Unicarriers (& Nissan) MPLO2A25LV:
Throttle surging above idle

Hey guys. Im working on a Nissan mpl02a25lv. In the past month or so i have repaired the harness to the mas air. Flow sensor and have changed the LP converter. Now it is surging between idle and full throttle. No codes on display. Any thoughts on where to start looking?
  • Posted 22 Mar 2014 06:21
  • Discussion started by Hystertech3160
  • Arkansas, United States
Jim fultz
Showing items 1 - 5 of 5 results.
yep 15.9 is a bit high
max should be 14.8 :o)

glad it straightened it out
good deal
  • Posted 29 Mar 2014 22:46
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com
Thanks guys. Rechecked charging system. This time it was doing 15.96vdc. R&R the alternator has been good now for a couple days. Once again thanks for the input.
  • Posted 29 Mar 2014 10:40
  • Reply by Hystertech3160
  • Arkansas, United States
Jim fultz
The charging system should be putting out 13.8-14.0. Tighten your drive belt and recheck. If not then for grins and giggles, replace battery temporarily and recheck output. A dead or shorted cell can cause this issue.
  • Posted 25 Mar 2014 13:03
  • Reply by RCAV8TOR
  • Alabama, United States
What i used to do all day now takes me all day to do.
Thanks Swoop. I cleaned the throttle body & fuel controls. I then test drove it for about 30 mins with no more failure. I didnt get a call from the customer today. But i did test the charging system it was @ 13.26 vdc.
  • Posted 25 Mar 2014 12:07
  • Reply by Hystertech3160
  • Arkansas, United States
Jim fultz
the cat trucks had this same problem and it had to do with the alternator overcharging, they released a service bulletin explaining on how to check the system for this condition and repair it.

The over voltage condition was causing the ecm to over compensate the over voltage condition causing it to fluctuate the fuel controls which made the engine surge.

They said it was either caused by bad grounds on the system (engine) to chassis frame or a bad alternator regulator which ultimately led to replacing the alternator.

You may want to consider this truck might be suffering from the same problem being it is basically the same nissan system in it most likely.
  • Posted 22 Mar 2014 21:07
  • Modified 22 Mar 2014 21:08 by poster
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com

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