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Misfiring problem

cnasrcnasr Posts: 4
edited June 2015 in Cadillac
I have a problem with my CTS 2005 3,6L that occurs randomly and can be described as following:
When speeding up, the engine starts hesitating and the check engine light will become blinking. Some times this symptom appears when starting the engine and in idle situation.
I consulted a mechanic scanning the engine and he told me that it's a misfiring problem on 2 cylinders (1 - 5) reporting this issue to the ECM itself and suggesting to replace it without checking the related spark, coil, wiring,...

Can I ask your advice please if should I replace the ECM or it may not be the cause of this misfiring problem?

Appreciating your answer

Thanks

Comments

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,457
    We'd have to know, first of all, what trouble code or codes the mechanic found with the scan tool and what motivated him to claim the ECM was bad.

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  • cnasrcnasr Posts: 4
    I have a problem with my CTS 2005 3,6L that occurs randomly and can be described as following:
    When speeding up, the engine starts hesitating and the check engine light will become blinking. Some times this symptom appears when starting the engine and in idle situation.
    I consulted a mechanic scanning the engine and he told me that it's a misfiring problem on 2 cylinders (1 - 5) reporting this issue to the ECM itself and suggesting to replace it without checking the related spark, coil, wiring,...

    Can I ask your advice please if should I replace the ECM or it may not be the cause of this misfiring problem?

    Appreciating your answer

    Thanks
  • cnasrcnasr Posts: 4
    The codes was: P0301 - P0305
    About the mechanic claim, it was simply based on previous problems with same car model, and he told me that usually the ECM will be damaged after this milage (180 000 M)
    He didn't check any other component.
  • cnasrcnasr Posts: 4
    He said also: as the problem is occurring randomly, it should be caused by a software malfunctioning inside the ECM and not a hardware electrical issue (spark, coil, wire,...)
    is it true and should I go for an ECM replacement which will cost me about 750 $ ?
  • thecardoc3thecardoc3 Posts: 4,957
    There isn't enough information here to make any kind of recommendation. Each repair event should always be analyzed by what is occurring on that particular car at that point in time. Is the PCM losing the ability to fire the coils when the misfire occurs? Do you have scope captures where the technician was using a low amps probe and captured the current waveform from the system both when the car was running correctly and during a failure event? Was full pinpoint testing done to ensure that there isn't a wiring harness issue actually causng the misfire?

    A solid routine requires that the shop/technician actively troubleshoot the system while a failure is occurring, but this isn't universally supported. There is tons of pressure by consumers for shops to not charge for diagnostics and there is no shortage of people who not only condemn a shop for taking a scientific approach they actively preach that you should be able to just google the symptom and that will tell you what part to replace.

    There is no magic machine that someone can connect to the car that tells the tech what s wrong. It quite often is labor intensive to do proper diagnostics. It also requires that the technician have a good game plan for and most of all knowledge and patience to diagnose a lot of the problems that cars present with. The consumer pressure to not charge for diagnostics makes learning to be that diagnostic technician a very difficult career choice. It seems there is always the next person in line who expects that techs will just know the answer to a given symptom. Based on only what you have written here it cannot be ruled out that this technician is succumbing to that pressure and just going with instinct instead of testing and proving what is wrong. That is the wrong approach, no matter how much pressure media and consumers try and put on the techs to lessen the repair expenses. If this hasn't been truly tested completely then you should not be replacing the computer yet. The catch is he could be correct and now testing correctly usually gets treated like it was a wasted effort and even a rip-off if it proves that the PCM itself is to blame.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 23,163
    edited June 2015
    My 3800 leSabre is giving an infrequent misfire. Here are 2 of the 3 front plugs. There's a layer of deposit on the corner of the porcelain of all 3. Is this causing a misfire when engine is fairly warm and the throttle is tipped in from idle? or when having driving with very light throttle and then tipping in to add a little power? 2003, 197,000 miles. About 30,000 on the plugs.



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  • thecardoc3thecardoc3 Posts: 4,957
    "Is this causing a misfire when engine is fairly warm and the throttle is tipped in from idle? or when having driving with very light throttle and then tipping in to add a little power"

    First when watching the misfire counter in the live data stream, which cylinder(s) were reporting the misfires?
    The engine load that you are describing would cause high secondary spark demand voltages, so if the spark could leak anywhere that is the condition that it would be likely to first occur. But you need to confirm the misfires with the cylinders that are affected and then start investigating for causes. Those deposits alone would not be enough to confirm as a cause especially because double platinum plugs are very resistant to in cylinder issues. It would be far more likely for the plug wire boots to be degrading and for carbon tracking due to micro scratches on the porcelain plug from the plug boots to become conductive and allow the spark to be jumping outside of the cylinder.

    BTW, with the tendency to promote external spark leak issues because of how high secondary spark demand voltages are these days, just taking the plugs out to inspect them actually commits you to replacing them and the plug wires or else you are likely to cause a misfire to occur when there wasn't one before.
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