I am in the process of restoring a 1996 Mini Cooper 35, and I cannot seem to fix the poor acceleration issues. So far I have replaced the lambda sensor, the ignition coil, the leads, the plug and the vacuum pipes, yet nothing seems to correct the reluctance felt in the acceleration. A mechanic has run the test codes and nothing is showing. Any suggestions? Rod DeLaet We would strongly advise a compression and leak-down test. The one thing that completely gets overlooked on later injection-equipped cars is that the engine may be worn and so producing excessive emissions from the crankcase. These emissions are re-circulated by the breather system connected to the plenum unit, and so are drawn back in to the engine. The ECU continually assesses the ‘health’ of the engine and makes adjustments to fuelling, ignition, idle speed and so on. But if severely worn bores, piston rings and so mean the emissions being produced exceed the level of selfadjustment programmed into the ECU, the engine will generally run pretty poorly and be flat on acceleration. A simple check on this is to run the crankcase breather pipes into a catch tank of some sort, temporarily block off the ports on the plenum and see how that makes the engine run.
Check your compression.