250 Missfire count rising on throttle lift off + high knock counts?

Discussion in 'Mechanical - Engine, Gearbox, Exhaust etc' started by CaptainHavok, Aug 29, 2019.

  1. For the last years I've been hunting for a intermittent fault where my engine cuts out aggressiveley (possibly boost cut or some torque limiter). More info on that is in this post: https://rsmegane.com/threads/intermittent-power-loss-engine-cut-missfire.14706/

    Now I've upgraded the Torque app abit and found some irregularities, missfire count goes up into the hundreds after a 30 minute drive. However, it only counts the misfire on throttle lifts into engine braking or shifting - and especially at low rpms. No missfires felt/heard or any seeming loss of power.

    Knock counts are also high (attatched screenpic show historic values) and there is one cylinder that is significantly lower than the other ones. Cylinder four is significantly higher. Accounting for mileage of the car I get approximatley one knock every 20km or so, and the numbers seem to be rising at that rate.

    My question is: shouldn't off throttle misfires be impossible? Are missfires counted using the TDC/crank sensor - and if so, could it be faulty? Could it be that the car drops a bit of fuel to make the pops and bangs that throws it off? (on standard map).. Or could there be a problem with crank case ventilation which affects crank speed on throttle lift?

    Other known variables:
    1. Front o2 sensor heat shielding has dried up and perished, didn't think it would affect much but I did get some wierd readings last night. Will keep monitoring.
    2. Coolant temp sits comfortably between 80-84 degrees Celsius. Which seemed low but from what I've read the thermostat should open at 83-84 degrees?
    3. Throttle opening on cold start idle is 17%, and on warm idle slightly below 14%
    4. Running an ecu test i get a "fail" on "catalyst monitor bank 1" (secondary o2 sensor?) but I'm unsure what the Count represents. (see second screenshot)

    No other known issues, gas mileage very acceptable for my driving style.

    Screenshot_20190827-173807_Torque.jpg Screenshot_20190828-084825_Torque.jpg
  2. *Correction* obviously cylinder 1 was the one with the higher knock count..
  3. Have you had the injectors checked, the high knock count is not a good scenario
  4. I have not, is it something that can be tested by the dealers or is it simply a replacement item? and do i need to have a look at fuelpump and fuelfilter in that case?
  5. Try and concentrate, or get someone to look more closely at what your short term fuel trim and o2 sensor precat does while accelerating, what are the readings?
    Say in 2nd gear just welly it then let off and brake.
  6. Test both o2 sensors with your torque app, simulate a rich condition by spraying propane or brake cleaner in your intake after the maf at the inlet manifold, see if the o2, s react?
    Or simulate a weak condition by just pulling of intake hose at manifold, look for reaction from o2, s, if they react they are fine, at least rules them out!
    Precat o2, s should fluctuate from 200 millivolts to 800millivolts,post cat should be steady around 450millivolts from memory?
    Try running car with precat o2 removed, if it runs better cat might be partially blocked. Think you mentioned once after cat o2 showed a fault?
    Above tests will rule out o2, s.
  7. Thank you for your guidence! Will run some tests tomorrow. Did get some wierd O2 readings at warm idle today again. Moved the sensor wire by hand and the swings made more sense but I don't know if moving the wire was the reason. Last screenshot is after I moved wire.

    Simultaniously I think i heard a scraping or something noise on belt side of engine. Made video but cellphone is dead so will try to get it up tomorrow aswell. Cylinder 1 misfired on idle (misfire count on cell, noticed nothing).

    Thank you again :smile:

    Attached Files:

  8. Another thing, if there's a misfire on cylinder 1,swap that coil over to cylinder 2 then put cylinder 2,s coil over to cylinder 1.If your misfire now shows on cylinder 2 on your torque app you know cylinder 1 coil is bad!
  9. If you have a decent mapper near you then you g through a remap process will tell you the issue you will be able to get a wideband connected and see what's happening and also see fuel duty for each cylinder as well as checking knock and ignition.
  10. Thanks for the tips Arch. There is a decent mapper however I'm not sure they've worked on meganes before? Maybe that isn't so important for theese purposes. Closest RS specialist is in another country.
  11. Perhaps you could speak with both tuners so you can get a data log sent across to the renault specialist? Then he can advise what's going on?
    CaptainHavok likes this.
  12. First off these meganes are a nightmare to map and even rs tuning had a problem mapping my 1st 230 causing a boost cut and limp mode after a map way back in 2007 albeit it was the first 230 he ever mapped and never had a problem with anything they mapped since but someone who had never worked with the meganes before could also have problems, so suspect the map before anything else. Secondly check the timing is correct as cheap tools when changing the timing belt can cause timing issues and also so could also cause your fault.
    CaptainHavok likes this.
  13. yes there's at least one nasty setting in reno generic map that need switching off as it doesn't come into play on rolling road but does when live driving, deffo need tuner that knows reno ECU well
    CaptainHavok likes this.
  14. First off, thank you everyone for your insights! Been going at it alone, just feels good to have some new paths to pursue

    Haven't been able to tinker with it today as i'm dealing with some issues with the ticker simultaniously. All day at the hospital..

    Did however call my service guy at renault and asked him if he saw something in the software when i had it in for cambelt service.

    He said it did show that the software was not standard so I'm guessing it's tuned.

    Had a reciept in the car from tuner but figured it had been returned to standard since max boost was 1150mbar which i believe is standard max for a 250?

    Anyway, have some parts to swap but, next on order is possibly o2 sensor and hopefully a return to stock software if the ecu isn't locked. (Tuner went out of buisness so in that case i'm screwed)

    If that doesn't work I'll have a look at the fueling bits.

    Thanks again!
  15. If it is a poor tune the irony in that I've wanted an rstuning map for years, but put it of because i didn't want to tune a poorly running car is going to stay with me a while btw..
  16. RS tuning will defiantly lock your ECU, caused me no end of problems.
  17. Charlie Howard

    Charlie Howard RSM Club Member

    How did you get Torque to detect misfires? Mine can't do it
  18. I Think i could use the vehichle diagnostic function at the end of a journey to view a summary of all missfires with Torque PRO. To get the individual cylinders i had to download an addon called "Advanced EX for RENAULT", it has some extra PIDs you can install. Choose the Laguna III 2.0 (M4R) Engine, which isn't exactly the same but i guess it's the closest.
  19. Charlie Howard

    Charlie Howard RSM Club Member

  20. Charlie Howard

    Charlie Howard RSM Club Member

    Here's mine, very similar to yours. Rises on lift off, I'm guessing either all cars have misfires as it drives perfectly or the software doesn't work for this car correctly. If others could try it that would be good
  21. The misfire there could technically be because of the pops and bangs? Last time I tracked the misfires on mine it also had misfires on lift off.

    I don't know enough to say
  22. Charlie Howard

    Charlie Howard RSM Club Member

    Possibly, I did get maybe 1 or not from normal driving though. I'm thinking all cars get minor misfires because they weren't noticeable at all. My old 225 had a major misfire that brought the engine light on and jolted the whole car. I wouldn't have known mine had any without it
  23. Wow, thanks guys!

    Feel a little bit better knowing I'm not alone then :smile:

    Haven't had much chance to fiddle with the car theese few weeks, but i did gap the plugs down to 0.6mm, no change in missfires but the car did feel slightly better at the top revs, max boost did increase to 1200mbar too. not sure what to make of that really, was hot as balls though so might be why.

    Car going into storage for wintertime now so won't have time to map it or swap that o2 sensor. But i will dig up this thread and update on any success or failures next season.

    Thanks again for the support guys :smile:
  24. Charlie Howard

    Charlie Howard RSM Club Member

    Any news on your issue?
  25. Yes! It would seem there was a few things. The knock counts where reduced to half by changing from 5w-30 oil (poured in there by dealer) to 5w-40. Even the knock count i had though was not enough to warrant any concern i was told. Guessing some of it could have been phantom knocks by noisy valves? Maybe.

    The harsh engine cut was a bad map by a swedish tuner, got a new one from henk and it hasnt happened since. He had also seen the fault code before (DTC 061A). Also gained about 40nm and 25 hp which was welcomed!

    Stuttering on cold idle and missfires on throttle lift of i am suspecting is just a caracteristic of this engine? Anyways. Car runs absolutley fantastic at this point so not too worried about it.

    Will update my other thread once i'm 100% the cut out failure has been all sorted.
  26. Charlie Howard

    Charlie Howard RSM Club Member

    So you still get knocks just not as much?
    I spoke to K-Tec about it, they said it's pretty normal. There's sensors that detect the knock but they can be set off by a lot of stuff like bumps in the road
  27. Exactly. Honestly i dont think there is any need to worry unless you get several knocks in a quick succession. They are essentially just responding to a frequency so anything that gets to them at that frequency will register.

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