POOR AC­CEL­ER­A­TION

Mini Magazine - - Tech -

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.

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