Possible Cause Of A Low Idle Misfire And/Or Backfire
Usage:
3400 Series Engines Equipped With An Air/Fuel Ratio Control
If a 3400 Series Engine equipped with an AFRC (air/fuel ratio control) has a misfire and/or backfire, check the diaphragm in the AFRC for damage. When these engines are operated at low idle, there is a negative boost (vacuum) in the inlet manifold. If the diaphragm has a hole in it, oil from behind the diaphragm can be pulled into the inlet manifold and then the cylinders. At low idle, this oil can cause a misfire and/or backfire. At higher rpm the engine will operate smoothly but there will be excessive (too much) smoke during rpm increases.
Caterpillar Information System:
1980/05/14 Boss Can Be Removed From Spacer Plate Cylinder Block To Get Clearance For Oil Filler Tube
1980/05/14 List Of Service Publications
1980/05/14 Changes To Oil Level Gauge Group Improve Accuracy Of Oil Level Indications
1980/05/14 Use The FT1525 Alignment Pin And FT1526 Fixture When Reconditioning Earlier 3208 Sleeve Metering Fuel Systems
1980/05/14 Turbine Wheel Shroud Design Changed; Snap Ring No Longer Used
1980/05/14 Changes To 9S240 Rack Position Tool Group; Revision To Special Instructions
1980/05/14 New 6V2120 Spline Sprocket Improves Depth Control Of 5P4175 Boring Tool Group
1980/04/30 New Liner Seat Insert For No. 1 And No. 4 Cylinders Of D353 Engines
1980/04/30 New Top Piston Ring Has Plasma-Coated Face
1980/04/30 Different Vibration Damper Now Used
1980/04/30 New 1N3270 Auxiliary Drive Group Available As Attachment
1980/04/30 Improvements Made To Water Separator Groups
1980/06/04 Improvements To Engine Oil Lines Group Makes Installation Easier; Prevents Reverse Connections
1980/06/04 New Plug With Straight-Threads Used In Engine Variable Timing Drive
1980/06/04 Improved Procedure Can Be Used To Adjust Voltage Gain
1980/06/04 Reverse Flow Check Assembly Now Used In Fuel Injection Pump Assemblies
1980/06/04 Check For Short Circuit In Rotor Field Windings If Low AC (Alternating Current) Voltage Is A Problem
1980/06/04 New Check Valve Used In Fuel Injection Pump Assembly
1980/06/04 New Cylinder Sleeve Is Available For Repairs Of Worn And/Or Damaged Cylinders
1980/06/04 New Part Available To Check The 3S1467 Plunger And Barrel Assemblies
1980/06/04 Oil Pump Drive Sleeves Now Available Separately For Parts Service
1980/07/09 6V2050 Tapered Rod Tool Group Available For Removal And Installation Of Bearings
1980/07/09 6V3075 Dial Indicator (Metric) Is Available
1980/07/09 Kysor Air-Operated Shutdown Actuators For 3406, 3408, 1693 Truck Engines