Mitsubishi S4S Engine Black Smoke Under Load
Fault Codes & Symptoms
Black smoke under load Related symptoms: - Low power under load - Slightly higher engine operating temperature - Audible hissing sound from engine bay under load The forklift runs fine with no load, but as soon as we lift something heavy, it billows black smoke from the exhaust.
Confirmed cause: A loose clamp on the charge air pipe between the turbocharger compressor outlet and the intake manifold, causing a significant boost leak under load. Repair performed: Replaced the faulty clamp and the slightly swollen charge air hose. Cleaned the oil residue from the connection points. Verification: Operated the machine by lifting several heavy loads to full height and accelerating repeatedly. No excessive black smoke was observed. Technician notes: - This is a classic example of a boost leak. The smoke only appears when the turbo is supposed to be making significant pressure. - Always check the simple things first. A visual inspection of all intake piping can save a lot of time. - Oil residue around charge air pipe connections is a tell-tale sign of a leak.