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2018 MD115A2 Hard start, rough idle, high rpm

BryanR1

New member
2018 MD115A2 <br>Progressive problem started with a hard start.  While cranking, the engine will fire and cough white smoke intermittently. After multiple tries it will start with a cloud of white smoke and rev to a high rpm.  Comes back to idle 800 rpm. It ran fine through all rpms. After shut down it will start fine if you started it within 15-30 minutes.  After sitting longer than 30 minutes the same hard start process.  This has been doing this for the last four outings with multiple stop and starts while fishing.<br><br>Problem has progressed to hard start, rough idle, running around 1200-1600 rpm it runs rough and almost stalls, bump it up past 2000 rpm it will stable out and run fine. Bring back down to idle and it idles fine with no misses while waiting our turn to at the boat launch over 10 minutes in and out of idle. <br><br>On muffs in the driveway.  No hard start, idles fine until holding throttle around 1200-1600 it'll start missing and wants to stall, now bump above 2000 rpm, it's missing with erratic rpm fluctuating up and down when trying to stay at a set rpm.  When throttling down to neutral, it will stay reving above 2000 rpm missing with erratic rpm. Sometime it'll come back down to idle, but idle rough. Other time have to turn key off to get rpms down.  Immediate restart it'll idle, but rough and will continue the same process when throttling to 1200-1600.<br><br> On the muffs I've had it start as normal and idle for over 15 minutes and throttle straight to 2200 rpms and leave it there for 5 minutes with no issues at all.  Drop it down to 1200-1600 rpms for a bit and the above process repeats itself. Pulling plugs resulted in #1,2,4 half the ceramic is brownish white and other half black. Also slightly wet.  #3 plug brownish white and dry.<br><br>Coils ohm test ranged from .7-.8 and 14.29-14.6<br>Fuel injectors 37001  ohm test from 2.3-2.4 also applied 12v, heard clicking and fuel would come out exhaust<br>Air injectors ohm test 1.8 all four<br>TPS closed 4.7, 4.8, .8, .79<br>TPS wide open 4.6, 4.8, 4.2, 4.3<br>Air rail psi 100<br>Fuel rail psi 110<br>compression all four 120 psi<br><br>Self diagnostics:<br>1.  100-200 hours<br>2.  battery voltage low once<br>3.  air compressor cooling water abnormally high <br>     cooling water temperature was once high (prior owner)<br>4.  air compressor cooling water temp high<br>     cooling water temp was once high (prior owner)<br>5.  oil was once low (prior owner)<br>6.  CPS malfunction<br>     wire was once broken/CPS malfunction<br><br>I have cleared all codes to see if CPS malfunction would come back, it has not. No other codes have come up either.<br>I have done an ECU/TPS reset.<br><br>Thankful for any help.<br>Bryan
Forgot to add CPS ohm and gap were good.
 
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I would start by double checking all connections, especially all grounds. See is any more codes come up.
 
Paul, thanks for the response. I rechecked all grounds. Nothing loose or corroded. Ran diagnostic again: 2000 rpm with battery light (100-200 hours)? 6200 rpm with battery light. The manual that I could find shows that it's a 2007 publication. There is no diagnostic for 6200 rpm. I'm hoping that it correlates to the 2007 manual at 6000 rpm with battery light (#2TPS malfunction/wiring was once broken or a component once malfunctioned).
Again thanks for your response, I would not have run the diagnostic again.
 
Cleared codes and reset TPS. Ran on muffs. No codes after recheck. On muffs same results, rough through idle to 3000 rpms. Bump from idle it will jump to 2000 rpm, won't hold below 2000 rpm without continuous throttle adjustment. Holding rpm above 2000 it will surge +/- 100 rpms. Turn off and restart it will jump to 1800-2000 rpms and hold while in neutral, must turn off to get rpms down. This is intermittent, other restarts it will idle rough at 800. Engine is running rough the whole time. Did not stall on muffs.
 
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I got the 2000 and battery light before going into mode 3 for diagnosis. Manual says the engine has between 100-200 hours. When the weather clears up I'll run it with a load and see if any codes come up. After that I'll inspect the injectors. Thanks for the input.
 
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