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Mini Cooper S Cylinder 2 Misfire

142K views 20 replies 15 participants last post by  Amedeus a.k.a Willie 
#1 ·
Greetings, the other day a PO302 (cylinder 2 misfire) code appeared , so after researching all the threads I could find I started working my way through this. I replaced spark plugs, swapped injectors #2 and #4, swapped cylinder #1 wire onto cylinder #2, chased coil pack wiring back to make sure no chafing of insulation, reset ECU, disconnected battery for an hour, and cleared fault codes in between each of these steps and still the same code rears its ugly head. Now here is the really confusing part, when I swapped the #1 wire over to the #2 cylinder, the #2 wire is not long enough to reach the #1 plug and coilpack terminal so I left it off and assumed it would produce a PO301 fault code but the only code produced was still the PO302. The completely disconnected cylinder #1 never produced a fault code, however the #2 fault refuses to go away. Now this is not just a false alarm as there is a pronounced skip and rough running. I haven't replaced the coilpack because every thread I've read, replacing the coilpack did not solve the PO302 issue. I've been chasing this quite a while now and I could really use a some help. Thanks in advance
 
#4 ·
Compression seems fine, which is good

What makes you think of an ECU problem? personally would have thought a random misfire would be generated if it was the ECU

Here are some links that you may find helpful re: misfires

http://www.mini2.com/forum/first-ge...64976-camshaft-lobe-shattered-faulty-ecu.html

P0304 Cylinder 4 Misfire Detected - Help needed - Page 2 - MiniTorque.com

http://www.minitorque.com/forum/f647/cam-shaft-without-tuning-solution-failed-5284/

I imagine you have read them and spent hours trawling forums as is the case with such problems!

hope this helps and stay sane!
 
#5 ·
Today I took a good look at the ECU. Checked for broken wires/foil and anything that looked unusual on circuit board. Did not see anything wrong put back together and no change to "p0302". I decided to do a little further testing. The current existing problem after I clear fault codes engine starts and idles at about 700 rpm. After say 15-20 seconds, the SES light and DSC light both come on and the engine seems to smooth out a little bit and the idle raises to about 800 rpm, though still running with a pronounced roughness/misfire. I decided to remove #4 spark plug wire from coil to see what fault code would appear. the engine started and would barely idle, (500 rpm or so), running very rough, and no fault code produced. I decided to shut it off as I approached the 1 minute mark. I replaced #4 lead and removed #1 lead and gave that a try to see what code would appear. After 15-20 seconds, p0302 appeared. I cleared that code and removed #3 lead and gave that a try. After 15-20 seconds, p0302 appeared again. I cleared that code and removed #2 lead and tried again. After 15-20 seconds, p0302 again. I'm very confused at this point especially with #4 producing no fault code at all, as if it weren't confusing enough with the other 3 cylinders all saying that they are cylinder #2. I guess I'll keep digging through the forums and hoping some one out there reads this and can shed a little light on my problem.
Again, thank you for your replies and insights.
 
#7 ·
No resolution yet. I've spent the past few days studying the Bentley manual and I am currently checking out any relevant grounds. I dug through all the threads online and I can't believe I have not yet resolved this. The bentley book reads easy however there are about 300 pages of wiring diagrams. I have also looked at recalls and TSB's hoping to find some insight but nothing yet. Thanks for writing back and please if you have any notions or info to share write back as soon as possible.

Thank you
 
#9 ·
PROBLEM RESOLVED!!!!
After chasing out all relevant grounds and swapping around relays and still no luck, I decided to go back to the beginning and verify everything I had already done. I re-checked compression and to my dis-belief, cylinder now had no conpression. I did some serious soul searching trying to figure out how I could have missed this early on, but I knew I had good readings on my first test. My next thought was that perhaps during my 10 miles of driving, hoping a dirty injector or carbon buildup would correct itself, that I had inadvertently wiped out a cam lobe as I have read at least 2 threads where a bad cam had created similar misery to that which I was experiencing. I decided to pull the cam cover and check for damage. Looking as closely as I could, I could not see any damage so to get a better look I decided to pull off the intake rocker arms. I did and as I was peering closely at the cam I noticed 1 intake valve appeared to be sitting a little bit lower than the other 7. Well what do you know,it was the 3rd valve from the left, or #2 cylinder intake valve. I have one of those "See Snake" inspection camera/viewer made by Ridgid with the extra small head so I passed this veiwer down through the spark plug tube and did not see any shiny spots on top of the piston to indicate any collision between valve and piston. Yesterday I drive the hour up to the MINI dealer and bought 2 valve spring just in case I found a second bad one. This morning I installed the valve spring and I just got back from my test drive and all is well again. No more codes, no more misfires, and everything is great again.
I really appreciate anyone's interest in this thread and especially appreciate anyone that wrote me with insights or advice.I hope my efforts will save someone some of the frustration I have experienced in the past 3 weeks.
The valve springs are about $9.00 ea. I bought a valve spring compressor at NAPA because the one you rent at Autozone I could not get to work because the jaws that hook on the bottom of the spring are not staggered to squarely grab spiraled spring. NAPA tool $35.00. I bought the Bentley manual locally because I'm a little impatient, (could have bought it on ebay for probably $90.00 with shipping but I couldn't wait so I paid $115.00).
So all done , about $160 or so.
While picking up my springs at the MINI dealer I noticed their labor rates are $49 to $149 / hour.
I was lucky and hope this info helps someone else.

Thank you
Ribusa:D
 
#12 ·
Hi having much the same problem. ....mines a mini one 1.6 year 2004.....when starting from cold and the revs are over 1000 the engine runs fine....the check engine is on.....when warm, on idle at less then a 1000 revs and after about 20 secs then engine starts to missfire and run rough,the check engine light start to flash....if you turn engine off and re-start ,the miss fire has gone and as long as you keep the revs above 1000 it runs ok.....my daughters car and we been trying to sort it for a year now, in the year its never got any worst just stays the same....today I drove it for 800 miles round trip and as long as revs were above 1k it was fine....returned about 37 mpg at 65....we have changed the oxygen sensor( a used one)....been told its burnt valves. ..but would it not do it all the time?
 
#13 ·
help!

I have a mini cooper s 2008 which has done 88000 miles. It broke down last week and the mini garage have said without stripping the engine back they have no way of indicating what the issues is. They believe it might be the Pistons or the Exhaust valve which has failed but the 2nd cylinder has no compression what so ever. The Spark plugs have only been changed around 3/4 months ago as a part of the service but apparently the plug in that cylinder has been smashed off by something loose in the engine. I have been quoted between £2500/£3000 to fix the issues if it is as straight forward as the above. If not, I am looking at a new engineer for £4.5K. they have only valued the car at £5.5k fully working so are now trying to sell me a new car....

Anyone have any advise or recommendations?

Also - Not sure if anyone else has this problem but my car drinks oil, I am putting around 4litres in every couple of months (apparently this is normal)

Its only just been repaired for an oil leak so expected to see a change in the amount of oil it needs but its not changed!
 
#15 ·
Hello all, thanks for the initial post.

I have a R50 with the same initial fault as the Gentleman from USA, cylinder no 2 misfire, car struggles to run at idle but works out its self there is an issue and idles high to compensate.

I have a compression tester so will test that, so far I have done the plug and wire swop and have a replacement coil pack on route.

I have the ability to read the codes with the simple OBD2 Bluetooth reader, the best few quid I`ve ever spent on car tools. No matter when I clear the fault it returns to I guess there is deffo something wrong.

What are the compression reading supposed to be?
 
#19 ·
You can do this with an airline or the old fashioned way!
What I have done before I had a compressor is to turn the engine until the offending cylinder is at TDC on the compression stroke then reverse it a quarter turn. Now feed a length of thick but flexible electrical flex down the spark plug hole. A couple of feet should do it but obviously leave a good tail sticking out. Now turn the engine so the flex squashes up against the valves holding them shut. It doesn't take much force as your really only holding them against gravity. When your done back the engine off and pull the flex out.

Gerry
 
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