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Discussion Starter #1
Hi all,

I recently bought a 2006 Cooper S JCW from a friend. It's had issues in the past but most things rectified by him.

Sods law, shortly after getting it home I got a couple of error lights - DSC and emissions. Since then I have had nothing but issues. I think it's easier if I give a summary!

Issues I've noted:
1) DSC and emissions warning lights come on when warm and idling (rarely when driving)
2) P0304 and P0172 errors thrown by the OBD
3) Occasionally will switch to running 3 cylinders at idle until restarted
4) Quite loud throttle-dependent hissing from left side of intercooler (not the rubber boots though - they seem fine)
5) Lots of oil in the spark plug 3 & 4 tunnels and around the bottom of the valve cover.

Things I've tried:
1) Clearing codes and trying again
2) Swapping various leads around
3) Replacing all the spark plug gaskets and the valve cover gasket (no more oil leak - hooray!)
4) Injector cleaner
5) Checking valve springs - all seem fine

Things I think it might be:
1) Spark plugs but that's too easy and the current ones look fine
2) Cylinder 4 exhaust valve dead
3) Vacuum leak somewhere - the hissing from the intercooler?
4) Dead coil pack / spark plug?
5) ?? cylinder 4 injector

Little bit at the end of my tether for today and would really appreciate some help diagnosing the problem. I don't feel like it's an electrical issue, particularly as it seems to run fine when not idling. I've tried inspecting all the tubes around the intercooler but there's nothing obviously split - can an intercooler itself crack and give this issue?

Really would appreciate any help you can give!

Thanks
Tim
 

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Hi Tim, welcome to MT. Typical culprits for 'stuff' are corrosion on the coilpack terminals (typically number 3) and the vacuum line for the fiel pressure regulator perishes and falls off. But if you can hear hissing I'd definitely give the boots a proper check
 

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intercooler can crack, pipe as suggested maybe, fuel pressure regulator pipe connects that side, air leak can cause dsc light with eml but less likely the same cylinder misfire, these lights with misfire can indeed be plugs, certainly don't trust BKR7EIX even if recent, had this on my own car with recent plugs and low miles, it's not the exhaust valve or it'd be permanent ;O)
 

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Discussion Starter #4
Wow, responses already. Thanks so much to both of you.

I'm happy to give swapping the spark plugs a try but I really don't feel like it's that giving the problem. I'm not sure why. But I will try tomorrow.

Re: the hissing sound, this genuinely seems to be coming from the intercooler itself, just to the left of the centre of it. There seems to be 2 pipes beneath that point- the fuel pipe which is fine and a yellow-ish air pipe which looks fine on inspection. No cracks or splits. Is it common for the intercooler to crack?
 

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I'd swap the injectors around also while you've got the intercooler off.

The edges of the horns and the 'cooler are pretty sharp, so it's possible you've cut one of the boots of its been on and off a few times.
 

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If you take off the inter cooler then check the plugs are nice and tight, even when torqued down properly plug number 2 always seems to get loose.
 

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Wow, responses already. Thanks so much to both of you.

I'm happy to give swapping the spark plugs a try but I really don't feel like it's that giving the problem. I'm not sure why. But I will try tomorrow.

Re: the hissing sound, this genuinely seems to be coming from the intercooler itself, just to the left of the centre of it. There seems to be 2 pipes beneath that point- the fuel pipe which is fine and a yellow-ish air pipe which looks fine on inspection. No cracks or splits. Is it common for the intercooler to crack?
not common but possible, pinched boot below is reasonably frequent, the yellowish pipe may be the grey pipe from the PCV valve which goes to the charger intake tube.

noises around the pulley area or the charger exhaust horn can be a number of things, including a dry supercharger PTO which transmits a hissing/scraping type sound up the left horn which can be quite audible,
 

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Discussion Starter #8
Thanks everyone again for all the input - nice welcome to the forum!

Plan of action today will be to
1) Swap around some spark plugs and see if the misfire moves
2) Swap around an injector and see if the misfire moves
3) Recheck (again) the intercooler boots

After that I'm running a bit short of ideas.

Just to say again - that hissing noise seems to be coming directly from the intercooler. Left side, about 1/3 of the width inwards from the boot, about halfway between the top and bottom. I can get my ear right to it. The pipe below looks good but I can wrap it in self sealing tape and see if that helps.
Honestly I think the easiest thing would be to swap it out with someone else's intercooler and see if it stops doing it! Anyone in Cambridge fancy giving me a hand?!

Thanks all again - really appreciate it./
Tim
 

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one test is to spray a little of something like easy start or brake cleaner only when the engine isn't too hot, and see if the engine reacts suddenly which is one way to find an air leak, don't spray anywhere near the exhaust just a little by the I/C area at first, such stuff is volatile!
 

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Discussion Starter #10
Okay so spent some time on it today. Findings:

1) The intercooler boots are definitely not torn or leaking.

2) Swapping the spark plugs around seemed to make it last longer before throwing the codes - I managed 50-odd minutes code free this time before 'Cylinder 4 misfire' and 'System too rich Bank 1' reappeared - again after idling for a while when warm, which is the pattern that has developed. Also the too rich warning fault comes first, prior to the misfiring.

3) I didn't get time to take the fuel rail off and swap the injectors around. Plus I'm not really sure how to do it.

I did however make a video of the noise, which might help you guys help me diagnose it. Again this sound seems to be coming directly from the intercooler:


Any further thoughts? Could a leaking intercooler give these problems or is a red herring? Desperate to get to the bottom of these problems, they're driving me nuts!
 

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Discussion Starter #12
Secondhand intercooler only about £20. Maybe worth a try.
Agreed. But I still can't get my head around why that would cause rich fuelling followed by cylinder 4 misfire.

Slowly getting closer to giving up!

What do you think I could try next?
 

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as above I'd swap the I/C but I'd still spray it first, if that's leaking how it sounds you'd get an instant reaction from the engine

if unaware the top end noise shouldn't really so prominent either, these engines run pretty quiet bar injector sound
 

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welcome to MT, don't give up it's a Mini, once you've found the problems and get it running you'll be smiling from ear to ear :thumbup:
daft I know, but have you checked all your levels, Oil, coolant, are the fans kicking in, if so at what temp?
you say moving the plug leads helped, maybe the problems lies here -new plugs, leads, have you checked compression, is it running rich all the time, can you smell fuel?
have you tried soapy water on the pipe work / I/C to check for leaks or do a smoke test
Did the Old owner experience the same problems as you're having...have they just started...did you or he change anything recently
Maybe time for a good health check at a decent tuners garage
good luck and let us know how you get on
 

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rich signal is the lambda trying to compensate for an air leak

misfire may be a consequence but you can't really look further until the air leak is tested and/or fixed,
 

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probably just the cam sensor or crank sensor and lambda or potentially coil if resistance is different
 

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Discussion Starter #18
Completely on board with changing the intercooler, but I can't understand how an air leak from that would cause overfuelling and misfires at idle? Wouldn't a leaking intercooler lead to less power when giving it the beans?

Also yesterday another code to add to the list! P1109. So I now have P0172, P0304 and P1109 to work on! Does that help at all?

Thanks for the encouraging posts..! I'm keeping going (for now)
 

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My understanding (which may be flawed) is thus.

At idle the car is sucking vac on the inlet, that lets more (unmetered) air in, the Lambda sensor detects a lean mixture & over compensates with more fuel.
 

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Discussion Starter #20
Wasn't the intercooler. No change in the noise or error codes with a different one on.

Took it for a longish drive today and noticed a new symptom - the fan heater doesn't work. Could the thermostat be the cause of all of this?
 
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