Multiple misfires on cold start
 

Hi, all.
2010 Mini Cooper JCW with ~90,000 miles on it. I'm having misfires on all cylinders (P0300, P0301, P0302, P0303, P0304) on cold starts, typically only when the temp is under 40°F or so. Occasionally it's bad enough to put the car into a "limp mode," but it usually stops missing within a minute or so. Once the car starts driving normally, there are no issues, no power loss, full RPM range, everything is fine.

The problem is I had these exact same issues around a year ago, with the addition of P0087; fuel pressure too low. I replaced the hpfp and fuel filter and everything seemed fine until now. After replacing the pump, I did have a fault code P0088, fuel pressure too high, but everything was running normally, I thought maybe the pump had to "settle in" or something, and it only came by occasionally, so I ignored it. The P0088 code is on now.

Is it possible the fuel pump has failed again, twice in a year? Or is this a symptom of some larger issue? The only other thing I can think of is that I'm not sure if the intake valves have been cleaned, I bought the car at 84,000 miles, and I've never had it done. I always use 93 octane fuel, but I've never run any fuel system cleaner or anything through. The pump I bought was OEM, branded "MINI-GULAR," but the original ebay post link now directs to an aftermarket pump for a similar price.

I went ahead and cleaned the valves since I had some time, I figured it needed to be done anyway. I used a boroscope to check cleanliness, so I only got a "before" photo, sorry about potato quality:

https://cimg3.ibsrv.net/gimg/www.nor...bb9d33b607.jpg

This is after almost 90k miles. They looked pretty good after I finished with them, not perfect, but definitely as clean as they deserve to be. There's definitely a difference in feel, mostly in the responsiveness of the throttle, I'll update about fuel efficiency. Cleaned the intake and throttle body while I was at it. Unfortunately, it didn't really help my cold-start issue, so I have a HPFP on the way. Went with a cheaper off-brand this time, as the OEM quality didn't really seem to do anything for me.

sawicki: what kind of scan tool would I need to see what amount of fuel is being requested/delivered?

What condition is your timing chain? Any rattles on start? That mileage is a dead ringer for timing (autocom Pro Plus will do good diagnostics) and will show if timing is retarded (loose chain).

No issues with the timing chain as far as I can tell. No death rattle either, just the misses. I don't know much about it, but I'm guessing the timing chain tensioner wouldn't suddenly start working fine after the engine heats up, right? Once it's running smoothly (a minute or so) there's no problems; no noises, no misfires, no loss of power.

Don't know for sure about the impact to a cold start, but do know that the tensioner relies on oil supply. So if oil is cold (or low) I would think it could impact things like a cold start. If you're close to needing a change, it might be worth it to accelerate it. And pulling, inspecting and cleaning the VANOS solenoid, TC tensioner and check valve are relatively simple once you're dealing with the intake (oops too late!) and might be worth the effort. I could see any of them being sensitive to oil supply and therefore potentially affected by the temp coming up after you start it.

Surprised the valve cleaning didn't make more of an impact--your before picture wasn't great. Seen a lot worse but seen a lot better too!

Daughters Mini,
She was having troubles with it stalling when cold. Hooked up my scanner that can read fuel rail pressure. Notice the pressure was bounce between 700 and 1100. Didnt think anything about it? First Mini!
Then one day it just went bat **** crazy. Every cylinder miss fire and code pointing to hpfp. When I changed the hpfp I noticed the supply line was very soft. Changed the hose. Everything is ok.
Left me wondering if the hose was so soft that it was collapsing under vacuum. It was that soft.

Give you rubber feed hose a good going over!

That makes a lot of sense. I know the oil's not low, but it is due for a change, it's been about 4500 miles or so, I'll go ahead and get that done now. Do you think it might affect it if I switched to a lower viscosity oil for the cold months? I currently use a synthetic 5w-30.

Interesting! I'll definitely be checking that hose out, I didn't pay it much mind when I replaced the pump last time. Well, besides getting angry with it because I couldn't get the god forsaken clip off. Thanks for the advice.

Signs are definitely pointing towards another bad HPFP, I cleared the CEL fault codes after cleaning the intake, and it just came on again; this time a P3091 - low pressure at the fuel rail. Still waiting on that new pump to show up.
As an aside: does anyone know what actually starts failing in these pumps? It seems pretty much mechanical, camshaft driven with some sort of solenoid on the side, I'd assume it's the solenoid that fails. If so, has anyone tried replacing that solenoid or otherwise rebuilding these things? After this new one gets here, I'll have two of these pricey paperweights laying around, it'd be nice if I could do something with them.

Is it more likely that this is being caused by a second failed hpfp or could it be the low pressure, in-tank fuel pump? I can't seem to find too much information on it, it seems mostly like the in tank pump is either working or not, but I figure if the hpfp is being starved for fuel, that would cause the fuel rail pressure to be low, as well, right?

New pump is on, but I had some issues with the install.

Solenoid connector on the new (refurbished) part broke while I was trying to put the connector on. I took the solenoid off the old pump from last year and put it on the new one, hoping that was not the part that fails. It seems to be ok, but time will tell.

I managed to break the nipple/cap on top of the vacuum pump going to the brake booster. Seems like you can't get this part without buying a whole new vacuum pump. Does anyone know where I could source just the nipple connector? I tried to epoxy it back together, but it's about 10°F out right now and it just immediately snapped again.

Well that sucks, might be looking at another fuel pump, then, I doubt the seller will cover any imperfections on a refurb.
I can't tell if the pump is fixed now or not, as the car is in limp mode, I'm not sure if that's because of the vacuum leak or the pump. I'll be trying to jury-rig something tonight to get me by, as this is my daily driver. I did manage to find a used vacuum pump with the cap still on it somewhat cheaply, but I've still got to drive the car until it gets here. The nipple/cap thing is very replaceable, just a T25 holding it on, I just couldn't find one without buying the whole vacuum pump assy.

I did also check the fuel line coming to the hpfp, it didn't seem soft and I couldn't see any tearing or wear on it, so I think the line is fine. Also I'll see if I can find more info on the in-tank pump, it would help if I could find a normal operating pressure somewhere.

I managed to get the vacuum hose attached, at least good enough for the next week or two, brakes are working normally and I don't hear any hissing. I'm not having trouble with cold starts anymore, but now it goes into limp immediately after starting and throws some fresh codes. P3091, rail pressure still low (looks like I'll need another pump) P113B (Not sure what this one is), and P0100 (MAF circuit?). I think it's still freaking out about the vacuum leak, so I'm gonna disconnect the battery for a while and see if they come back afterward.

Yep, looks like that's the case for me, too. *sigh* here goes another couple hundred bucks. Thanks for the help.

Good call on the MAF sensor, my friend, I must have been too concerned with the connector I broke to plug it back in.

Unfortunately, the car isn't faring any better, fuel rail pressure is sitting around 80psi, and it's still going into limp pretty much right after it starts. Guess I'm waiting on that second pump to come in. Made sure to get one with a warranty this time :mad:

I have a good feeling once you have the new pump installed everything else will work its self out. Be careful with connectors. Plastic gets brittle when the temps are this cold as you found out.

Well, the new pump is installed, power is back, and no limp mode. I'm still getting a CEL though, P0088 common rail pressure too high, and P0303, cylinder 3 misfire. I think maybe an injector is clogged, might have to do with all the driving in limp mode I had to do, or it could be causing the early fail HPFP, so I'm running some fuel system cleaner through. I'm not sure what else to do besides start replacing other parts. Could just be an ephemeral thing though, might clear on its own.

Well, fortunately (or unfortunately), the misfire doesn't seem to happen often enough to cause a CEL anymore. Still feels like a miss, but there's no light for it, so I can't see if it follows to a new cylinder. It's been too cold to do much with it lately, but I will order a new pressure sensor and see if that takes care of the P0088. I hate replacing parts at random like that, especially when the car seems to be running fine, but I'm worried that's the underlying issue.

Yes throwing money with the hope its fixes the problem is never fun. If the misfire keeps up trying hooking a scan tool up and have it record the data for you. Pressure sensor could be causing the hiccup/misfire if its giving bad readings

I switched around the coils and plugs just in case the misfire got bad enough to trigger another CEL, which it finally did. It's still only on cylinder 3, which clears the ignition system. If the pressure sensor were bad, I would think the misfire would be on all cylinders, and not just number 3, right? My thought is it's possibly a clogged injector, which I think could cause both a misfire and high rail pressure.