Surging Idle when Cold. Discussion about troubleshooting Doosan

Doosan GC25E-5:
Surging Idle when Cold

I have completely replaced all hoses from the regulator, to the dither valves, to the carburator, I have swapped the o2 sensor, the mixer(with throttle body and electronic throttle control), i have swapped the regulator and dither valves(dither valves were bad, I have new ones on order). and now my truck surges/lopes during idle untill the truck warms up. The truck also has new spark plugs, PCV valve rattles/blows through only 1 directions and has great vacuum when hooked up. As stated in other threads, If i unplug the wire harness from the dither valves, the surging goes away. Please Help!! (this all started with a code 771 and dither valves you could blow through)

Posted 3 Oct 2018 02:11
Modified 3 Oct 2018 02:12 by poster
Discussion started by MuddyForks
Illinois, United States

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Also make sure the plug gap is correct. Doosan requires.035-45, often the new platinum plugs from dealer are gapped to.060 and this can cause rough idle.

Posted 12 Oct 2018 00:23
Reply by tom_p
Alberta, Canada

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Check vacuum hose brass fitting to the mixer assure the fitting orifice is not plugged Change the PCV valve.
Woodward fuel system runs very lean so any change in vacuum will
trip a fault code.

Posted 5 Oct 2018 02:04
Reply by tom_p
Alberta, Canada

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