2004 Mini Cooper Base (R50)
Codes:
P0128 (Coolant temp low), P0300 (Random cylinder misfire), P0313 (low fuel misfire)

Symptoms:
On partial throttle (just enough to keep it at speed) over 3K RPM (in any gear) the Service Engine light flashes and the car goes into limp mode until it is turned off and back on again. It performs just fine on WOT runs all the way to red line, and does fine if giving it moderate gas or on release in the 3K+ range.
It will only go into limp mode if keeping a steady throttle at 3k+ rpm for anything more than 4-5 seconds.

Work already done:
Plugs, wires, coil are all new and the contacts are still clean looking.
Compression is good.
Replaced fuel filter and cleaned out the housing.

Before I go replacing the entire fuel pump, is there anything else I could be looking at?

Thanks in advance

 

PO3XX could be a dead knock sensor? They do fail. The big headache with those is it has to go into service mode to get to it if I remember correctly.

 

Thanks for the suggestion - any good way to test the knock sensor?
Can I test run with it disconnected, or will that cause more problems?

 

Got no clue to how to test or disconnect it. It's on the engine block well hidden. The flat rate book shows this as a 5 hour job for a $25 to $30 part.


PS: I was given a good talking to by the shop guy about using ONLY top tier fuels by the way, which sometimes I hadn't. That was 4 years and 40K miles ago and no problems since by being careful about where I shop at gasoline stores.

 

Coolant temp sensor might be a suspect. A failing one will tell the ECU wrong signals for your AFR. It can cause hard starts & misfires. The cheap part is beside the thermostat. You've to remove the ECU to get to it w/ a deep socket.

 

Thanks for the responses, guys - I'll be taking a look at the knock sensor and the coolant temperature sensor.

Good insight on the temperature sensor, I didn't realize that it could affect AFRs.

 

Welp, after replacing the coolant temperature sensor and the thermostat, there was no improvement. I was trying to take a quick peek at the knock sensor, to make sure it was plugged in, but I cannot find where the plug end is. I know the sensor itself is under the intake manifold, and that the wire should lead to the right, under the fuel rail, but where does the actual plug location sit?

Thanks!

 

Replaced the fuel pump. While a definite improvement, it has not solved the original problem of dropping into limp mode at 3k rpm.

Any other ideas of what I can check?

 

Hi!
Did You Check The Fuel Filter?

 

Yes, I did give it a check. It was replaced recently, and I only had new gaskets on hand, so the old (new) filter is back in there for now.

Agh

 

Well, a few of the most frustrating months later, and the problem was solved with a new serpentine belt.
The old belt was looking cracked and ripped, so after replacing it (with a smaller size 6pk1030 that was the closest I could get to the stock 1033, but the shop got it on, just fine).

No more limp mode. Car runs like a champ.