I have a base 2008 Mini, auto trans, R56, N12. I'd had an idle hunting problem before, and after replacing the MAF and throttle assy., did a smoke test and saw a leak from the valve cover (driver side rear). So I replaced the valve cover & gasket, and fixed the issue.

I've also had a P0442, minor evap. which appeared to have been from around the fuel filter cover, which I believe I've resolved.

Just recently, I've had a really bad idle issue; hunting from 700 to 1500 & back down to 500 and stall; that sort of behavior. I've seen a number of error codes, like P115C, P2177, and some misfire codes. And when it's misbehaving, and I run my Torque app. the AF Ratio is very lean; say 26 or so. The car runs fine when it's off idle; to go anywhere around town, I just have to shift to neutral at stop lights and keep the engine above 1500 or so, to keep it from stalling.

But the really interesting thing for me is that if I disconnect the battery, and wait a bit to Reset the ECU, it gets better. Just now after a reset, it idled fine in my garage for about 10 minutes, with the AF ratio steady at about 14.3, which I'd say is perfect. So it's not just time passing with the engine running after a ECU reset that makes things go wrong, it appears to be actual driving. I understand that the ECU may do something along the lines of learning your driving habits; it appears, however, to be badly misunderstanding what I am trying to teach it. If anyone has any idea as to what might be the cause of this inappropriate re-learning, or has experienced this sort of thing, I'd appreciate hearing about it.

Mark

 

could be that you have a loose connection somewhere...go over the pipes and sort of wiggle them.

the re-learn isnt the issue...i did so many relearns and reset adaptations for both engine and transmission. you wont feel anything of that sort.

 

AF ratio of 26 is scary lean. Sounds like a fuel delivery problem to me. Check HPFP pressure, etc., should be able to read that with Torque.

 

This is a Base Mini; not turbocharged, not supercharged, normally aspirated. So I am pretty sure it lacks a HPFP. And I am also pretty sure, therefore there is no fuel pressure sensor I can read with Torque. I did buy a injection fuel pressure kit/gauge, with a mechanical gauge, which should just attach to the fuel rail. Unfortunately, the pin on the adapter hose for the schrader valve did not have enough reach to open the schrader valve on the fuel rail so I didn't get a reading. I guess I'll buy the tool to remove the valve core from the fuel rail; that should give me a reading.

Still, I wonder why the AF readings are just fine after a ECU reset. I believe there is no way an ECU reset could affect the pressure that an the in-tank pump will deliver. I could sort of believe that some newer direct injection systems might have the ECU control the fuel pressure electronically to get better fuel economy and/or lower emissions, say with an electronically controlled pressure regulator; but I think that's unlikely in older, non-direct injection systems like my base mini---maybe I'm wrong there.

 

I have been able to get readings on the mechanical gauge by backing out the valve core on the fuel rail schrader valve a bit. Both in the case after a ECU reset where it's idling OK, and the case after driving where it hunts up and down, and stalls, its' reading a bit over 50 psi, which I think is just fine. So I think the in-tank pump and regulator are fine.

 

Sorry it was late and I didn't read carefully. I still think it is a fuel delivery problem. Bentley manual says for N12 you should be getting 72.5psi, if you are only measuring 50 that might be your problem. Could be the fuel pump, regulator, or clogged fuel filter.

Other possibilities:
1) air mass sensor messed up so ECU thinks there's less air than what is really flowing, so it limits the injector duty cycle
2) injectors are clogged up.
3) some other sensor is messed up

 

OK I re-read the OP and you are getting some codes:

P115C: Mass Air Volume Flow 'A' Too Low
P2177: Fuel Trim Limit Exceeded System Too Lean

If you don't have a Bentley manual you should get one.

Check your MAF and fuel pump/regulator/filter.

 

I do have a Bentley Manual. On p. 160-11, I see system pressure (non-turbo) 50.7 psi. I think you are looking at the turbo line, when you see the 72.5.

 

Hmmm, I have the edition that covers up to 2013, on page 160-9 and 160-10 the only spec for the low pressure pump from the tank is 72.5.

P2177: Fuel Trim Limit Exceeded System Too Lean says your ECU knows it is running too lean and is trying to increase the amount of fuel. The way it adjusts this is by increasing the injector duty cycle. So there's either not enough pressure at the input to the injectors or the injectors are clogged or otherwise faulty. You could try removing them and having them tested but probably easiest to just replace.

Edit: I looked up the injectors, they are expensive so it doesn't make sense to throw $ at the problem without checking the other stuff first. Start by checking the fuel pump and filter. You didn't say how many miles, but the car is going on 10 years old and it's not unreasonable to suspect that the filter might be clogged up or the pump going bad. Once you have confidence in not just the pressure but also the flow capability of the pump and filter then have the injectors tested.

If you clear the P115C does it come back?

 

The thing that mystifies me is why it will sit there and idle just fine after I reset the ECU. If the injectors were clogged, or the fuel filter was clogged, or the pump was weak, or there was any other real physical problem, that problem would still be there after an ECU reset. So I'm inclined to think about mental issues, which unfortunately is leading me down the path to replacing the DME/ECU. BTW: when I first got the car, I did run a bottle of Techron, to clean the injectors.

 

My AFR is off the chart (dyno) at idle. It only approaches 11 - 13 above 2 - 3K RPM, but then again, it's a hi-perf MCS. Your problem descriptions sound like air leaks / AFR issues --- bad hose connection, throttle body binding, etc.

It takes awhile for the ECU to recognize a small leak or slight blockage. A major problem will be seen immediately and codes set. I've seen very few, if any, ECU failures documented.

I asked about your previous repairs because some of us DIY'rs get careless with workmanship and create our own problems --- myself included! Your current problems seem related to work you've already done, and possibly haven't completely fixed yet. Do you have a repair history from the previous owners --- walnut blasting, etc?

 

I replaced the valve cover and gasket on 12/7/16. I first got the P0442 on 2/21/17, and had the smoke test done for the minor evap on 3/7. I had decided to live with the 442 for a while, since it was minor. On 8/1 I first noted the bad hunting at idle, and on 8/12 took it into a local shop, who could not diagnose the problem (and who charged me nothing, which I thought was nice). On 8/13, I decided to look at the leak out the fuel filter housing, because, who knows, even though it was coming up a a MINOR evap., maybe the Mini was thinking it was a bigger deal, than I did. I found, sort of as you are suggesting, that probably I caused the minor evap. when I changed the fuel filter; apparently I had put in the black, Diesel only gasket, instead of the orange (OK for petrol?) gasket; plus this time I used a bit of o-ring grease on the gasket. I have not had the 442 return since changing that gasket, and re-seating the lid on the fuel filter canister. After resetting the ECU, the problem returns after about .6 mi. of driving; but not if I just idle in place.

Interesting about the lack of documented ECU failures.

 

I agree with OBW, assuming no tampering or other physical abuse of the ECU, I think it is the least likely thing to be a problem.

You've replaced the fuel filter and MAF already so that's not it.

When the car is sitting at idle, fuel consumption obviously is very low so if the pump was starting to fail then it could be able to maintain pressure at idle, but as engine load increases fuel demand goes up and the pump may not be able to keep up.

 

With an idling AFR of 14, and a driving(?) AFR of 26, and "RPM hunting", it sounds to me like too much air in the system. I prefer excess air over insufficient fuel because you're (meaning anybody, not you specifically) more likely to damage the air hoses / connections than have a fuel-supply part failure.

Then too, if the current "hunting" is similar to last years "hunting", it's quite possible one of the new parts failed. If either the MAF or throttle assembly failed, and you bought them from a Mini dealer, they are guaranteed for at least one year --- even if you did the labor yourself. Sounds like your earlier efforts were mostly successful.

 

It seemed to me that it was the ECU. So, I found a vendor that diagnoses and repairs ECUs; seems to specialize in BMW, and does handle Mini. So I sent them the ECU. He's reported back that the main processor was shorted, and so the ECU/DME is not repairable because the processor is integrated into, not soldered onto, the PCB. So, apparently this is now a documented case of the ECU going bad (depends on how paranoid one is, I guess). Anyhow, I have decided to have them procure, and rebuild a rebuildable ECU, and have it reprogrammed to match my vehicle's VIN, to avoid problems with the CAS and BC1/U not matching the DME. Not cheap, but cheaper than a dealing with a dealer (which there are none of in this town anyway), and less hassle than buying a 4 or 5 matching module set from ebay, and then not having the electronic VIN match what is on record with the DMV, and the physical VIN tags on the car.

I will let you know in 9-14 days what the results are; unless my FL vendor gets flooded with Irma. Wish me luck. But as I always say, "What could possibly go wrong?"

 

I got the replacement remanufactured ECU back from the vendor. After install, the car started up, locked/unlocked, & showed the correct mileage; so the programming to match my VIN and odometer reading was done correctly. The biggest problem I had right before sending off the ECU (large cloud of white smoke on accelerating from stop) was resolved with the ECU. However there is still a bit of idle hunting and an occasional stall at idle. Since the car was running so poorly right at the end, I thought there was some possibility of fouling; so I'm running a bottle of Techron through; I think the remaining problems are gradually getting better. I know, the AF at idle is more like 16 now, rather than the 26 I'd seen earlier; still a bit lean, but better.