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[Web Creator] [LMSOFT]
VK Commodore Engine Issues
Phoenix Mechanical
Soaring

Air pump - As part of the Emission Control System, Carburetted 3.3ltr VK's have a belt driven air pump to recirculate exhaust gas back into the combustion chambers. These pumps sieze, and it is quite common to see them either missing, or the belt removed. Ideally they should be replace to comply with ADR's.

Cam gears - Original cam gears are made of composite fibre and mesh against a metal crank gear. The fibre gears are renowned for stripping teeth, and when this occurs the engine stops. If a cam gear's teeth have stripped, the rocker gear will not move while the engine is being cranked (The rocker gear can be observed through the oil cap hole). New gears are available, either in fibre or alloy. Alloy gears are more durable, but usually produce more noise compared to fibre gears.

Distributor gear - Distributor gears are originally nylon, and can and these gears can sheer. When this happens the distributor shaft can be rotated independently, or will not turn when the engine is being cranked. New gears are available.

Camshaft - Major problems can arise when a cam lobe is worn down, as insufficient lobe lift will restrict valve opening and therefore cylinder operation.

Rocker gear - Rocker gear wear is inevitable. Alloy rocker bridges and steel rockers arms wear with age, and wear increases noise and reduces valve lift. New rocker arms and bridges are available.

Rear Main seal - Commodore rear main seals are rope, and these rope seals squeeze against the crankshaft at the rear of the engine. Hot engine oil and age reduces the seals ability to work effectively, and this results in an oil leak from the back of the crankshaft. To replace the rear main seals the crank needs to be removed from the engine, which usually means that the engine needs to be out of the vehicle. Some tools (Sneaky Pete by Lisle) are available from auto parts stores, which are used for removing and replacing the rear seal with the crank still in place, but are not always successful.

Inlet manifold 6cyld - On a standard engine the inlet manifold is bolted to the exhaust manifold, and they are both bolted to the head. When together, the manifold faces are machined flat to ensure adequate sealing against the head. The inlet and exhaust manifolds expand and contract at different rates because of their different metals, and over time the manifold faces may distort and require re-machining or even just a simple retension. A distorted or unsealed manifold can cause erratic engine idling and/or low vacuum.

Extractors EFI - VK EFI engines cam standard with stainless steel extractors. A common area of failure is cracking of the joint of number 1 primary pipe and the first collector. Repairing the extractor is usually cheaper than the cost of a new set.

Vacuum advance unit V8 and EFI - Vacuum advance diaphragms are bolted to the distributor and advance engine timing during acceleration. The rubber diaphragm can split which results in loss of timing advance and therefore loss of power. These diaphragms are no longer available and are usually not separated from second hand distributors.

Harmonic balancer - Harmonic balancers usually consist of inner and outer hemispheres which are located together by vulcanized rubber. Over time the rubber perishes or loosens and the outer hemisphere can move freely of the inner hemisphere. A few problems arise here, one being the danger of damage from loose parts, and the other being the loss of timing position which is located on the outer hemisphere.

EST Sensor - VK 6cyld EST (Electronic Sensor Timing) use a crank position sensor, a basic style of throttle position switch and an EST computer. The crank position sensor registers the position of the crankshaft by 3 magnets on the flywheel (manual) or torque converter (automatic). These sensors do fail either internally or by physical damage, and can be the cause of starting or revving problems. Diagnosis of EST systems can be difficult due to their lack of inbuilt diagnostic abilities like later systems.
Conrod and pistons - 6cyld black motors are renowned for conrod bearing failure and piston skirt failure (cracking). Either problem results in engine noise and eventually failure, and requires the engine to be dismantled to repair. When released, many VK's where recalled to replace #1 conrod bearing because of incorrect clearances.

Throttle body EFI - All throttle bodies are preset when assembled, and usually do not require adjustment. These throttle bodies use an IAC (Idle Air Control) circuit, which bypasses air past the throttle body butterfly and maintains a regular idle speed. Over time, the IAC port carbons up and restricts air flow which restricts idle quality. To correct this problem, the throttle body should be removed, thoroughly cleaned and reset to factory settings if required. Some repair places tamper with the base idle screw to compensate for poor idle, but this is incorrect and can create further ptoblems.

Air Flow Meter EFI - Air flow meters us a swinging door attached to an electrical potentiometer, which sends a signal to the ECU (Engine Control Unit). This signal is used to interpret how much fuel is delivered by the injectors as the air flow changes. The air flow meter door can be damaged by backfiring, especially on LPG systems. The potentiometer can fail due to moisture or through electrical failure. Change over items are available.

V8 Exhaust butterfly - Between the right hand exhaust manifold and front engine pipe is an exhaust preheat butterfly, which apparently was designed to reduce engine warm up time by restricting exhaust gas flow when cold. The butterfly seizes, sometimes open, sometimes closed, and when closed, engine power can be reduced dramatically. Sometimes the housing of the exhaust butterfly cracks, which results in an exhaust leak, which can also be responsible for engine power loss.

V8 Fuel filter - Most early Commodores did not have an external fuel filter fitted, as they relied on the fuel tank sender unit sock to trap dirt particles. As the quality of our fuel has decreased, the need for an external replaceable filter becomes very important.

V8 Idle - Most V8's should have an idle solenoid on the carburettor, which is externally adjustable. In many cases solenoids are not adjusted correctly, and the idle adjustment has been done with the throttle stop screw. This may often cause the engine to "run on", as when the ignition is turned off, the throttle needs to be shut off further than it's idle position. Always set the base idle by the idle solenoid, and ensure that the throttle stop screw is backed off, which allows the throttle linkage to return past idle when the ignition is turned off.

Inlet manifold V8 - Alloy V8 intake manifolds are renowned for corrosion around the four water port faces and the thermostat housing. The manifold faces also warp around the EGR (Exhaust Gas Recirculation) ports because of the hot exhaust gases crossing under the manifold. This can be externally evident by oil pooling in the middle of each side of the manifold below the carby. Manifolds can be rewelded and refaced, but only to a certain limit.