P0300 Fault Code

[Hagar46]

My Service Engine Soon (SES) light has been coming on and staying on for long periods of time (it will turn off occasionally on it's own). The code reader showed the dreaded P0300 intermitant misfire code on cylinders 3 and 4. I checked all the likley culprits, plugs, wires, coil, etc. and it did not go away so I took it to Baron MINI. They kindly diagnosed the problem at no charge. They verified the cylinder 3 and 4 intermitant misfire and did a compression test. They said I had low compression in cylinders 2 and 4 (this is causing the computer to either not fire the spark plug or not inject fuel in cylinders 3 and 4) and that I needed to have the cylinder head resurfaced at a cost of $2,450 (they think the head is warped). The car is not worth more than $5,000 so I did not have them do the work. The car seems to be running fine in the meantime.

So I have a couple of questions for the more mechanically astute club members. Not to second guess Baron's diagnosis (but I suppose I am curious), could low compression in 2 and 4 cause misfire in 3 and 4 or might I have more than one problem? If I do need the head resurfaced, any recommendations for a shop that might do it cheaper? Any other thoughts?

George

[Minidave]

Warped head? That about the oddest diagnosis for low compression I've ever heard....

Has it overheated?

Is it losing coolant?

Is it burning oil?

If no to any of those questions, I'd be more inclined to think you have a couple of burned valves, and resurfacing the head would be part of a complete valve job. I also don't think it should cost $2500 to do a valve job let alone resurface the head, in fact, not more than $1K - even at Baron. Maybe they were just going to put a rebuilt head on for that money?

Maybe I or you misunderstood them?

However, I'd be very careful about what shop you use to actually do the work if you do, there are legions of threads about shops who said they could do work and then the owner wound up needing a new engine shortly after due to incompetence. I'd start with phone call to KC Autosport and go from there - if they haven't already done several valve jobs successfully on MINIs, I'd look for another shop.

Part of the problem is, with as much mileage as your car has, where do you stop the work? Just a valve job? What about the timing chain? It would probably be a good idea to replace it too...and the plastic slides and tensioner......and jeez, while you have the pan off to do that why not replace the rod bearings, they're right there in the open.....and since you have the head off and the rod caps off, might as well slip the pistons out and put some new rings on them, of course you'll need to at least hone the cylinders first......see what I mean?

The one thing you can be sure of, it's not going to get better if you leave it alone....

[Hagar46]

No misunderstanding. Its even written on my ticket. Not overheated, not losing coolant or burning oil. Burned valve sounds more like it to me too. But motor is running fine. Maybe the computer is smart enough to compensate some for low compression but cylinder 3 and 4 misfire?

I thought of calling KC Autosport too. And yes, I could spend many thousands more to bring it back to tip top shape but probably not cost effective. Anybody want to sell me their used Cooper S w/automatic? Haha!

[Minidave]

That's very strange.....

Since it's a 4 valve engine, you could have 1 exhaust valve one two different cylinders that's just a bit burned and not sealing perfectly and it will still run mostly OK. I don't think the computer knows what the compression is (or isn't), it only reacts to emissions and voltage coming off the injectors or ignition.

I think you need a valve job, maybe check with Way Motor Works to see if they have an exchange cylinder head? That would be the quickest way to get it back on the road, although not necessarily the cheapest.

[Hagar46]

Way Motor Works has ported and polished heads starting at $2,400. They have an entire used R50 engine for $2,000 but they said they don't sell just a used head.

[Zack]

Way Motor Works has ported and polished heads starting at $2,400. They have an entire used R50 engine for $2,000 but they said they don't sell just a used head.

Here ya go. Used Cooper and Cooper S's with Auto in your area
(2008 Cooper S)
http://www.autotrader.com/cars-for-sale ... 9857&Log=0
(2005 Cooper S)
http://www.autotrader.com/cars-for-sale ... 1037&Log=0
(2005 Cooper)
http://www.autotrader.com/cars-for-sale ... 3244&Log=0

[Counterfit_Mini]

No misunderstanding. Its even written on my ticket. Not overheated, not losing coolant or burning oil. Burned valve sounds more like it to me too. But motor is running fine. Maybe the computer is smart enough to compensate some for low compression but cylinder 3 and 4 misfire?

I thought of calling KC Autosport too. And yes, I could spend many thousands more to bring it back to tip top shape but probably not cost effective. Anybody want to sell me their used Cooper S w/automatic? Haha!

I might sell you mine LOL

[Hagar46]

Thanks, Steph, but yours is too nice and new and out of my price range!

[Counterfit_Mini]

Thanks, Steph, but yours is too nice and new and out of my price range!

The dealer will only give me like $14,000 for it. LOL

[Zack]

Thanks, Steph, but yours is too nice and new and out of my price range!

The dealer will only give me like $14,000 for it. LOL

Steph that's a good deal. You could put that towards a nice new Clubbie

[Counterfit_Mini]

Thanks, Steph, but yours is too nice and new and out of my price range!

The dealer will only give me like $14,000 for it. LOL

Steph that's a good deal. You could put that towards a nice new Clubbie

I owe over $16,000 on him

[Zack]

Ouch. I think MY wallet just yelped in pain.

[Counterfit_Mini]

Ouch. I think MY wallet just yelped in pain.

Yeah. It's because I drive too much and I'm already out of warranty in less than 3 years.

[Hagar46]

Update on the P0300 code. I took my car to KC Autosport for a second opinion and I'm glad I did! They concurred with the periodic misfire and did another compression test. They, however, determined that all four cylinders had good compression, 195, 201, 176, and 195. So I don't need re-surfacing of my cylinder head for $2,450. KC Autosport replaced my new Iridium spark plugs with stock plugs and so far, so good. The Iridiums were improperly and irregularly gapped causing the misfiring. Once again, when things don't seem right, get a second opinion. Here's hoping that this is the fix and I can drive my MINI another 8 years and 170k miles!

[Zack]

Update on the P0300 code. I took my car to KC Autosport for a second opinion and I'm glad I did! They concurred with the periodic misfire and did another compression test. They, however, determined that all four cylinders had good compression, 195, 201, 176, and 195. So I don't need re-surfacing of my cylinder head for $2,450. KC Autosport replaced my new Iridium spark plugs with stock plugs and so far, so good. The Iridiums were improperly and irregularly gapped causing the misfiring. Once again, when things don't seem right, get a second opinion. Here's hoping that this is the fix and I can drive my MINI another 8 years and 170k miles!

How much was the cost difference? I have a resistor failure in my cooling fan and was told it would be either around 450 to replace the resistor or 750 to do the whole assembly. (This was at Baron)

[Minidave]

That's great news, George. Good to hear your MINI is hanging in there for another 200K!

[Hagar46]

Ongoing update. Spark plug change seems to have done the trick. No more SES light!

[Zack]

Ongoing update. Spark plug change seems to have done the trick. No more SES light!

Sounds like the mechanics at Baron need more training to look for the obvious problems.

[Counterfit_Mini]

Ongoing update. Spark plug change seems to have done the trick. No more SES light!

Sounds like the mechanics at Baron need more training to look for the obvious problems.

Yep.

[Hagar46]

Update: Just completed 3600 mile, five day round trip of the western USA with one of my dogs to visit clients in Sacramento and Santa Fe. MINI ran perfectly at 80 mph all the way. No recurrence of the SES light so KC Autosport got it right! I'm good for another 170k miles!