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1G Misfiring when on idle and letting off throttle.


Probationary Member
Sep 1, 2019
Manila, Asia
Car runs fine under load, and even when you start it for the first 5 or so seconds when idle is high, When idle settles at around 850 you can really feel the engine vibrations and misfire.
The Galant is running and driving but the vibration is extremely worrying, at stop and go traffic the idle is really terrible and it sounds like its running at 3 1/2 cylinders, when driving and letting off the throttle, you can also hear the misfires. idle also drops at traffic but ive never experienced it stalling out at traffic

Backstory on how the problem started:
It was running great before but due for Preventive Maintenance, I cleaned the Injectors, TB, IACV, EGR, MAF and other sensors, changed BISS screw gasket, changed plugs with correct gapping, retorqued the head, replaced belts and pulleys. I replaced Timing Belt A and B (for the balance shaft), while adjusting the timing, I noticed that the oil pump sprocket is not moving freely, I really have to turn it with force to adjust it. Since I can't use the method where the oil pump sprocket falls freely to correct the balance shaft position, I went behind the block to insert a screwdriver to ensure the balance shaft was adjusted correctly. All timing is correct since I repeated this process 3 times already trying to fix misfiring issue, Tension for the belt is also correct.

Could it be that the oil pump sprocket not moving freely be causing the problem and misfire? The balance shaft was already making a knocking noise before and I was already planning on doing a Balance Shaft Delete.
NO CEL on gauge, Engine is 1g 4G63 NA
Any suggestions would be appreciated


Proven Member
Dec 9, 2010
wampum, Pennsylvania
You would need to disconnect the front one and leave it in there or remove it and spin the bearings around to block the oil holes and the rear one you would need to remove it in pieces by cutting it up as you pull it out or remove the engine to completely remove it in tact, you then need a stub shaft for the oil pump.


Proven Member
Jun 16, 2019
Hull, Georgia
I got the STM balance shaft elimination kit but the bearings truthfully werent that great and each one split where the bearings are connected to each other and I ended up using the original bearings but turned to block the oil passages. That is if you go that route.
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