My 2002 R53 has developed a problem whereby occasionally, while sitting at a stop light, the car will act as though its about to stall. The car never does stall and will go back to a regular idle after 10secs or so, or if you tap on the gas it returns to normal immediately.

A further issue, although i'm not sure if this is normal behavior, is that while sitting at idle the car will regularly vary RPM between 700 and 1000. The car sounds better at 1000 than it does at 700 - at 700 it sounds like a precursor to the stalling behavior. The graph below was record from an OBM sensor I bought to diagnose the problem, but I'm not sure what data channels I should be looking at so I just showed timing advance.

I have new plugs and coil on order (for lack of other ideas). Car has 90k, so due for plugs anyway.

Anyone experienced this before or got any advice??

 

Mine recently started doing it after being modified. It happens upon cold start, let it sit for a couple minutes and it quits.

 

My car was acting similarly but was also illuminating the service engine soon lamp. The code was 1498. I noticed that the rubber boots on the intercooler were looking cracked so I replaced them. While working on that I noticed two disconnected vacuum lines under the intake manifold on the driver's side. I replaced the lines and have not had any trouble since.

 

I have 2 03's and they both do it.

 

same problem on my r55 jcw. I have a thread about it, and I will post anything that I find out in that thread in here in case anyone needs the information.

 

Thanks all for your responses. To clarify, it happens to me not just after a cold start, but even after the car has warmed up. No CEL or codes thrown either... Just a change in rpm and sound of the engine at idle.

I had it at a mini shop a few weeks ago and asked them to check the timing - they said they didn't hear anything unusual.... :/

Good advice on the vacuum lines - will have to read up on where they are (and what they look like!).

OldGameFreaK - did you ever look into it on your cars or have you just been living with it (as I have)?

 

Before you spend a fortune at the menders, check your battery posts, make sure the connection is tight on both terminals.. Loose terminals on the battery will cause the car to do all kinds of weird stuff, ask me how i know ")

 

Definately check your vacuum lines. I don't think carbon buildup is a big problem on the r53, but that could be a thing causing it.

 

I wanted to "close the loop" on this thread as I appear to have mostly solved the problem...

So I installed new spark plugs and a new ignition coil. These were both OEM and had 92k on them, so it was definitely time. Upon doing that I of course saw that the #3 contact was heavily rusted, and all of the other contacts also had some degree of rusting (~50%).

After switching these out the car no longer acts as if it is about to stall on occasion. RPM at idle is ~950RPM. I mentioned it was mostly fixed as there is still a slight audible variation in RPM, but it's on the order of 25-50RPM - i.e. I don't see the needle move but can hear the change. I haven't graphed this up via OBDII yet. Right now, I'm putting this variability down as normal behavior... it's certainly not varying enough to be annoying/problematic.

Anyway, wanted to put my solution out there for those that may be experiencing similar issues. Appreciate all your advice and help.