My friend has a 08 Mini Cooper S 1.6 turbo and her car has been misfiring. Some of her other symptoms are stalling, rough idle, knocking or tapping, hard to start, and poor acceleration. The car has had a rough idle since she’s bought it a month ago. We changed her oil and oil filter soon after. Started having bigger issues after she let her friend go for a joy ride. We replaced the spark plugs, replaced the fuel filter and cleaned the fuel injectors. Also cleaned the maf and map sensors with cleaner. Codes are p0300-304 and oil light on. Autozone says it’s the fuel injectors but they seemed to spray through fine after the cleaning. I’m new to working with minis and would appreciate any thoughts or suggestions.

Update: As it turns out her car had practically no oil in it. I'm assuming there is a leak somewhere but i haven't been able to identify it. I added 2.5 qts and after a rough start with some stalling she turns on fine now and drives like normal. The drain bolt for the oil pan seems clean and I didn't feel any oil around the oil filter. Considering I did an oil change about a month ago and she started having problems roughly a week or two after I'm guessing it's leaking fast.

 

Too late now but having a sample of the old oil analyzed might shed some light on what's going on. 'course, I'm assuming what's going on is some kind of problem with the timing chain and the oil analysis would turn up high levels of metal in the oil.

Also, carefully examining the oil from the filter and even getting a good look at the filter element and what it may have caught in its folds is also a good idea.

I assume you used the right oil and filled the engine correctly?

Is the oil light on solid? A poorly running engine if the idle speed dips too low can have the oil light on as oil pressure drops quite dramatically with the engine running below its nominal idle speed.

You need to confirm the oil pressure is good at hot idle. With modern engines oil serves to not only lubricate the engine but to work systems like valve timing advance/retard and even with some MINIs control the amount of intake valve lift. Proper oil pressure and flow are a must.

Did you observe the fuel injectors spray pattern in an injector cleaning/testing machine? If the spray pattern looks good that's one thing. But injector flow should be good and all flowing very much the same amount.

 

We used 5W-30 full synthetic for her oil change and her last oil looked straight black I don’t think it was changed for a while. I was assuming the oil light on her car was low oil pressure I haven’t actually tested the pressure myself yet. Unfortunately she probably threw the old filter away so I don’t think I have any way to inspect the old oil. The injectors looked very dirty before cleaning them and after the spray looked the same on every one but I’m thinking that since we haven’t ran her car very much after cleaning them that autozones code reader was pointing to the injectors because the codes haven’t updated.

 

It is or should be SOP to once something is done that is expected (or at least hoped) to address the issue is to clear the codes then road test the car. If the CEL comes on then read the codes and go on from there.

But before a road test oil pressure should be checked with a trust worthy gauge. You don't want to be driving around with the engine low on oil pressure.

 

yeah that’s the plan my biggest issue with doing a road test is the misfiring, knocking sound coming from the engine plus the stalling out but hopefully if I can fix the oil pressure issue those things will go away. I appreciate the help I’ll work on the oil pressure first and go from there.

 

Doesn’t sound like the coils were changed with the plugs? If misfiring, I would get a new set of coils. The oil light could be from a slugging engine, too.

 

Mentioned this in my 1st post but it bears repeating and that is a poorly running engine which experiences dips in idle RPMs can trigger a low pressure oil light. And the drop in pressure is real but is not a real sign of a low oil pressure problem but just a side effect of a poorly running engine.

I like to observe oil pressure at hot idle. 'course, if the engine won't idle...

And with some cars the factory service manual had an oil pressure call out at say 5K RPMs and with the oil up to 90C.

But if possible you want to know the oil pressure is up to spec when the engine is running normally (as as close to normal as it can).

 

I’ve read that it could be the coils causing a misfire but we haven’t replaced them yet because the likely hood of all 4 coils being bad to cause all 4 cylinders to misfire just doesn’t seem right. That being said I plan of doing a resistance check today on them. One of our biggest problems right now is money so we’re just trying to narrow it down to what it really is before we start replacing a bunch of things it might be.

 

I picked up an oil pressure tester last night and I’m gonna see what it says just to be sure. Another concern of mine is when I did the oil change I took the oil filter out of the cap and the plastic piece and spring in the bottom came flying out. I tried assembling it best I could by hand but it wouldn’t stay so I screwed it back into the housing and took it out and it seemed like everything was in the right place. Just wondering if you think the filter cap could be faulted because it came undone.