The Isuzu three-litre engine is by no means on its own in this regard, but as a modern turbo-diesel, it can be affected by problems surrounding its Exhaust Gas Recirculation (EGR) system. In line with emissions controls mandated by the governments of the world, an EGR valve allows the Isuzu engine to consume a percentage of its own exhaust gas as a means of cleaning up tailpipe emissions by burning that portion of its exhaust twice.

But the EGR valve is also involved in ensuring that crankcase fumes get burned in the engine and don’t escape into the atmosphere, and that’s where the ducks of doom start to line up. Those exhaust gasses that are given a second trip through the engine contain soot (a normal component of a diesel’s exhaust emissions) and when they combine in the EGR valve with the oily fumes from the crankcase, the oil and soot can quickly turn to a black, sticky gunge that can clog up the EGR valve and coat the inlet manifold, reducing its effective diameter.

Like we said, this is anything but an Isuzu phenomenon, but it’s something that no owner of a modern turbo-diesel can safely ignore. If it’s allowed to go unchecked, the layers of oily soot soon build up and the EGR valve becomes jammed open. At which point the vehicle’s emission-controls aren’t working and it’s – technically - unroadworthy.

The other symptoms can include a check-engine light illuminating on the dashboard as well as poor starting, a loss of power, reduced fuel economy, and rough idling.

solution

The best advice is not to wait until the EGR and intake manifold clogs up. Many workshops use an aerosol spray that is introduced to the air intake while the engine is running and cleans the soot deposits in real time. The recommendation is to have this done at every service, and while the treatment can easily cost $100 a pop, it’s still cheap compared with the alternative.

Which is, of course, to disassemble the EGR valve and the inlet manifold and plumbing and manually clean the grot out of it. This is not a simple job, if only because of the degree of disassembly required to get to the affected bits and pieces. Suddenly, that hundred-buck shot of aerosol is looking pretty cheap.

And even if you do go down the hand-cleaning route, there’s no guarantee that the EGR valve will come back to life. Most experts agree that once the valve has become stuck open, it’ll almost certainly need to be replaced at a cost of anything up to $1500.
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