4JA1 - very reliable, easy to maintain, matibay, and fuel frugal diesel engine. Had one with my 92 Isuzu LS Pick-up with 281,000+ kilometers in it. Tamang maintenance lang talaga ang sikreto. Common lang talaga dito yung medyo mausok. Sa akin ganon din compared sa iba naming sasakyan (Intercooler Turbo 4D56, TDCi, and Hyundai CRDi) pero hindi naman mausok na akala mo nagpapaapoy ka ng mga dahon at sobrang itim. Normal na usok lang from exhaust and the smell is like normal although yes compare sa ibang engine namin medyo (iba ang amoy, but still amoy diesel pa din). Almost 70% of the parts in my pick-up are still the original parts when it was bought brand new way back in the 90s. Only problem experiencing right now is this:

1. It is somewhat shakey (maalog) especially pag naka-ON ang A/C. Sa lower idle speed nya the car starts to vibrate abot sa cabin and yes noon malakas. At first I thought engine supports, but then we had it fixed with the help of our mechanic na may ganon din na sasakyan, nilinis lang pala yung Air Filter kasi madumi na even konting lumot meron na plus nilinis din also yung Fuel Pump because may tubig na daw i don't know gaano kadami. It went back to normal again, hindi na maalog sa kahit anong idle speed range and we were able to bring down the idle speed to normal which is 850 rpm. The only thing is it's starting to rattle now again pero very very minimal lang and very very weak na rattle lang pero syempre lahat naman tayo metikuloso sa sasakyan natin diba? i'll have it checked nalang again (the fuel pump) and I will try to clean the air filter again this time and maybe change it next week. We'll see the difference kung andoon talaga. But then if hindi pa din mawala ang rattle/vibration sa paglilinis ng air filter and fuel pump, maybe I really have to check the engine supports.

Over-all this 4JA1 engine is a very reliable diesel engine. Kahit yung maikarga mo dito na fuel (by accident) ay madumi or may water or whatsoever (hindi naman maiwasan ito sa ibang gasoline stations esp sa far-flung areas), never mo ma-eexperience na masisiraan ka ng engine. Base on my experience, pupugak lang ng konti but when nasunog na yung fuel, okay na sya. Unlike some of my friend's CRDi engines, nadumihan yung fuel. Boom! Sira na injectors