Got an R56 1.6 Cooper with an N12B16A engine on a 56 plate with 149K miles. Been a good little runner these past few years. Now developed a weird problem. My recent test drive explains the problem exactly.
Got in and started her from cold. Warmed her up, cleared the calculated mpg value and headed out onto the road. Motorway, M1 Southbound JN10 to 6. Doubled back at 6 and headed back up to JN10. Car is driving beautifully. I'm not driving her hard, but also just cruising at 70m.p.h.
Head home and pull up on the drive. Calculated m.p.g. for this run is 44. Not bad for an old girl. Check the short term and long term fuel trim. Short term is oscillating between 0 and -0.78. Long term is -0.78. As far as I know these values are quite acceptable.
Then stop the car. Take the key out. Wait for 2 minutes. Key in. Start. Running like a tractor. Engine warning light for misfires on Cylinder 2 and 3. Turn off and on a few times. Same result. A warm start and she runs like a sack of manure with misfires.
Sparking plugs are not that old. Valve cover is new. Just changed the MAP sensor. Just fitted a new CAT. Timing chain only done about 20K. No discernible air leaks.
How does a car go from running that sweetly to running like a dog just by turning it off and on again?
I am stumped.
Got in and started her from cold. Warmed her up, cleared the calculated mpg value and headed out onto the road. Motorway, M1 Southbound JN10 to 6. Doubled back at 6 and headed back up to JN10. Car is driving beautifully. I'm not driving her hard, but also just cruising at 70m.p.h.
Head home and pull up on the drive. Calculated m.p.g. for this run is 44. Not bad for an old girl. Check the short term and long term fuel trim. Short term is oscillating between 0 and -0.78. Long term is -0.78. As far as I know these values are quite acceptable.
Then stop the car. Take the key out. Wait for 2 minutes. Key in. Start. Running like a tractor. Engine warning light for misfires on Cylinder 2 and 3. Turn off and on a few times. Same result. A warm start and she runs like a sack of manure with misfires.
Sparking plugs are not that old. Valve cover is new. Just changed the MAP sensor. Just fitted a new CAT. Timing chain only done about 20K. No discernible air leaks.
How does a car go from running that sweetly to running like a dog just by turning it off and on again?
I am stumped.
