Legend Coupe V6-3206cc 3.2L SOHC FI (1991)
Piston Ring: All Technical Service Bulletins
Engine - Cold Engine Knock
March 23, 1993
BULLETIN NO.
93-006
YEAR
1991-93
MODEL
LEGEND
VIN APPLICATION
See VEHICLES AFFECTED
Cold Engine Knock
SYMPTOM
A metallic knocking noise is heard at 1,200-1,500 rpm when accelerating lightly right after a cold start. This noise disappears when the engine reaches
normal operating temperature.
PROBABLE CAUSE
Carbon buildup in the piston ring land causes the ring to bind, allowing the piston to slap against the cylinder wall.
VEHICLES AFFECTED
Sedan
1991: All
1992: All
1993: thru VIN JH4KA7... PC005500
Coupe
1991: All
1992: All
1993: None
DIAGNOSIS
Use GM Top Engine Cleaner (see REQUIRED MATERIALS) to determine it the knocking is caused by a binding piston ring.
1.
Disconnect the No.21 hose at the base of the throttle body.
2.
Connect a long hose to the throttle body base.
3.
Start the engine. Keep it running at 800-1,000 rpm, then place the hose in the Top Engine Cleaner. Run the engine until the can is empty, then
immediately shut it off.
4.
Reinstall the No. 21 hose. Let the car sit for 1 to 2 hours.
