Service Engine Soon Light - Misfire Cylinder 4 (R53)

[John B]

FYI, I have already read a few threads like this:
http://www.northamericanmotoring.com...inder-4-a.html

But, I have no engine mods except for Nology Wires and NGK plugs. 2005 Cooper S with only 31,500 miles. Have owned the car for four months, previous owner never had any trouble like this:

During normal driving, yellow "service engine soon" light comes on, and engine runs on what feels like either 3-cylinders or "limp home mode". It will barely accelerate on flat roads (also the noise of 3-cyl & running a bit roughly), and will not accelerate at all up slight hills (well, at least not with 3 people in the car and flagging gear). First time it happened last Friday morning on my way to Road Atlanta, I pulled off, turned off engine, wiggled the plug wires at both the engine and the coil, started back up, ran fine, but light was still on. Light goes off after 20-30 minutes. Again last night, four days later, it happens again. This time I take it to may local shop (specializes in imports, not a Mini dealer) and he hooks up an OBDII scanner and sure enough it says "Misfire Cylinder 4". He said he "cleared the code", but light is still on, but runs fine.

Anyone else heard of this happening? Was it fixed by replacing just the spark plugs? What is the worst case scenario that this would cost (ballpark) to fix, you think?

Thanks all!

[davisflyer]

My dad's R50 had that code and he ended up needing a new cylinder head. Luckily it was under warranty.

[NightFlyR]

Are you sure the plugs are in correctly, it is possible you blew out a plug if you crossed threated it when putting it in.

[herbie hind]

check coil for corrosion at tips . clean with scotch brite pad . add dialectric grease . check plugs (pull them from COLD block ) for oil fouling #4 or antifreese . is coolant being lost ? does dip stick or filler cap have whitish goop on it ? back to plugs ; place a fresh plug in #4 hole to eliminate plug issue or swap with another hole and see if code moves . not sure how much time you wanna spend trouble shooting . if you find nothing ; you'll need compression test to see if you got a burnt valve . i had persistent problem with misfires but was on acceleration and turned out to be aftermarket coil .coils are tough cause when cold they can appear good then when hot they open . best way is a swap if you can get hold of one . if the issue is constant ;put a plug in #4 wire and see if it sparks if not it's the coil .

[go_mini_go]

Check the easy stuff first, check for damage to electrode on plug or excessive fouling, pull plug and check for spark. Then start ruling parts out.

First, swap the plug #3 to 4. Drive car, see if misfire moves to #3. If so- replace plugs. If not, swap plugs back to original location.

second, do the same procedure as 1, except swap wires this time. See if misfire moves to that cylinder, if so replace plug wires.

If neither of these leads anywhere, swap coil with another car.

My wife's Benz had a terrible misfire, plugs and wires and a gajillion dollars later, it was Mercedes smooth again.

[hoping2keepit]

I had this with my 05 MC (about a year ago, I think.) Yellow Check Engine light, and the engine running in "don't let the idiot driver destroy me" mode. It was a bad spark plug in my case -- while we were at it, we went ahead and replaced the cables too since it was fairly cheap & easy.

[joey1320]

do a quick compression test, you should have around 125-130 psi per cylinder. keep us updated.

[John B]

I took out spark plug #4 and it looks healthy. I DID notice that the boot at the coil for #4 doesn't seem to be seating properly, even when you push very hard to get it to stay in its place. I am going to go ahead and replace all the plugs and wires since they have 15k miles on them, anyway. If it keeps up, I'll let you know.

Thanks to all for your help!

[herbie hind]

15000 is nothing for wires . ohm out all the wires ; they should all be close to same . if #4 is way high then you got the culprit . otherwise it's a waste of money. the stock wires are very good .

[minimom09]

we have a 03 mini, not an sc, it has a service eng. lite on along with stability control lite.we had the car scanned and it has a missfire cyl.#4.we have replaced spark plugs,wires,and coil,and cleared codes.but after you drive about 20 to 30 miles,it has the missfire code return and it starts all over again,has anyone ever had this ongoing problem and been able to fix it,please help!!!!!!

[pizmo pete]

Hi, I have a 2002 JCWS 63,000 fun miles.I had this happen to me after changing to MSD coil, wires, and brisk silver plugs...drove car for weeks ran fine then sputter lights and misfire code. Thought first it was bad Mobil gas(hate Exxon/mobil) put in dry gas etc. checked all connections to plugs, looked fine still sputtered. Put old coil back on since the next trip was to the DEALER uggh! started car, no sputter ,smooth idle. WTF this was a new coil and I didn't think it would go in a month. And cause a mis-fire?

[mini1w]

I've got the same check engine issue with 1 cylinder getting shut down.
Took it to a shop and they found low compression on one of the cylinder.
They want 2500 to rebuild the top end, (could be rings, could be vales, could be valve seals) :(

[minimom09]

Bingo, it was cylinder 4 issue, had to replace. BMW says a common problem when regular gas is used, we've had car almost a year and used premium, obviously previous owner didn't. Thanks for all the help. Spent big bucks now's mini is happy.

[shayo]

Hi,
have you figured out your problem? Please let me know as I am having the the same problem with cylinder #3

[minimom09]

Yeah it's figured out, the problem was bad cylinder head - they told us the previous owner probably didn't use premium gas cause regular gas will cause this problem. They replaced cylinder head and valve with a couple other minor parts, grand total $2600 parts and $1600 labor - yikes! but it does have a two year warranty : )
Good luck. Minimom

[shayo]

I'm sorry to hear you had to pay so much. Mine doesn't seem to be engine problem because we tested everything but we don't know what causes the engine light to come on.

[minimom09]

Honestly we didn't think it was the engine either, the car ran great, at some point usually 20 miles or so when you come to a stop light it would idle rough, check engine and stability control light. This would pass and the car continued to run fine but light didn't go out until reset. My husband is mechanic - unfortunately not a BMW mechanic. He checked head compression and it was way down so we were pretty sure before we took it in. Car has more power now so obvisouly its been bad for a while but the lights only started coming on for the past month or so.

[shayo]

Hi,
I checked compression on all cylinders and all very good compression.
Some people have mentioned oxygen sensor. Any idea?

[Cadenza]

Originally Posted by minimom09

Yeah it's figured out, the problem was bad cylinder head - they told us the previous owner probably didn't use premium gas cause regular gas will cause this problem. They replaced cylinder head and valve with a couple other minor parts, grand total $2600 parts and $1600 labor - yikes! but it does have a two year warranty : )
Good luck. Minimom

How does using regular gas damage the head? And how did they know the previous owner used only regular gas?

[ZippyNH]

It is not rocket science.....lower octane gas in an motor can cause pinging and dentonaton....both of these are very dangerous to a engine....detionation in seconds, pinging in the longer term. Both result in very high tempeture+pressures in the combustion chambers....causing wear, in excessive amounts to the pistions, rings, valve, and possible causing the head to crack, and setting up the motor for a failure of a crank, etc. Basic engine stuff...it has been endlessly debated in many threads, but opinions cannot change physics. Your motor requires 91 octane (us rating system), use it, or major and $$$$$ repairs will eventually result.
The first time a shop shows you a melted pistion, or one with a hole in it you will believe. The computer has some tricks, like retarding the timing to prevent dammage, but these should be considered a short term way to deal with a single tank of out of spec fuel.
Now, spendind $2 more per tank of gas sounds cheap....compared to spending $1600 for a valve job/ major engine repair!!

[atiannicelli]

I appear to be having the same problem with my 2005 Mini cooper. It has 105,000 miles on it and a couple months ago I felt it missfire when accelerating on the highway and the check engine light came on. I took it to autozone and they read the code. It said that there was a cylinder 1 missfire. When we took the plug out of cylinder one we noticed oil on the threads. The guy at auto zone said that was bad. I replaced the plug and things seemed better. Then it just happened to me again and when I read the code it said cylinder one again. I replaced all four plugs this time and cylinder 1 and 2 had oil on the threads and cylinder 3 and 4 were clean. After reading this thread I'm wondering if I need a couple new cylinders or maybe just valves?

I've used 87 octane gas for all 105,000 miles so I believe that the $.25 a mile extra still works out to be a deal if I have to spend a couple thousand on it now... Not that I want to, but I will see how it behaves in the next couple months.

[HRM]

I think you mean $.25 per gallon and at 25 mpg, that is $1050. Anyway, you need to get a mechanic to take the head off and see how bad it is. A gasket will be a win, more than that a loss.

[Anya'sMini]

I have the exact same problem with my 2006 Mini. Any suggestions? Did the compression test - all good, changed the plugs - the problem went away for two days then came back again. I also have the DSC light come on randomly and stay on untill i restart the car.. Frustrating!