Spark Plugs - Replaced
Plug Wires - Replaced
Coil - Will inspect
Fuel Injector - Will inspect
Vacuum Leak - inspected and fix one suspect, rest look good.
EGR valve - Replaced
Carbon on the intake valves - I have been using injector cleaner for two tanks fulls now.
Flat cam - ? will research
Oxygen sensor - Replaced both about 20k ago.
Fuel pressure - Measured in low 40'*
Engine mounts - Inspected, look good.
Axle joints - Will inspect.
TP Sensor - Will inspect / replace.
Cylinder balance - will remove and inspect.
Fuel contamination - Mobil 93 Octane only.
* Spark plugs - Inspect for cracks, high resistance or a broken insulator.
* Plug wires - Look in each end. If there is red dust (ozone) or a black substance (carbon) present, then the wires are bad. Also look for a white discoloration of the wire. This indicates arcing during hard acceleration.
* Coil - Look for a black discoloration on the bottom of the coil. This indicates arcing while the engine is misfiring.
* Fuel injector - The filter may be plugged.
* Vacuum leak - The engine will not get a correct amount of fuel. The mixture may run rich or lean depending on where the leak occurs.
* EGR valve - The valve may let in too much or too little unburnable exhaust gas and could cause the engine to run rich or lean.
* MAP/MAF sensor - Like a vacuum leak, the engine will not get the correct amount of fuel for proper engine operation.
* Carbon on the intake valves - Carbon restricts the proper flow of air/fuel mixture into the cylinders.
* Flat cam - Valves do not open enough to let the proper fuel/air mixture into the cylinders.
* Oxygen sensor - This sensor may command the engine too rich or too lean for too long.
* Fuel pressure - This may be too low.
* Engine mounts - Vibration of the mounts can be multiplied by TCC engagement.
* Axle joints - Check for vibration.
* TP Sensor - The TCC apply and release depends on the TP Sensor in many engines. If the TP Sensor is out of specification, TCC may remain applied during initial engine loading.
* Cylinder balance - Bad piston rings or poorly sealing valves can cause low power in a cylinder.
* Fuel contamination - This causes poor engine performance.