1989 Jeep Cherokee XJ Pioneer Renix 4.6L I6 AW4 NP231 6" RE Lift 35"x12.5" KM2s
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A few things to looks for if your engine is making noise:
- Exhaust Manifold Leaks
- Loose Flexplate bolts hitting bellhousing
- Cracked Flexplate
- Damaged Spark Plugs
- Damaged Valves / Valve Seats
- Worn Valve Guides
- Broken / Worn Piston Rings
- Bent / Broken Push Rods
- Binding / Cracked Valve Springs
- Worn / Stuck Camshaft Lifters
- Flat Camshaft Lobe
- Worn Cam/Crank Bearings
- Piston Slap
Tests you can try:
- Slow Motion Test: With the Valve Cover off, film your engine, preferable with a slow motion setting (60fps, 120fps, 240fps, ect) and slow it down on a computer to better see what the engine is doing and what the sound actually sounds like.
- Timing Light Test: Count how often the noise happens compared to a spark plug firing. 1 tap for 1 blink is half engine speed (Camshaft or Valve Train related) 2 taps for 1 blink is full engine speed (Crankshaft or Rotating Assembly related)
- Elimination Test: Disconnect the Spark Plug wire and Injector wire from 1 cylinder at a time and start the vehicle to listen for a change in noise. Go down the line for each cylinder to see if you can find the culprit; this may narrow it down to combustion related issues.
- Compression Test: Using a Compression Gauge, pull all spark plugs and check each cylinder's compression. An abnormally low reading points to a cylinder not sealing properly.
- Leak Down Test: If a Cylinder shows low compression, turn the crankshaft until that cylinder is on Top Dead Center (TDC) on the Compression stroke and connect a low pressure airline up to the spark plug hole. Try to listen to where the air is coming out. Listen to Intake, Exhaust Pipe, Crankcase, and check coolant for bubbles.
- Camshaft Lift Measurement: Using a dial indicator connected to a pushrod, measure the lift of each Cam Lobe to check for severe wear.
- Lifter Preload Measurement: Check to see if Camshaft Lifters have proper preload. Can be measured, or loosen up rockers for one cylinder to see if noise gets better or worse.
- Worn Rod Bearing Test: Rotate the Crankshaft until the Cylinder in question is starting to move down, then insert a screwdriver into the spark plug hole so that it touches the piston. Push down sharply on the piston and listen for a knock which would indicate loose clearances on the Rod Bearing.
