Mini Cooper , Mystery misfire

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Mini misfire

Hi all,

Any Mini Cooper experts on here, I know it’s an mx5 forum but don’t want to set up an account on another forum for a car brand I know very little about or have interest in.

Friend purchased a 2008 1.4 petrol Mini Cooper with 100k miles, they bought it to replace a Toyota Yaris they rolled and was beyond repair but it turns out the mini although appears to be in good order but has an interesting engine misfire which we can’t figure out what’s wrong, I’m not an expert on these at all.

Car has recently been serviced with new oil and filter , air filter and spark plugs., engine sounds fine with no rattles or knocking noises.

The issue is a misfire on cylinder one and going off this cylinder completely at times at idle, sometimes it recovers and idles ok and is firing on all four then cylinder 1 would drop out again, idle speed 800rpm. Code reader only shows misfire on number one cylinder no other cylinders recorded as a misfire.

Runs fine when cold but misfires when temperature is up.

New spark plugs fitted and have swapped over coil packs plugs between cylinders but still misfire on number one

Swapped spark plugs between cylinders also, no difference.

Removed plug on number 1 and checked and is getting spark.

Compression test good and equal over all four cylinders done with engine hot and with wide open throttle.

When the spark plug is removed comes out wet soaked in petrol.

But here’s where it becomes strange, switch on the air conditioning and increased load adjusts idle to 850rpm and it runs perfectly at idle with no misfire but I suspect it’s misfiring slightly through the rev range as engine light comes on again quickly after resetting this although seems ok when driving I’m told.

Done a Google search and misfires on these seem common but usually can easily be traced back to the usual suspects, plugs, coil packs or bad compression but have swapped these around and compression is good. Vanos solenoids for valve timing being stuck or clogged have been mentioned in some forum threads.

I was thinking bad injector but plug comes out wet and it idles ok with air con on, fuel pressure problem maybe but why would this only effect cylinder one?

One point to note though, my friend changed the oil and filter and said it was filthy and also fitted new rocker cover gasket due to it leaking, does a blocked oil way causing a cam follower to stick intermittently holding valve open sound plausible?

Any ideas?

Many thanks.

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Mini (BMW) changed to the Peugeot engine, from a Toyota unt in the early cars. This unit seems to have a habit of dropping compression on no1 Cylinder. I suggest a compression check

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Hi , compression test looked ok, warm engine throttle wide open, was equal over all 4 cylinders, although now having been supplied with a pic of the camshafts when my friend changed the rocker cover gasket it looks like at some point in the past the engine may have been run without oil changes as the camshafts don’t look too healthy, now thinking valve / camshaft problem.
Engine management light comes on and starts flashing then stays on.

Codes are P0301 and P2169

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Your picture is not very high resolution but on my phone those cam lobes look to be in shocking condition.
Now you’ve done a compression check and swapped plugs, leads and coil packs I’d try a wiring loom, then injector. Swap injectors 1 and 2 over. If you have an injector sticking open it will wet the plug and it won’t spark. So if it’s that the fault will move to cylinder 2. If not it’s a process of elimination.

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Hi again, funny you should mention swapping over fuel injectors friend done that last night, swapped 1 & 3 then drove it round to me and was running fine until up to temperature where fan would come on and then it started misfiring again and still on number one, no difference at all.

Yea I was thinking those camshafts don’t look right at all and would personally like to have a look at them, I’m starting to seriously think it’s valve related, remember old engines where you had to adjust valve clearances and if one was slightly too tight would create a misfire when hot as parts expanded slightly with the heat well the symptoms now that we have swapped everything reminds me of this.
Anyone know if these engines have adjustable valve tappet settings?

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They look like hydraulic lifters to me but I’m no expert. If not they will he bucket over shim type so you have to swap the shims to get your clearances. You have no rockers to adjust in there. Vanos is hydraulic actuation on that engine too if I’m not mistaken.
I’d be more inclined to think electrical fault, you need to monitor via a HSC and a data logger or just swap out parts until it works.

Could be a loom breaking down.
Could be a damaged plug/socket.
Could be the ecu at fault, a transistor failing to fire etc.

Is that engine wasted spark? If so you can do a few tricks as a work around but it’s not ideal, playing with that will result in a slight ignition timing flaw.

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While it was running off number 1 cylinder I pulled coil pack off and using spare spark plug put to earth and spark could be seen.
Turns out we have a mutual contact who used to work for a Mini dealer so going to see if he can provide assistance.
I’m thinking worn valve guide / seal allowing oil into cylinder just enough to fowl plug when hot, have noticed it running ok and revved it starts misfiring shortly after.

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Valve seals letting oil by pass create huge clouds on blue smoke generally.

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I think it might be a bit smokey on start up.

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That’s a usual symptom. Oil seeps past the seals and pools on the pistons then burns on start up. It’s not much oil to cause smoke tho. Ensure it’s blue smoke not white. White is water and normal on cold start. It’s condensation in the exhaust boiling off.

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Tell your friend to get rid.

Older (BMW) Minis are not remotely inexpensive to maintain in the way that a Yaris typically is.
The Minis are just not quality built cars.

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Yea , im thinking he got for to good a price now now having looked at what others of similar age and mileage are selling for.
It’s a 1.4 cooper with about 100k in decent order but I’m near certain he said it was £800. Too cheap now I think.

Hear to many horror stories about Mini reliability.