R52 :: Cabrio Talk (2005-2008) Cooper and Cooper S convertible (R52) discussion.

Sudden power loss and service engine light

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Old 05-07-2019, 03:48 PM
computerdoc
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Sudden power loss and service engine light

2008 Sidewalk convertible with about 45k miles. Started it again an hour after a normal drive and it suddenly lost power, as though the supercharger were operating in reverse. By this I mean if I put my foot it in, it would immediately lose power and slow down. If I lightly accelerated, I could get up to about 25. Service Engine Soon light came on. Limped to a parking lot and shut it off. Opened the hood, found nothing amiss, closed and restarted the engine. Ran normally but light stayed on. Any thoughts?
 
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Old 05-07-2019, 05:46 PM
RockC
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Originally Posted by computerdoc View Post
2008 Sidewalk convertible with about 45k miles. Started it again an hour after a normal drive and it suddenly lost power, as though the supercharger were operating in reverse. By this I mean if I put my foot it in, it would immediately lose power and slow down. If I lightly accelerated, I could get up to about 25. Service Engine Soon light came on. Limped to a parking lot and shut it off. Opened the hood, found nothing amiss, closed and restarted the engine. Ran normally but light stayed on. Any thoughts?
Could be a failing fuel pump or a failing MAF or whatever sensor or sensors the engine controller uses to determine how much fuel to provide the engine. If there is a supercharger pressure relief valve under engine controller control this could be acting up. That the engine recovered after an engine off followed by a restart suggests the problem is electrical in nature not mechanical. (I had another car manifest signs of a problem with the solenoid that controlled the intake cam timing on one cylinder bank. Turned the engine off then back on and the solenoid was operating ok. Drove the car home 30 miles with no problems. But next day in just an mile or two drive to the dealer the engine started acting up again.)

Could start I guess by checking to see if there any pending or permanent error codes logged.
 
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Old 05-08-2019, 07:06 AM
BRGPA
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I had an SES light last week and went to Advance Auto and got them to use their code reader to pull the code. It reset then and hasn't returned- yet. I think you have a more serious problem than I do, but you could go there or Autozone to at least get some idea about the issue.
 
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Old 05-08-2019, 12:17 PM
computerdoc
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Ran fine today. “Service engine soon” light on, but went off after shutdown and restart two hours later. Code check by Autozone showed P1125 only.
 
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Old 05-14-2019, 07:53 AM
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ItsmeWayne
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Often, when the crank pulley fails, the engine will drop into creep mode. If you have smelled burning rubber at any time lately, this will be the problem, for sure. All of these stock crank pulleys will fail, at some point.
The supercharger blow off valve can give the same response, if it failed or the vacuum hose fell off.
There also may be other issues.
 

Last edited by ItsmeWayne; 05-15-2019 at 07:35 PM. Reason: spelling as usual!
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Old 05-15-2019, 04:17 PM
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Old 05-15-2019, 08:14 PM
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+1 on the crank pulley. Look at it while it’s idling. If you see even a slight wobble of the pulley it’s bad. Reach down with a crew driver and see if you can move the outer ring away from the engine.
 
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