I posted previously regarding a loss of power under hot conditions. One by one, I replaced each of the intake sensors - MAF, MAP, & Temp with no change in the problem. No error codes ever occurred and problem would correct itself within a few miles, presumably after under hood temps dropped back down. I recently had an even more severe loss of power pulling onto I-4 after stopping for lunch and leaving the engine idling while I ate in the car. This time it posted an error code but I don't remember the code at the moment but a possible cause was listed as low fuel rail pressure. I'm aware a number of Mini owners have had HP fuel pump issues with loss of power among them so I decided to replace mine with a new, not rebuilt pump. Sadly, the loss of power after idling under hot conditions is still there but not as severe so I'm thinking the pump was only part of the problem.

So my question is, which sensor is most likely to contribute to a loss of power when it gets too hot?

 

Anything over 140F intake air temps the car will pull timing which will reduce the power. So if you go from idling for 30min to getting on it, the car is going to reduce power until the intake temps come down.

 

Thanks for the reply. I can monitor the intake air temp and it doesn't get that high, low 90s mostly when this occurs but I suspect the underhood temp is in the range you're talking about so what is failing. I've already swapped out the MAP/Temp sensor with no success.

 

How are you watching the intake temps, on your phone with a obd adapter or on the cluster?
Could look at the fuel rail pressure sensor and watch the fuel pressure after sitting.

 

Watching with OBD and dash command. Have also tried monitoring FRP but the difficulty is that's such a dynamic measurement and trying to compare one instance to another during acceleration is impossible. I have noted the pressure at various steady speeds when power is normal but haven't had the opportunity to do the same when the power is down. As for noting the value at idle, I've never noticed any difference and I would also expect the idle characteristics to change so the problem seems to only affect acceleration.

The comment about timing being rolled back makes a lot of sense to me because no faults get posted when this happens so the assumption is no values have exceeded expected ranges. And I have little doubt that all the sensors are working together to establish operating parameters such as timing, mixture, boost etc so it's hard to pinpoint which sensor may be reporting erroneous readings. I can watch the timing as well but again, it's a dynamic value during acceleration so establishing a baseline is extremely difficult but I've not tried before. That may be easier than fuel rail pressures. Speaking of, do you have any idea what max pressure should be? That would be a value I could compare between running normally under hard acceleration and when the power is down. I believe I've seen it approach 1500psi under normal conditions.

 

They say fuel pressure should be 1700 under full throttle. And 750 at idle. https://new.minimania.com/Mini_Coope...lication_Guide
You can datalog on dash command so you can start a log with boost, rpm, fuel rail pressure, timing, and intake temps and see if there is a difference in anything between it sitting for 30 mins then getting on it and just getting on it after normal driving.

 

Thanks for the link and yes, I'm aware of the datalogging ability but haven't pursued it yet due to uncertainty of which parameters to examine. I'll try it now.

 

Just to close out this thread - I have thrown in the towel and traded the car in. BTW, the code posted when the power loss is greatest is P1497 which unfortunately doesn't really define a source for the problem. I wish I could have offered some helpful information for other owners but I'm done with it.