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Thread: Worlds most annoying Z18XE ....(Lots of info)

  
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    Worlds most annoying Z18XE ....(Lots of info)

    Hi

    My Z18XE is a real pain in the behind ..

    Symptoms are lumpy idle and often it is undriveable the first minute or 2 from cold. After that the car resumes normal operation and only the lumpy idle remains...Oh yeah and the emissions warning light.

    So basically it idles like a sack of potatoes, opcom says desired speed is 875RPM but it jumps between 700-900..

    I have 2 videos of the engine in idle.

    First off is the engine itself.

    http://217.157.194.50/engine.3gp

    Then there is the exhaust.

    http://217.157.194.50/exhaust.3gp

    Both videos play fine on my windows media player and vlc player.

    If i reset the error codes the emissions light will go out but after only a bit of driving the error code will return and a day or 2 after the light will come on again.

    The error code i get is :

    P0170 - Lean Exhaust
    (02) - Present

    Someone told me that this code was often related to the MAF so i went out and bought a new one but there is no difference with the one or the other. Oh and i have tried both for a period of time to make sure that it was not just the ECU needing to adapt.

    I also just made a recoding of livedata, dont know if this will help.

    http://217.157.194.50/livedata.csv

    It is a recording of idle, accelerating to 80kmh, driving for a bit and then down to idle again..

    I noticed that the spark angle was flying around when idling...Dont know if this gives any clues....When driving it seemed to be steady.

    Also i have cleaned the TB and today verified that everything is still ok with the tb.......Found the pinhold had clogged up again and that the pipe that the pinhole is attached to the hose with had split so i put a clamp on that hose and tightened it. (Doubt it had anything to do with it since the hole was blocked but clearing it did not help anything.....BTW there was no clamp on that hose before ???)..

    Have been looking around for leaks in the exhaust system but found none.

    Car seems to be doing a little less mpg than before i got this problem.

    Also the idling has become so bad that when i stop at a traffic light i can litteraly feel the car jerk because of the engine cycling up and down i the revs...

    Hope someone has seen this problem before.

    Zafiraowner

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    stevej66's Avatar
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    O2 sensor is open loop and should be closed loop, this will be causing the lean code. i would replace both sensors with new quality bosch units

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    Quote Originally Posted by steve1412 View Post
    O2 sensor is open loop and should be closed loop, this will be causing the lean code. i would replace both sensors with new quality bosch units
    Ok will do.

    And this faulty O2 sensor will be able to generate the rough idle and so on ?

    Where to buy good quality O2 bosch sensors cheapest ? Vauxhall's pricelist always comes with a guide on what organs to sell to be able to afford the part...

    Also, if i wanted to try and save money by only changing the bad one, which one would i start off with ?

    After looking the data over again i see that there is actually alot of "closed loop"....So just need to have something clarified here......If the car is at running temperature and idling the loop should be closed right ? (Seems it is indeed open when idling as you say)...

    Also...Why is Calculated throttle position "Idle", "Partial Load" and "Invalid" ??? Invalid does not sound right does it ?

    Zafiraowner

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    possible air leak, my first thing would of been air flow meter of which you have done!

    any sucking noises?


    other things like fuel pressure, exhaust blows can cause faults

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    If fuel pressure could be causing it, as suggeted by warren, check the fuel filter? Some people don't change them and they can rust through. The one on my old Ka looked like it had been at the bottom of the ocean...
    Just an idea.

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    Regarding air leaks.

    I have cheched all intake pipes and found no splits. Only problem i found on re-examining my tb was that the pinhole had clogged up again and the pipe where the hose attaches was cracked but i have cleared the pinhole and put a clamp on the tube so that there is no risk of leaks there.

    I do have a whisteling noise when accelerating over 4500 RPM's but this is only when accelerating. If i rev the engine in neutral i dont get that sound.

    Had the lambda sensor out yesterday to be able to take off the heatshield and found no holes in the manifold or any place where it wass blowing. Also the previous owner had the cat/exhaust manifold assy replaced a few years ago just before i bought the car.

    Earlier i have changed the exhaust and i also tested the flexi hose on the exhaust pipe by taping a plastic bac over it, starting the engine from cold, blocking the exhaust pipe in the end and the bag did not inflate so i guess that it is not leaky but can recheck if needed.

    EDIT : Just tested the exhaust system....Had the wife block the end and had a feel around for air leaks but when the system was very pressurised to the point where the engine almost stalled the exhaust gasses escaped where the 2 parts of the exhaust was joined....This is well after the lambda's and it was only when really pressurised it was leaking there.

    Also i found a site where they explained how to test the lambda with an oscilloscope and i did this....Sadly my oscilloscope is not a storage oscilloscope but nevertheless the picture given was not anything like what they said to expect..

    Also when idling the car does actually go into closed loop at first but after that it re-enters open loop and where B1S2 O2 sensor is reading ~350mV in idle the B1S1 O2 sensor is only giving off 20 mV's and this value rises to 40 mV's when revving to 3000 RPM's ....

    Anyone know if i am right in thinking that B1S1 sensor is giving off a very low reading....B1S1 is the one in the manifold as far as i can see..

    Honestly i think i am just going to change the O2 sensors just to get rid of this failure possibility..

    Zafiraowner

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    m4rcus66's Avatar
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    i have same problem with my astra coupe so let me know what it is annoying i know

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    as i said before, your symptoms are typical of lambda sensor problems and i would replace both for bosch units. i use http://www.lambdapower.co.uk

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    Quote Originally Posted by steve1412 View Post
    as i said before, your symptoms are typical of lambda sensor problems and i would replace both for bosch units. i use http://www.lambdapower.co.uk
    Will do as said.

    Looking at this link

    http://www.lambdapower.co.uk/partsea...ine_code=Z18XE

    There are 2 front ones (diff. wire length, will buy whatever one fits mine regarding length) and one rear one.

    Are these Bosch ones ? I cant seem to figure that out just by looking at the website..

    Zafiraowner

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    My car's also like this, it has been for yonks, was about to start spending a bit on mine cuz its doing my head in, but i think i'll wait and see how you get on with yours - you seem to know what your on about.

    Had my car now for 7 yrs (Astra Coupe 1.8 - 2000 'W' plate), to be fair had no real probs apart from the lumpy idling & jerkyness & the actual revs bouncing about all over the place, for about a year i put it down to the shoes i was wearing - lol, but now its doing my head in, its not got worse or owt, i've just got by really mainly cuz i work about 5mins from my house so its not all that bad, all I have ever done is clean the throttle body out a few times, but all that ever does is brings the revs back down when idling & then after 3-4 weeks or so its back to where it was.

    I've noticed now every time when I start up in the morning, the revs will go upto 1100-1300 and stay there unless i give it some gas for a second n let it come down a bit...
    Keep it real!

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