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R50 Misfire - Head Scratcher

9K views 33 replies 4 participants last post by  Ted Westwood 
#1 ·
Hi Guys,

I know this is one of those things that varies from case to case but I wondered if anything strikes a bell with one of you.

My R50 cooper has been misfiring for a bit now when cold and running initially through gears 1 and 2, hesitating on accelaration - before disappearing. Sometimes it takes a few moments to start, but always manages to. Usually occurs after a significant period of time passes, 8-9 hours after switching the engine off, never after just a couple of hours. Idle is a little rough too but I have got a vibration on the bonnet which could be a contributing factor. I will look at sorting that out. Anyway...

I went through the process of replacing the usual suspects, it didn't misfire at first so I switched the battery (needed doing anyway) and then when the misfires started I also did the plugs, ht leads, coil pack, put some redex through the system etc. My levels are also fine. I had Minisport in Padiham do a compression test which showed up clear and gave me a lot of relief. The plugs have been white, showing it's running lean. Bizarrely, it disappeared after they took the plugs out, coil pack and leads off I had no symptoms again... Symptoms started up again however...

Recent other work (past few months) that has been done is a new crank sensor O-ring, a service (oil, filters), new exhaust.

I've tried running a diagnostic on it but no faults have been stored, maybe nothing is showing outside of "healthy" values. I don't know what I'm looking for as regards to live data though. It's never had an EML..

I did have a realisation the other day however, I had two slow starts and misfires when I was low on fuel (1/4 tank perhaps). In addition, on a fairly full tank this morning when I was rushing I backed out of my girlfriend's drive way and into first quickly causing a significant hesitation on acceleration, there would have been a lot of motion in the fuel system with that. With all this into consideration, might it indicate a fuel pump? That might explain the lean condition of the plugs and why symptoms "disappear" soon after start? Although it is bizarre that these things don't appear in the diagnostics?

What'd you reckon?

Cheers,
Ted
 
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#2 ·
Hi Guys,



I did have a realisation the other day however, I had two slow starts and misfires when I was low on fuel (1/4 tank perhaps). In addition, on a fairly full tank this morning when I was rushing I backed out of my girlfriend's drive way and into first quickly causing a significant hesitation on acceleration, there would have been a lot of motion in the fuel system with that. With all this into consideration, might it indicate a fuel pump? That might explain the lean condition of the plugs and why symptoms "disappear" soon after start? Although it is bizarre that these things don't appear in the diagnostics?

What'd you reckon?

Cheers,
Ted
Hi Ted,

What a relief to read a detailed post for a change rather than the usual pish we get on here! I think you have narrowed the fault down to where I would have it narrowed to also. I'd now maybe change out the fuel filter and see how you get on with that, failing that then I'd be looking at the pump. Here is a video on how to swap out the fuel filter.

Keep us posted with your findings buddy.
 
#3 ·
Hi Sean, not a problem, thanks for replying! I'm glad you're at the same thought as me. Hoping it's the filter and that the pump survives otherwise I'd be looking at an expensive replacement or a second hand OEM no doubt?!

Do you, or anyone else, know which filter/where to buy such a filter from? ECP nor Halfords appear to have a part relating to an R50. I'm finding:

- "Topran" filter - Amazon - £14.49
- A "Vaico" filter - eBay - £16.20
- An OEM filter - 1320 - £29.46

I would give the links but I cannot post URLs due to being a new forum member.

What'd we reckon?
Ted
 
#4 ·
Here is the filter Ted but I think very early R50's have a sealed pump so the filter can't be changed but don't quote me on that? Maybe someone can confirm this but in any case it may be best to double check yours before you order the part? Remember to depressurise the system first to save making a mess.
 
#9 ·
Cheers Sean! This might be the giveaway without having to do any opening up - apparently the purple arrow is where the fuel filter is accessed, the red for the pump.

I'll probably order the filter regardless so that when I have a chance to sort it (if I can) I can do the check and change all at once. If it doesn't have one I'll send it back. Probably shouldn't do that with the pump, not sure many places would allow me to send it back!
 

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#18 ·
The 2001 registered cars had the sealed filter your 02 car will have the proper filter housing.
So the two - should - be separate as in the video and various other sources? Two of you suggested that the filter would be inside the pump?!

I had another misfire today a few seconds after start, into second gear accelerating slightly uphill and around a corner.

Surely this is all going to have knackered the pump by now, could the filter really have so much of an effect as to cure the problem? Reasonably? If the two are separate at least anyway.

Would you guys ever buy a second hand oem from eBay rather than a aftermarket replacement from EuroCarParts? Just considering the worst case options.

Should I check the injectors too before a potential change? Anywhere I can get them at a decent rate? A single Bosch injector is like 100 quid on ECP...

But I'm obviously hoping for the best and holding out for the filter to remedy it. I should be able to spare the time on Friday to make the switch.
 
#26 ·
It's one of those wifi ones, but I tried someone else's hardware one a number of weeks ago and had nothing.

Swapped the filter out last night, car started fine but didn't have any time to spin it round. I assumed all was fine. Unfortunately I got in this morning to go to work, started with no problems then it misfired and hesitated all over the place to begin with, more so than usual. Then when that stopped, the efficiency was well down, in the teens, and a general loss of power (I think). No codes.

Have I put a seal on poorly? Has the filter gone in the wrong way round? A mechanic suggested to me I might have done, but I swear there was no orientation on it....
 
#32 ·
Hi Ted, diving in on this a little late in the thread but my R50 had what one would call a misfire issue, no EML lights and plugs, lead and coilpack replaced, seemed to sort it and again, at sporadic times, the car would misfire and hunt. Being old school, I thought it felt more like a fuel issue. My R50 had the old style fuel filter (sealed unit) so as it is no longer in production, I had to replace with the newer replaceable filter type. Its a straight swap over with no issues, just a plastic body with replaceable filter that's all. Problem sorted for 2 days then worse than ever, turned out to be a worn out fuel pump as well. Whilst an expensive exercise for the new filter unit and fuel pump, the issue was sorted.

Something to consider, you can hear the fuel pump initiate when you turn on the ignition (don't start the car) and the whine should be constant and drop off once the system is under pressure. If you have a blocked filter or worn fuel pump, you will hear the whine fluctuate, especially when you have what one would consider to be a misfire (its actually fuel starvation). I ran the car with the rear seat base out for several days while diagnosing the issue and again for a couple of days after the new filter and pump were installed so I could hear the fuel pump whine and monitor it. With no vapour leaks and a nice humming pump, rear seat base went back in and the car has not missed a beat since (2+years and 65000kms).

Forgot to add, if you have a leak (start the car before your replace the filter/pump covers) your going to see fuel spray around the connections to the filter, failing that, your not going to get pressure and will have an error light (same as having the fuel filler cap off).

Made a PDF while I was sorting my R50 so hopefully it may be of some assistance. Here is a dropbox link where you should be able to download the document in PDF format. https://www.dropbox.com/home/Mini C...+Replace+Mini+Cooper+R50+Fuel+Filter+Unit.pdf
 
#34 ·
Problem with the fuel filter solved, efficiency is slightly better. I ordered another filter and set of o-rings/gaskets. Still got my elusive problem though.

One of two possible reasons:
- I cocked up on the fitting the first time, either the gasket or the big thin o-ring. The o-ring snapped when I tried to reseat the two parts of the housing.
- The first replacement filter was ever so slightly taller than the OEM (and I'm talking a mm in it or so here), whereas the second replacement was the same size as the OEM. When fitting the big thin o-ring, this might have been enough of a difference to allow it to sit properly.

If the second reason is the one, then I'd order the VAICO filter over the Topran, it's ever so slightly shorter.

Thoughts?


And awesome Milpol, it's nice to hear you had the same symptoms as me. I'm taking it into the garage on Tuesday for a diagnosis, so I don't have to replace it only to find it hasn't solved the problem. I'm also suspecting the cat could be a problem. What'd you guys reckon?

I can't view your dropbox link by the way, it appears like you've sent me your personal link rather than the public link.
 
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