Has anyone experienced a problem like this or have any clues?: When my Mini reaches 1/4 tank the engine starts running rough and the check engine light comes on. When I fill the tank the engine won't start (just that time, but ok after that). Same scenario over and over. Car's been at the dealer for a week and they don't have a clue. The car's not storing any codes and the gas isn't bad.

 

Could be a bad gas cap, fuel filter, tank or pump.

 

the damn thing only has 2K miles on it. Why would a bad gas cap cause a problem like this? It did display a gas cap loose code at one point, but I repeatedly checked it and it was on.

 

Sounds like you are running out of fuel. Possible causes:
1. As mentioned, could be blinded fuel filter
2. Fuel pickup tube no longer down in bottom of tank.
3. Fuel level sensor reading 1/4 full when actually empty
4. Fuel pump going bad.

 

That's why they invented warranties.


For some reason, the tank has to be under vacuum for the system to work right. Both Gen1 and Gen2 cars are this way.

 

As lhoboy said the tank is under vacuum.

If there is a crack or gap in the gasket, or cap itself, or a loose connection between the filler tube and the tank, Bad gasket at the fuel pump on the tank etc. All of these can cause a small vacuum leak and the car will not like it.

 

It's the HPFP, I'd bet a paycheck on it.

 

with 2 bars on the gas gauge my car will slightly pop/missfire at 5500/6000 rpm in first gear.

 

Hmmm.. Calling the dealer today to talk about the HPFP. Sounds logical to me. Have to admit, had to Google that one. Seems BMWs, AKA Minis, are notorius for failing early. Sorry, can't bet a paycheck on it. I'm going to need the cash for the extended warranty that I'll be purchasing the very next time my feet hit that dealership. This adventure would have cost a fortune!!

 

thanks to everyone for their suggestions. The dealer is telling me that the "purge valve" was stuck open. Not sure exactly what that means, but... Picking it up tomorrow. We'll see....

 

You should have taken Kevin's bet, but I guess that would depend on the size of his paycheck.

 

Kevin is presently unemployed.

Glad that the problem is <apparently> resolved, especially if it wasn't another HPFP. We all need to start hoping these things start working better - especially in new cars like the OP's. Hopefully that pump has been improved semi-recently.

 

My 2010 Cooper just had this problem - I let the fuel get down to 2 bars on the indicator and filled up at Chevron using 87 octane - the car wouldn't start - it just kept cranking - called roadside assistance and before they got there the car would start after having waited about 15 minutes - the car is at the dealer now and they initially suspect either bad gas or that I should not have used 87 octane

 

Your car will run on any octane, that's dealer b.s.

However, since MINI recommends a minimum 91+ octane, and the engine works best with 91+ octane, why are you using 87?

For another dollar or two per fill-up, you should use premium.

 

87 is cheapest and I'm frugal

 

87 octane versus 91 octane gives you decreased engine performance and decreased mpg.

If you drive about 15,000 miles a year you'll use about 500 gallons of gas. I usually pay about 20 cents a gallon more for premium versus regular. That comes out to about $100 a year, before considering the decreased mpg you'll get from regular gas.