Original sentence: Based on an early computer system, most Lean Burn Computers were an open-loop emissions control system with no provided diagnostic port or "Check Engine" warning light, were difficult to troubleshoot, and were greatly responsible for the poor reliablity reputation which dogged Chrysler at the time.It also provided drive for the ignition coil directly, eliminating the separate ignition module.Many Lean Burn Computers were replaced with the more reliable electronic ignition module and centrifugal/vacuum advance distributors used on earlier Chrysler vehicles, almost universally to improvements in fuel economy and driveability.Mounted on the air filter housing of most rear wheel drive cars Chrysler produced during this time, it was responsible for adjusting spark timing based on manifold vacuum, engine speed, engine temperature and incoming air temperature; by doing this, Chrysler eliminated the traditional vacuum and centrifugal timing advance mechanisms used on distributors in order to provide more accurate spark timing
Edited sentence: Based on an extremely primitive computer system, most Lean Burn Computers were an open-loop emissions control system with absolutely no provided diagnostic port or "Check Engine" warning light, and were notoriously difficult to troubleshoot and were greatly responsible for the poor reliablity reputation which dogged Chrysler at the time.Mounted on the air filter housing of most rear wheel drive cars Chrysler produced during this time, it was responsible for adjusting spark timing based on manifold vacuum, engine speed, engine temperature and incoming air temperature; by doing this, they completely eliminated the traditional vacuum and centrifugal timing advance mechanisms used on distributors, hopefully providing more accurate spark timing.On a happier note, most Lean Burn Computers were unceremoniously torn from their cars and replaced with the far more reliable electronic ignition module and centrifugal/vacuum advance distributors used on earlier Chrysler vehicles, almost universally to improvements in fuel economy and driveability.They also provided drive for the ignition coil directly, eliminating the separate ignition module