Hi All,

Hoping someone may have a suggestion, before I take the car to the dealer.

Back story: Car brought to me, badly misfiring, with a diagnosis of bent valves in #1 cylinder. I removed the head, and found that one of the intake valve seats had cracked and partially dropped, sticking the valve part way. There was considerable damage to the lifters and variable lift rockers, but no visible damage to the piston, and no evidence of piston to valve contact.

Head was sent to American Cylinder Head for rebuild, where they replaced all exhaust valves, reground the intake cam, new valve seats, and all other damage, and a minimal resurface to the head mating surface to the proper RA.

Re-assembly went well, with new timing chain, tensioner and guides, etc. Mechanical timing set, camshaft adjuster sprockets appear OK, so those were re-used.

Upon initial startup, car idled roughly, showing a misfire on cylinder 1. My initial suspicion was that there was hidden damage to the #1 piston, but a compression check and leak down test showed no issues. Moving coils from one cylinder to another did not change the misfire, nor did moving injectors.

Further searching revealed that someone else had a similar problem, and suggested that disconnecting the intake cam position sensor might pinpoint the issue. When the sensor was disconnected, the engine ran wonderfully. Even momentarily disconnecting, and re-connecting, the engine stays running well, until a restart.

I replace the cam position sensor, but the problem remains. Additionally, I am able to disconnect -either- the exhaust cam sensor or the intake, and the engine immediately runs smoothly.

My last effort to resolve was to verify the camshaft mechanical timing, so I removed the valve cover, and turned the engine over by hand, locking the flywheel, and verifying that the cam locking tools still fit where they were supposed to. They did. (I was almost hoping that one of them was off, even by a little, as that might give the sensor a false reading).

At this point, I'm stumped. All mechanical aspects seem to be addressed, and the fact that it runs so nicely (and drives nicely) after a momentary disconnect of the sensor seems to indicate reasonable mechanical order.

Thanks very much for any suggestions that might be forthcoming. At this point, my next step might actually be a dealer, with their specialized diagnostic equipment. My simple OBD2 tools don't seem to be helping much, other than showing an 0301 (and of course, disconnecting the cam sensor throws that code).

-Darryl

 

So you dont have any faults other then the one from disconnecting the cam sensor? This is odd lol. There is a bulletin to replace that connector but that doesn't sound like the issue. Are you sure the coils and plugs are fine? The only thing that jumps at me right now is the reground cam. Usually after that repair is done you want to reset the DME adaptations and relearn VANOS adaptations. Try swapping the VANOS solenoids and see if the problem goes to the exhaust side. Those are things to just check and do but with the issue on the intake side and all your tests passing maybe the intake cam is bad. That or a valvetronics issue. Definitely let it run until you get a code. Just to check are you sure no wires from the intake cam sensor connector are pinched anywhere?

 

Plugs were changed when I did the head. Changing coils doesn't make a difference.

To clarify, disconnecting either cam position sensor makes the engine run smooth. The intake cam was surfaced/polished for #1, no reground.

You mentioned DME adaptations, which I suppose seem plausible. Perhaps it's time to let the dealer or a mini specialist take a shot...

 

+1 on the VANOS. swap them and see what happens. both parts are the same.

 

Relearn your Valvetronic stops for starters, read any codes stored with a quality reader that gathers manufacturer codes not just generic, reset adaptations, then reconfirm timing, condition of spark plugs and coils, and if all of that checks out I may say you're in for a new intake cam. You can't grind just one cam in a multi-cam system, you've effectively changed cam timing and duration.

 

Just to provide more details: Cam wasn't reground, but polished (sorry, I mis-stated in the original post). Engine runs fantastic if either of the cam position sensors are momentarily disconnected. Plugs new. Coils all check out. Compression, leakdown, fuel pressure all good.

I don't have a decent mini-specific reader, so it looks like a trip to the dealer to have the adaptations and relearn the valvetronic stops.

 

Did you get issue resolved? What was the fix? Having similar issues, thanks

 

More for the benefit of people looking for an answer to their hot idle misfire problem. If you have an n12 engine that is suffering from a hot idle misfire, it is likely that you have a loose inlet valve seat on the cylinder that is misfiring. Why the n12 presents the misfire while the n14 doesn't is because of the VVT technology. In the case of the n14 a loose valve seat results in a destroyed engine while the n12 gives you a warning through the misfire at idle but if you fail to resolve it, the engine will eventually be destroyed. At idle VVT limits valve lift to a couple of mm/very shallow lift, which results in the valve with the loose valve seat not sealing causing loss of compression - resulting in a misfire. When you remove a cam sensor the VVT is disabled and the valves move to full lift at idle (9.5 mm), seating the valve and valve seat successfully and the misfire stops. So if you have a R56 that is misfiring at idle when hot, try disconnecting a cam sensor and if the misfire stops, chances are you have a loose inlet valve seat. A lot of engine specialists are aware of valve seat issues with the R56 however too few people have tagged the loose valve seat issue with the hot idle misfire.

My partner has a justa (n12 Cooper) that had the hot idle issue which we were able to fix, without using the parts cannon! We engaged the services of an engine specialist after a mini specialist demonstrated a total lack of understanding and this is a common problem. After replacing the loose valve seat the justa no longer misfired. At the same time I stopped the dreaded oil consumption that plagues the R56 engines through replacing the scraper rings, went from 1 litre per 800 miles to no oil consumption on a 125,000 engine.

So mini people, please take the time to understand your engine issue(s), possibly talk to engine specialists and not mini specialists with this issue!

Personally, I think PSA Group/BMW should be ashamed of the Prince engine.

 

I had a lot of problems with my exhaust camshaft timing sensor. After replacing, swapping, checking signal too and return signal to ECU, I finally had the DME (ECU) cloned. It fixed my issue. I kept having an alarm, P2986. Exhaust camshaft sensor. I wonder if you have a BMW style reader? When your engine acts up it should show a code. BTW, minitobe reprogrammed my CAS and cloned DME. I was about to lose my mind over this continual issue.
I have an 07 base.

 

Hi Briscoec

I used ISTA - purchased from a supplier on the Net last year, clearly a copy and not original. Did receive INPA as well but never really got that software to work really well with the DME or the other modules. ISTA is the better solution for the Prince engine DME and the other modules deployed in the car.

Have to say your issue is puzzling and why the DME needed cloning - sounds like you are through the worst. If you can get ISTA, it would help you generally, I continue to use it to monitor my partner's mini - mainly for smooth running analysis as we build up the mileage after the rebuild.

Regards


Nigel

 

Well, I had something going on with the old DME. No question about it. As soon as I started the car the code showed. It slowly built up to the continuous error. I think it started with an actual bad sensor. However, I replaced it and then occasionally it would go off when I got on the accelerator. Then it started to go off after I drove it above 20 mph. Then it went off at start up. I can't imagine what this thing was doing or why it was happening. I don't know if I dare give this thing to our granddaughter later this year. I don't have much faith in it. I got a code the other day something with the fuel mixture, engine not running full power. What other car on earth would show that? I'm through the nightmare though.