The autoignition of gaseous mixtures representative of coal derived low-heating value fuels in a direct-injected diesel engine was theoretically investigated over a pressure and temperature ranges of 10 to 50 atm and 800 to 1000 K respectively- A computer model was validated with experimental data from an engine operated on direct injected synthetic coal gas. The computed results demonstrated the importance of the characteristic time associated with the chemical kinetics when compared to the fluid mixing. High gas temperatures resulting from high compression ratios, high boost, high inlet air temperatures or other ignition aids are needed to ignite these gases in a compression-ignition engine in a timely manner. The predicted sensitivity of the autoignition delay time to changes in the engine operating conditions was significant for temperature but almost negligible for pressures up to and slightly in excess of 30 atm