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Random Idle Stumble / Misfire(?) and Hesitation - '04 R53 Cooper S

14330 Views 8 Replies 7 Participants Last post by  Spacemonkey...
Hello, I was hoping somone might be able to suggest some possible solutions to my Mini's random fault.

It's a 2004 R53 Cooper S. Done 80k miles.

It has a Kavs Pulley kit and that's all I can tell you mods wise (the pulley was done before I bought it).

So about a year after I bought it (I've had it 2 yrs in Feb) every now and again while sat in traffic the engine idle would dip - and it would sort of misfire and grumble for a few seconds - I guess till the ECU saw something was amiss and correct it. It does this mostly when hot and been on a decent run. Some journeys it might never do it, others almost every time I queue for any length of time in a traffic jam.

It's never totally stalled when it does this stumble thing, but runs v rough and I sometimes blip the throttle to clear it quicker (concerned about unburned fuel getting in to the cat).

It also seems to have some hesitance sometimes when accelerating, as if it's sort of missing at certain points in the rev range? If I hoof it, it seems to really go, but other times when semi hoofing it, it sort of hesitates and I have to nudge the throttle harder, and once past certain revs it flies...

Now I've lived with it for some time now, but thought I'd do something about it. It is not throwing up any dash lights or anything.

I replaced the plugs, no difference. I bought a 2nd hand coil / leads from a good supplier and no difference.

I had read somewhere that someone back in 05 had a similar issue and they'd said it was the throttle body gasket, and an air leak in the intake tract? Could that be it? See this thread on rival forum...

Might start with this gasket, as its cheap enough? Gasket - part no 2?

Or could it be the two boots/couplers either side of the intercooler - can they cause these symptoms? How would I test if its them?

Any ideas where I start, and how I might test or replicate the issue please?

I am massively skint, and can only just afford the fuel to keep it on the road (how crap is the CooperS MPG!) so the cheaper the solution the better.

Look forward to any help available from those who know these cars much better than me!

David
(Leeds)
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I had a similar sounding problem to this. The car would hiccup and then be fine then a day or so later would throw an emissions code. This happened a couple of times, I changed the plugs from bcr8es to iridiums and I've not had an issue since. The only thing I can put it down to is the original plugs fouling as they were to cold for my general driving (like a granny). The iridiums are much better from cold first thing in the morning as well
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Hopefully you've solved the problem already, but... I had exactly the same problem with my R53 (pulley installed). MSD coil pack (alone) didn't help, but NGK BKR7EIX Iridium spark plugs fixed it completely.
I've got this exact same issue... my revs dip slightly when I accelerate (not full throttle though) and has a lumpy idle.

Plugs have recently been changed.. so thats not the issue... but when WOT it makes no difference.
Check for vacuum leaks in intake, check coil pack terminals and replace lambda sensor if its original
had a similar sounding problem to this. The car would hiccup and then be fine then a day or so later would throw an emissions code. This h
Hello, I was hoping somone might be able to suggest some possible solutions to my Mini's random fault.

It's a 2004 R53 Cooper S. Done 80k miles.

It has a Kavs Pulley kit and that's all I can tell you mods wise (the pulley was done before I bought it).

So about a year after I bought it (I've had it 2 yrs in Feb) every now and again while sat in traffic the engine idle would dip - and it would sort of misfire and grumble for a few seconds - I guess till the ECU saw something was amiss and correct it. It does this mostly when hot and been on a decent run. Some journeys it might never do it, others almost every time I queue for any length of time in a traffic jam.

It's never totally stalled when it does this stumble thing, but runs v rough and I sometimes blip the throttle to clear it quicker (concerned about unburned fuel getting in to the cat).

It also seems to have some hesitance sometimes when accelerating, as if it's sort of missing at certain points in the rev range? If I hoof it, it seems to really go, but other times when semi hoofing it, it sort of hesitates and I have to nudge the throttle harder, and once past certain revs it flies...

Now I've lived with it for some time now, but thought I'd do something about it. It is not throwing up any dash lights or anything.

I replaced the plugs, no difference. I bought a 2nd hand coil / leads from a good supplier and no difference.

I had read somewhere that someone back in 05 had a similar issue and they'd said it was the throttle body gasket, and an air leak in the intake tract? Could that be it? See this thread on rival forum...

Might start with this gasket, as its cheap enough? Gasket - part no 2?

Or could it be the two boots/couplers either side of the intercooler - can they cause these symptoms? How would I test if its them?

Any ideas where I start, and how I might test or replicate the issue please?

I am massively skint, and can only just afford the fuel to keep it on the road (how crap is the CooperS MPG!) so the cheaper the solution the better.

Look forward to any help available from those who know these cars much better than me!

David
(Leeds)
Hello, I have the exact same problem, everything seems to be fine and i do not know where to go :D Can you please tell what was the issue?? Thanks in advance
Hi, first post, but just noticed this so had to reply.

Mine does this. I've only had it a coupe of weeks. I'll copy my posts about it from a rival forum that seems very quiet, and see which I fit in best too!

Anyway, After lots of research I read that it is down to the carbon can that collects the fuel vapours and it purges into the intake somewhere only at idle. Overfilling the tank and hot weather aggrevates it. I've decided to watch my filling (stop on first click) and live with it.
Hi, first post, but just noticed this so had to reply. Mine does this. I've only had it a coupe of weeks. I'll copy my posts about it from a rival forum that seems very quiet, and see which I fit in best too! Anyway, After lots of research I read that it is down to the carbon can that collects the fuel vapours and it purges into the intake somewhere only at idle. Overfilling the tank and hot weather aggrevates it. I've decided to watch my filling (stop on first click) and live with it.
Hi! You still have this issue? If yes, have you changed anything on the car?
Hi, I still have this issue, and I still just live with it. As far as I know, nobody has mentioned a 100% cause or a 100% cure.
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