R56 2007 working on 3 cylinders only, any ideas?

on these engines number 1 cylinder is gearbox end, if have lower compression in cylinder that is dead then its a mechanical issue , common failures on these is valves cracked or carbon built up from stem seal failure,,, on turbo engines they can destroy a piston skirt seen this a number of times when do they smoke like hell,, if no smoke would say its a valve issue most likely so head off,, as you have ruled out plugs and coils what swapping them around,, and i guess the garage would of checked to wiring form ecu to coil ie gets a trigger voltage,, then its rocker cover off then see what you have in there might find its just a cam follower gone south,, but most likely will be head off,

mkov608 said:

Is the check engine light on? Do you know what diagnostic trouble codes (DTCs) are in the computer?

First off, whenever anybody say "probably" run and get a real mechanic to start troubleshooting your problem!
Second, don't let "the probably" guy change any parts on your car!

"The third cylinder didn't work." What does that mean exactly?

How much lower was the compression reading in cylinder 3? You need to post the values for all cylinders.

The engine is easy enough to work on, but you do need the proper tools and technical data.

There are lots of helpful people on the forum, but they will need more information to help you.

What country are you in? I can't make out the flag.

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I'll do my best to answer all the question: the check engine light is not on, he did not hook it up to a computer. Third cilider does not work, meaning that the engine has a rough idle and behaves the same with and without a spark plug in the third cylinder, at least on idle.

The compression in the 3rd cylinder was 6 bar, in the first and second around 9 (if I remember correctly).

I am from Montenegro, which is in Europe. Approx. 600.000 inhabitants in total.

mike1967 said:

on these engines number 1 cylinder is gearbox end, if have lower compression in cylinder that is dead then its a mechanical issue , common failures on these is valves cracked or carbon built up from stem seal failure,,, on turbo engines they can destroy a piston skirt seen this a number of times when do they smoke like hell,, if no smoke would say its a valve issue most likely so head off,, as you have ruled out plugs and coils what swapping them around,, and i guess the garage would of checked to wiring form ecu to coil ie gets a trigger voltage,, then its rocker cover off then see what you have in there might find its just a cam follower gone south,, but most likely will be head off,

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maybe bent valves? Watched this video>


The guy also had issues on the third cylinder. I didn't notice any smoke.

So, about carbon buildup, what would be the steps to check if it's that?

I'm not sure that I follow you? The cylinder that is problematic is the third one from the left

"mike1967 said:
on these engines number 1 cylinder is gearbox end."

mkov608 said:

"mike1967 said:
on these engines number 1 cylinder is gearbox end."

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sure is every time i have rebuilt one or diagnosed one i found number 1 at gearbox end ,, ie like all psa engines,, there is a lot in the bently manual that gets people in to trouble i have found like the missing info on how to do timing chains etc

BMW TIS says the same thing.

mkov608 said:

View attachment 281032

I'm not sure what your technical reference is, but I'd love to see it. Bentley and BMW TIS clearly say that the #1 cylinder is on the timing chain (or front) of the engine. Now if you're considering the back of the engine (tranny side) #1, the firing order would still work the same way; for example, when you performed a leak-down test. See chart above.

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your chart says its both ways going by that,

Right, when you mistakenly posted that the #1 cylinder was at the back of the engine (gerarbox end), I thought to myself. If that's the case, Mile's advice to people would really mess them up if they performed a leak-down test. During the leak-down test, a tech will follow the firing order to save time. But in the case of this engine, even if someone was following your bad advice and started the lead down test on cylinder 4 (which you say is cylinder 1). The leak-down test would still proceed normally because cylinder 2 (which you say is cylinder 3) would be the next one for the piston to come up to TDC and so on through the rest of the firing order. So I built the chart (Firing order 1, 3, 4, 2).

Now you may be right and BMW TIS may be wrong (the #1 cylinder is at the rear of the engine). If you are right, post the technical reference.