Mitsubishi FGC30:
#1 cylinder misses after high rev.

First let me thank Justinm for all the info he provided with the Hyster ev100 problem I had.
Ok here is a good one that I hope someone has seen before. Mitsubushi fg30 with a 4g64 engine. This unit starts and runs perfect until you rev the engine for approximately 15-20 seconds. At that point the engine begins to miss on #1 cylinder. If the engine is returned to idle, it will then miss for 15 seconds or so and then gradually begin to fire and then resume running perfectly. Have done a thorough check of the ignition system and cyl does not loose spark and plugs are new. compression test was over 200psi. My last "guess" was that the valve lash adjusters for that cylinder were collapsing and loosing lift on the valve. Had a valve tapping right after reving so we replaced all lash adjusters/lifters. This made no difference except the tapping is gone after high revs. OK GUYSLET ME HAVE IT. WHAT HAVE I MISSED?
  • Posted 9 Apr 2009 00:52
  • Discussion started by rrlift
  • Illinois, United States
Working so I can ride.
Showing items 1 - 8 of 8 results.
Thank you very much for getting back and letting us know what it finally was.
  • Posted 18 May 2009 03:45
  • Reply by edward_t
  • South Carolina, United States
"it's not rocket surgery"
After trying many things, tore engine down and found rings to be extremely worn or wrong rings installed onto.050mm over pistons. #1 was the worst. ring end gap was.130". after rebuild engine runs great.
  • Posted 18 May 2009 00:17
  • Reply by rrlift
  • Illinois, United States
Hello, I would automatically change the cap, rotor, plugs and wires. They are cheap to replace and would save second guessing yourself. I have had new parts fail on me, witch is fun to troubleshoot. ( Spark plugs get dropped in the parts room) How many hours on the engine??? These engines are very good, never really had any engine trouble except for VERY high hour machines
  • Posted 9 Apr 2009 22:46
  • Reply by Prentice
  • Ontario, Canada
af13d should be a 2003, sg15 CARB system.
a few possibilities, any side way free-play in the distributor shaft? at all? not up and down, but side to side?
how long is the vacuum hose that runs to the ECM from the throttle body? (NEEDS to be at least 29 inches maybe as long as 34'), which looks way too long, but unless the ECM has been replaced with the newer version, this hose is "tuned" to a vacuum loss due to it's length. the newer version does not use the vac hose, and the plug for the hose is capped off inside the ECM)
Next would be to insure the vac hoses on the throttle body are in the correct places, with the hose that runs to the Dist. for vac advance is in the top and the one to the ECM is in the lower (more towards the manifold) placement.
next, I would put a timing light on the thing, and see if the timing is advancing as it should when you increase RPMs.
  • Posted 9 Apr 2009 20:50
  • Modified 9 Apr 2009 20:51 by poster
  • Reply by edward_t
  • South Carolina, United States
justinm,
SN:AF13d30***. Installed new plug wire and plug on bad cylinder. Did not check valve stems for wear, but stem tops were not worn past origional surface. Will look deeper into valve guide wear.
  • Posted 9 Apr 2009 14:28
  • Reply by rrlift
  • Illinois, United States
Working so I can ride.
Determined @1 miss by removing plug wire. will try fuel fix.
  • Posted 9 Apr 2009 14:16
  • Reply by rrlift
  • Illinois, United States
A couple questions:
How did you determine it's #1 that's missing?
Isn't that a overhead cam motor with solid adjustable lifter/rockers, how can they collape?

If it's propane fueled, try to rev it up and make it start to miss then quick shut the tank off. If it immediatley shuts down then it has a fuel flow problem.
  • Posted 9 Apr 2009 04:46
  • Reply by mrfixit
  • New York, United States
what is the 1st part of the serial number?
does this have emission controls?

that engine should have 163 PSI with all the plugs removed and the throttle plate blocked wide open

did you swap the plug wires and cap for new?

did they check the valves for wear?
  • Posted 9 Apr 2009 01:55
  • Reply by justinm
  • New York, United States
New York, New York its a heluva town..you know that The Bronx is up..and I'm Brooklyn down

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