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Intermittent Hesitation Issue

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  • Intermittent Hesitation Issue


    Looking for some advice and support regarding an issue I have been experiencing for some time. Lately though it seem to be getting worse so looking to find a solution.

    So the issue I experience is that i get a very intermittent hesitation (cough) or sudden loss of power which jolts the car suddenly and then usually comes good. It typically occurs on part throttle when just cruising. It doesn't seem to be temperature related, can do it both hot and cold and when the car is warmed up or still warming up. Some times i can drive the car for weeks without it occuring and then sometimes it happens several times on a short drive. Typically it is just a one off occurance but sometimes it happens almost continously for a period of time which can be quite dangerous. I cannot find any pattern to it whatsoever.

    I have taken datalogs of when this occurs and can attach a log or snapshot of when this occurs but to summarise. What visually occurs is my manifold pressure suddenly drops and my ignition timing suddenly increases correspondingly, my TPS remains constant throughout. The injection time drops correspondingly to supply a lower amount of fuel and there is a short lag period and my AFR goes very lean. I have also logged my fuel pressure and this remains constant during the event.

    This is on an EVO 9 PNP ECU and i'm running v1.12

    So things I believe I can rule out (possibly).

    I have previously upgraded my fuel pump, problem still persists.
    I have previously upgraded my injectors, problem still persists
    I have previously upgraded my stock shared coil packs to individual coil on plug, problem still persists.
    I have previously upgraded my spark plugs to colder and smaller gap, problem still persists.
    I do not think it is fuel pressure regulator related as my logged fuel pressure seems constant.
    I have checked my cal file for any potential trims or anything like that and cannot find anything that could be causing it.
    I have tried disableing my EGR purge valve, the problem still persists.
    I have checked fuel tank for water, I had noticed some corrosion in the bottom so has had water at some point and a small amount of rust but cleaned out and has had at least 20 full tanks of both 98 and e85 since then problem still persists.
    I do not think it is a clogged fuel filter as I have no issues with wide open throttle and fuel pressure increases with boost as expected.
    I do not think it is a bad or loose connection, the problem occurs on smooth road out of the blue and when going over bumpy roads it doesn't seem to occur. I have tried re-soldering the ground connections to the ECU but problem still persists. Still not fully ruling this out though.

    I initially didn't think it was the MAP sensor because when the manifold pressure dropped it did not display the limp home table values I would expect, however I am leaning towards the sensor still functioning but providing the ECU with incorrect values intermittently. This would explain the drop in calculated fuel and the sudden lean out and hesitation.
    I am using the internal map sensor. I have taken out the ECU and checked for debris in the internal vacuum line.
    So just want to get some thoughts from others here first to rule out any other possibilities before I look at replacing the MAP sensor. Is this a problem experienced before/a common symptom that MAP sensors fail intermittently such as the way I describe?

    I understand that I could use an external MAP sensor by switching the jumper 51 and wiring the sensor to pin 92 and changing I/P manifold to external. Firstly to do this I need to buy a 4 bar map sensor, are there any preferred brands? I currently run around 26psi boost. Secondly my ECU plug actually does not have a pin 92 wire. I would need to repurpose an unused wire such as pin 61 or 62 by removing the pin and placing it into the pin 92 position and splice into the harness in the engine bay and run that to my map sensor which I would place as close to the manifold as possible. I am leaning towards the Link 4 bar sensor which has a barb to easily run a vacuum line to.

    The other potential option is to try and replace the internal map sensor to see if this fixes the problem. From opening up the ecu box to check the vacuum line for debris, I found the sensor model as MPX2200AP and K0648DE. It is soldered in place. Is this a job which one could do at home if they are handy with a soldering iron? If so, i have found a few MPX2200AP sensors online but none matched the K0648DE version, does this matter so long as it is the MPX2200AP. Is there anything else you must do?

    As mentioned previously before I go down either of these two paths however I just want to rule out anything else which I have potentially overlooked.

    Thankyou in advance.


  • #2
    This looks like a failed map sensor. The usual cause is hose routing into ecu map sensor causing condensation to run into the map sensor. Pull the box, send to Autronic in Australia and get it repaired
    He gets his lap dogs to do his talking for him. Buzzard is a good example.


    • #3
      Thankyou for confirming my suspicions Chris.

      Now that you mention the condensation, it makes sense and I think this is what did kill my sensor.
      I noticed some white residue inside the vacuum line within the ecu to the internal map sensor when I was checking for debris blocking the line. I didn't think anything of it at the time but this does look a lot like a water mark.

      So to prevent this in the future how should I best run the vacuum line? Currently it comes straight from my intake manifold travels down through my firewall and runs along with my harness to the ecu then up to inside the ecu. There is a bit of a U shape to it, so rather surprised it would travel upwards like it appears to have done. Is it a case of just occasionally pulling off the vacuum line and draining any moisture periodically?

      Also I have contacted Autronic support for sending my ecu for repair.



      • #4
        I would fit an engine bay mounted map sensor and use the ecu mounted map sensor for constant Baro update. The improvements in response time would be worth it alone. You are my final support task on this forum so feel free to grab my phone number off the Autronic dealer list or and I can advise the setup. 26psi could be accommodated by a Bosch 3 bar t-map sensor mounted in a holder.
        He gets his lap dogs to do his talking for him. Buzzard is a good example.


        • #5
          Yes agree, I think I will go down this path, it eliminates risk of condensation killing the internal sensor again and the response improvement as well.
          Appreciate the help Chris, I may contact you in the future for configuration once I get this all setup in the car.


          • #6
            No problem. Email is best. Get the ecu to Autronic and get it sorted. Let me know. Your issue is my final support task on these forums so I hope we saw you out in style.

            Best Regards from your dealer support team.

            Chris and Ian.
            Last edited by Chris; August 7th, 2020, 09:18 PM.
            He gets his lap dogs to do his talking for him. Buzzard is a good example.


            • #7
              You sure did, thanks again, appreciate both yours and Ian’s help in the past as well.
              Kind regards,


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