Slight hic-up between 1750-2100 rpm??

  • Hi fellas

    I have noticed more recently that from approx 1750 rpm to approx 2100 rpm, while driving on light throttle openings, the K8 has developed a very slight, stutter, dither, ?

    after 2100 rpm its smooth and glitch free? and when I'm more enthusiastic with throttle input it's not noticeable?

    There doesn't seem to be a link to temperature? as its there hot or cold?

    There's 'NO' codes showing and I've reset ECU, TPS and idle speed several times to confirm my settings but the 'wobble' is still there?

    Car is otherwise faultless and a pleasure to drive (thats torn it!!)

    I De-cated a month after MOT (April last year) and will soon be refitting CAT for test in March :(.

    I have noticed:

    Sooty tail pipes (Black not gray)

    Increased fuel consumption (lately)

    A smell of unburnt fuel when at normal operating temp.

    My first thoughts…..........

    O2 sensor/s ??????????
    Just hoping one of you has experienced similar and had success with a fix of some sort before I delve deeper with numerous component removal and testing????

    Any one know at what rpm/condition EGR operates at? is it just idle/decelerate?

    Guessing my up and coming MOT may be revealing?

    appreciate any guidance, comments etc

    kev b.

  • MOT passed today!…. whey hey! :P

    My initial fears were unfounded :D

    Only emission that was a concern and up from last year was
    fast idle CO @ 0.120 (0.042 last year) all others down on last year!

    I only do about 1500 mls a year so probably lack of use and getting coked up with all short winter journeys? :(
    Drove 12 mls to test center with 10 litres of Shell V power in tank, in 4th gear down motorway for 4 miles, CAT back on a week ago plus new standard back box. ( old one broke up inside and started blowing wadding out of tailpipes! I swear it weighed 1x5 times the weight of the new one? soot filled???? )

    No 'O2' codes showing and a MOT test pass so my 'dither, hickup' at low RPM is going to require some more investigating, as it's spoiling an otherwise enjoyable 'drive' :(

    Anyone shed any light on this issue or similar experience in this 'wobble'? replies very much appreciated :bowdown:

    kev b.

  • Congratulations.

    I've always had sooty tail pipes and fuel smell. Shows rich on my air fuel guage but still has plenty of power.
    Like you I'm guessing it's the 02 sensors but as I just scrape by emmisions test
    I haven't got round to it yet.
    Maybe try new 02 sensors, a terra clean service and ecu reset,

  • Cheers Garfy1981,

    Yes mine appears on the rich side too as mentioned prev, but my Lambda of 1.001 would suggest that the O2's are functioning as desired?

    Maybe due to the CAT spending 11 months of the year on the garage floor has not done it's 'Converting' abilities any favors ? :shock: and that's what produced the raised CO of 0.120 ??? also it's only been on the car about 12 days and only covered 100+ mls prior to MOT !.

    Think CAT is stopping on car now, the noise without it produced by 'bypass' pipe, was good for a while :) but eventually became intrusive and more and more of my neighbors lights came on in the early hours of a morning as I set off for work ! :oops:

    Really like to sort this 'wobble' tho :( might have a look at EGR, PURGE, and FP solenoids and associated plumbing as it feels like somethings opening or introducing air/vacuum into induction to me when it shouldn't be? it's deffo (?) not a missfire!! and more pronounced the slower the speed of the car but always between 1500 and just after 2000 rpm and no where else in rpm range??? :?

    If I find owt, I'll report back I promise :D

    Kev b.


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