  5. #5


    Sorry it won't let me edit my post.

    Something worth noting is that when I changed the head with one from a donor engine, it was actually slightly different. The stock one used an electronic throttle and the donor one used a cable. I was able to use everything from the stock engine with the donor head except the injectors. The stock injectors didn't seem to be compatible (I can't recall exactly why) so I had to use the injectors from the donor engine.

    Not sure if they're different or if it matters, but just worth mentioning.

  6. #6
    C2 Addict Advanced Poster ozVTR is on a distinguished road ozVTR's Avatar
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    Jan 2005
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    In your picture, the bottom left and the one above it show the upstream O2 sensor. At idle (and the engine is warm) they should oscillate between about 0.2 and 0.8 of a volt around once every 2 seconds. When the engine is cold it should be a flat line above 0.5V. Watch what it does when the engine goes from cold to warm. If it goes high that's rich, if it goes low that's lean. Sounds like the engine runs fine in open loop mode but has trouble when it goes into closed loop mode (warmed up).
    I am not an expert but there seems to be a few heads in common with the 1.1L engine. Are you sure the donor was a 1.4L engine? The hole in the head for the injectors might be the wrong size which is why they didn't fit? I really don't know if this is relevant. They change specifications all the time. I can only suggest you do some research on the part numbers of the two sets of injectors and see if the flow is the same.
    I know I'm fixating on the injectors but it's all I can think of that wont throw up an engine light.
    Double checked the cam timing? If it 's out by a tooth it could cause spark timing trouble.
    You could try PMing TREK, he has more knowledge on engine matters.

  7. #7


    Quick update on my issue: I fixed it by swapping out the O2 sensor in the manifold with the one from the original engine. When I changed the head with the one from the donor engine, I took the exhaust manifold too as it was easier than removing it.

    Turns out the O2 sensor in that manifold was either faulty or wrong. It was visually different to the original sensor - whether that means it was incompatible with my ECU or was just faulty I don't know. But either way, it's now running well!

    Thanks for the help.

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