Alfa Romeo JTD / JTDm

Fiat's larger common-rail diesels as fitted to Alfa Romeo — the 1.9 and 2.0 JTDm of the 147, 159 and Giulietta. The JTD family matters historically because Fiat's group developed and productionised common-rail injection, and the technology was then licensed widely; almost every modern diesel in this catalogue descends from that work.

The recurring items are those of the era: swirl-flap mechanisms in the intake manifold, whose linkage fails and whose debris can reach a cylinder; EGR blockage; and the diesel particulate filter on later versions, with short-journey use behind most regeneration failures.

The 1.9 in particular is known for injector wear producing a rough cold idle and a rattle, and — as on the Fiat 1.3 and the PSA DV6 — turbocharger failures that trace back to a carboned oil feed rather than to the turbocharger itself. Fitting a replacement without clearing the supply repeats the failure.