So I've been having this issue with my '08 MCS JWC for a few weeks now where the engine randomly "hiccups"- it misfires for half a second or so then resumes normal operation. When this first surfaced, it resulted in the yellow engine symbol (reduced power warning, not the MIL), although I didn't notice any reduced power other than the momentary hiccup. No OBD codes. Took it to the mechanic, and per Murphy's law the symbol went away and it wouldn't act up for them.

I've had it back for a week or so now and it just hiccuped again, this time it did trip the check engine light/MIL, fault codes P0300 (random misfire) and codes for all 4 cylinders (P0301, P0302, P0303, P0304). It seems the engine completely dies for a split second and comes back.

Any ideas? Seems to me like a possible crankshaft sensor on the fritz?

 

Two things come to mind:

1.) Have you walnut blasted the valves? They could be caked with carbon.

2.) High pressure fuel pump. I believe the warranty was extended for this part.

 

1) No I haven't. All mechanics I've talked to are only interested in the seafoam treatment (and you don't have to look far on this forum to see it doesn't work), and I don't really have a garage at my disposal to take the intake manifold off and scrub. Any further pointers that the misfire is in fact carbon build up?

2) How do you know if it's the HPFP? I just read >1000 psi fuel rail pressure with my scan tool. Based on that, seems like it's working...

 

My first guess is carbon build up. I would check that first. While I know some on here think seafoam will clean your valves as far as im concerned it wont do much once you have a hard build up. Plus direct injected type engines make it even less likely to do anything. Your best bet is walnut blasting. How many miles do you have on this MINI?

 

Currently at 95k. Bought it used at 74k from Carmax.

 

The best way to tell if they are caked is to pull the intake and look.

There are independent shops out there that will do walnut blasting for ~$300.

 

You can do what cerenkov said. But with that mileage im sure your due. Dont waste your time with any fancy chemical to clean them. Do the walnut blasting and save yourself the headache.

 

It could be carbon deposits, but there are a lot of other things that can cause this as well.

How long since the plugs were changed? Pull them out and have a look, and if in doubt change them.

What fuel are you using? If you are using a low octane fuel, or have a bad batch of fuel this can cause this problem. Try filling up with the best quality highest octane fuel you can find and see what happens.

 

I also purchased my 07 MCS at CarMax at 45k and 2k later I had the valves walnut blasted because I was having similar trouble that you are describing, I didn't know any better so I took it to the dealer and it cost me $800 and they flashed the ECU firmware to the most recent version. Later I found out other places were only charging $350-$550, the latter at another dealer. My valves weren't as bad as most N14's but it still brought back some power that I felt was night and day! Seafoam is useless, I have seen other members pictures of their valves when they took theirs in for walnut blasting and couldn't believe how bad it was even after all of that seafoam.

Believe me your valves have got to look pretty bad at your mileage if they have never been clean before! Anywhere you go they will first suggest getting the valves walnut blasted and then go from there, you might buy a few bottles BG 44K as this will clean you combustion chambers. You can find them on eBay for cheap, all of the professional shops use this product as it is for professional only. All you do is pour the can into your gas tank, I have gone through 5 bottles and after 3 bottles I peaked down into the cylinders and instead of seeing blackness I saw a silverish color on the tops of the pistons. When the black carbon gets hot it cause the fuel to ignite too soon causing pinging, knocking or whatever you want to call it.

 

+1 on changing the plugs, if they are OE plugs they past the point of junk.

Given the miles on the car, add changing the fuel filter to the list of usual suspects as well

With a problem like this, it is very likely that it may have multiple causes, not just a single one. So bad coil pack(s) and worn plugs are one possible combo.

Crank sensor is another one since all cylinders are dying, that sounds like the DME is having to re-synch.

E30 BMWs would exhibit the same symptoms as your car once the plugs wore to certain point. The DME indexed off one plug wire via an inductive pickup. When that plug failed to fire the DME would kill the engine until it was sure it had clean signals again. It was a baffling problem to diagnose.

 

Reviving an old topic here I see. I wondering if the OP ever found a perfect solution for the P0300 thru P0304? I had a CEL at lunch time with these 5 all together. Seemingly, I've done about all the standard fixes but I may be missing one or two? Changed plugs, replaced pipes, changed fuel filter, coil packs just recently, and HPFP in the last few months. Mine only seems to occur upon cold start, if the car sits for 4 or more hours. Ambient temperature might make a difference. Started fine in my home garage with a little stumbling. At lunch in the colder parking garage at work, stumbling was worse and it popped the CEL almost immediately. I may have been pending. I've not (yet) seen those codes with the engine warm.

 

Check in tank FP.