R53 Most liked posts in thread: Codes for Misfire + EVAP leak, blinking SES

Thanks for the attention you’re giving this, really appreciate it.

Believe it or not, I’m the original owner of this R53. Ordered it to spec and picked it up about six weeks later on Memorial Day weekend of 2004. Two years ago I was prepared to part with it as I decided to go one year older and bought an 03 BMW 540. But my son, who was just turning 16, surprised me by wanting to learn to drive a manual before I sold it. Of course we did that, he proved to be a natural, and there was no parting with it at that point. He was 2 when we bought it and it’s his car now. Pretty cool outcome.

So now we’re learning some mechanical basics (and a bit beyond basic) and having a good time working on it to keep it in good shape for as long as we can.

I think I replaced those damn bushings (at a shop) almost exactly every 35,000 miles lol... and finally wised up and had Poweflexes put in the last time. Thankfully I don’t even remember now when that was but they’re good to go.

Just had my preferred mechanic put new front axles on. I didn’t feel like we had the time to learn that right now. The misfire and EVAP leak codes have been going on but the shop was so busy we just took the car back to troubleshoot on our own rather than leaving it there for another few days/weeks and hundreds of dollars at least while they hunted this down.

I guess I’m kicking myself now because I did not replace the pulley when everything was off for the supercharger service. It looked visually good and normal, like new really, but I didn’t have its age on my radar as a need to replace. Not like I’ll never pull the bumper off again so I can put that on the list.

Ok if you’re still with me, here’s the latest on my original post. Lot of good news - it’s running so well. My son drove it a few times with no rough idling and so have I. I cleared the codes and for the first time in this saga they both actually cleared - for a bit. The SES and ASC lights went off after clearing codes, but the ASC light came back on. Checked codes, and the cylinder 2 misfire code is back. No SES and no code for EVAP leak so that’s half the battle down maybe.

Now I need to figure out the misfire. Worried about bigger problems either causing it or to be caused by it - like a bad cat maybe? I replaced both oxygen sensors a year ago due to rich running codes and that solved the codes. Then we had a cracked exhaust manifold that we had replaced. Like I mentioned earlier today, I have a brand new plug in cylinder 2 and the others are about 8 months old and visually in good shape after pulling them to inspect last night.

Now I’m thinking I may as well replace the wiring harness and probably the coil pack. Of that clears it up, great, if not they’re original and may as well be replaced (cars has 152,000 not 149,000 like I said before. I’m losing miles same as I’m losing track of time it seems).

I have never done a compression test but seems easy to do, can get a tester kit at harbor freight for 50 bucks, seems worth it what with the big old BMW V8 wanting my attention too. That would at least tell me if I should be planning for much bigger issues (piston rings or damaged cylinder or even head gasket even though we don’t have those symptoms really).


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Yep, preaching to the choir on BMW’s “lifetime” line of bull lol... I’ve been sorting some of those things out on the mini and my bmw over the past year.

Plug wires and ignition coils just arrived from FCP so I’ll get those in this weekend. Fingers crossed it solves the misfire, then I can narrow down to the vacuum leak. Who knows.


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Haha I like the full psycho logic... my son is obsessed with the Monster Minis, he’ll probably try to work that angle!

Completely agree with the “while you’re in there philosophy.” I have a lot of research and planning to do next to map it all out and decide on what all those extras should be.

My mechanic basically said exactly what you did. It’s a big job but not incredibly hard, possible to DIY with patience and being organized about all my parts, documenting as I go.

I will be back with a new post to start build thread when we get started. It’s super cold here for the foreseeable, I’m hoping my mechanic can tell me it’s okay to drive a bit longer before digging in. I’d love to give it a few weeks to a month for slightly milder temps out in the garage. But if that could threaten to do additional damage I’ll just suck it up and be cold.


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Spend away!!! I don’t plan to be this deep into the engine for a long time, if ever... want to take advantage and do it right. We enjoy the car and love the idea of giving it a major refresh like this.


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Yeah did that first a few months ago. Similar to the inter cooler boots, it resolved for a short period of time. Maybe a week, then code was back.

Ran okay today, both codes present. Yesterday it bogged down once in low revs after cold start. My son was driving, he shut the car off, started up again and it was okay after that.

Plug wires and ignition coil shipped today. I also replaced the purge solenoid valve (correct name?) the little canister right in front of the engine on the passenger side that takes one minute to swap out. I’d hoped it was the culprit but that changed nothing.

I’m definitely in “throw parts at it” mode which I don’t love, but on the other hand I am replacing parts that have 150,000 miles on them.

You mentioned fuel filter in one of your replies. Thinking that I should consider that as well. But really, I think I have to bite the bullet and set aside the time to pull the bumper and slide the radiator out so I can get eyes on all the vacuum lines. I’m worried about those two rigid ones that go to those red ring connectors, right above the thermostat. I had a hard time getting to reconnect when I was in there. Concerned that maybe I never did all the way.


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Thanks for the encouragement, very cool. I’m excited to dig into it honestly. My son is nervous about it, but our options leave us with little to do but throw more cash at it than the value of the car, part it out and buy a used car that brings someone else’s high-mileage problems, or do as much prep as we can and go for it. He and I both have a few adventurous gear head friends, so between them and you all on this forum and YouTube (and the Bentley guide which I will probably buy) I feel optimistic.

Pretty certain I won’t be throwing any power upgrades at it. High miles on the little lump as you mentioned, plus it is my son’s daily driver, not mine... can’t say I possess the world’s most conservative impulse control, but at 44 compared to his 18, I wouldn’t feel great about the extra juice being under his foot instead of mine.

FCP is my go-to for everything on the mini and my 540. I’ll probably comparison shop a bit more than usual for this job though, so the kinks you’ve both shared so far are helpful. I’ve looked at Detroit Tuned pulleys before, and I’ve bought some accessories from Out Motoring in the past. I’ll be stocking up on several things this time around.


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This is brilliant stuff, thanks for the rundown. I’m on the right track - you’re pretty much describing my plans.

I did since figure out that the kit includes the valve seals and I’ve sorted it out with the shop I’m going to use that I’ll supply those.

I’ve decided that I will in fact put the car in front end service mode. I plan to replace the crankshaft position sensor o-ring and it will be easier to get to that way. I don’t want to pull the supercharger if I can help it. I just had it out in May of 2020 and filled it with fresh oil, replacing the green gasket and the block gasket at that time.

I’m going to put on a 15% reduction pulley to replace the still-original. Thanks for the recommendation on the PRW damper over the ATI. I have been uncertain on that front so far but PRW will be my solution.

I’m going to replace the idler tensioner and pulley too. And of course the belt even though I just put it on last May but I don’t think I should reuse that with all the new pulleys.

I hear you on timing chain. Now I’m not sure. I planned on replacing the chain, both guides and the tensioner. But you make a good point. Thing is the car has always - and I mean from when it was only about two years old - had an on-again-off-again rattle on cold startups that has always sounded like the chain flapping into the guides. The one time the oil pan was off, years ago, my mechanic didn’t see any guide bits in there. My BMW had this rattle too and I replaced the tensioner and that solved it. Possibly that’s all that’s going on with the Mini but at that point I can’t help but think I should pull all of it and start with new parts. They all have 152,000 miles on them. And I would learn how to time an engine to somewhat become prepared for the inevitable timing job on my 540 in the future.

I also already plan to replace the oil pan gasket and the oil filter housing gasket.

The car will be laid up for at least a week or two, easily two full weekends but probably three. Machine shops in my area are slammed right now. Best choice is a guy with a three week lead time. He thinks he’ll be more caught up by the time I get my head to him but still, i don’t expect it back to me with a day or anything. So I’ll be able to take my time, being patient and tackling one of these jobs at a time with no rush or time pressure. Given that scenario, I want to take full a day and do as much of the hard-to-reach jobs as I can while it’s so thoroughly dismantled.

I’ll probably start my build thread here soon and in my first post I’ll include a link to the spreadsheet I’m building of all my parts and prices and sources for ordering. I don’t plan on ordering everything until later this week/next week.


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Super helpful, thanks. I haven’t yet started my timing research so this is a good start to visualize it. So far I’ve understood the timing chain remaining under tension and marking it as seen in the Mod Mini video for the cylinder head, but since I’ll actually be removing it I need to learn those additional steps.

My brand new Bentley manual arrived today so that and YouTube are my best friends for the foreseeable future.


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I’m on the right track, this is great to see your response.

I put the original IC boots back on today and it ran smoothly right away. ASC light is gone, SES still on but I was in a time crunch and didn’t hook up the reader to clear it and see. Will do that tonight.

I put in four new NGK double platinum plugs last May, and replaced cylinder 2’s plug with an identical new NGK last night. And like I said in the original post, I believe I’ve eliminated the oil leak that I had, there’s no fresh oil in that plug well since replacing the valve cover gasket ten days ago. And luckily there was no sign of coolant in any of the plug holes to begin with (so I’m ruling out head gasket I hope?)

Good advice on fuel filter. It is original. Forgot to state mileage... 149,000. As you say, definitely seems a safe bet to replace the fuel filter whether it’s causing any of this or not.

I’m really optimistic about this all being down to the dumb Alta boots. My next step will be to get eyes on every vacuum line and connector, but that requires front end service mode all over again to really see everything (unless maybe a borescope could get under enough stuff to let me see the hidden lines).

Stock and original supercharger pulley. I had the supercharger out last spring, replaced its oil and green gasket, and replaced the serpentine belt. No issues since then until this leak and misfire started. Errors were greatly intermittent at first with no change in drivability - first error appeared four months ago which when I type it looks ridiculous, like I willfully ignored this... just didn’t know where to start until I had worse symptoms, and the possibly related oil leak from the valve cover kicked it all into gear. And now the misfire and vacuum leak is noticeable problem.


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Seems like plug wires are the smart thing to do next. I’ll check out the ATI crank damper too, thanks.


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Could easily be that, seems odd though. I replaced both front abs sensors maybe three years ago, not that they can’t go bad but that the ASC light has been on due to the evap code (I thought).

At any rate, both of our codes are back after one day of clean living. Misfire and EVAP leak. Car is running well though but I figure that’s temporary too. Clearly those intercooler boots must have been a major source of a vacuum leak, and now that it’s well sealed there, the leak is just getting through the next weakest link.

The misfire code came back first and the evap leak was a few hours later in the next startup yesterday. They’re both present at startup today.

Next order of business is new plug wires and ignition coil, was going to do that anyway. Hoping to solve the misfire with that but then I’ll have the vacuum leak to track down still.


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