03 MCs R53,
Mods are in the sig, but this problem occured before the mods

Driving the car, no problems, doesn't feel loss of power at all,

At idle, most of the time, car idles perfect!

It could sit and idle for 20 mins with no problems, but every once and a while, it will idle very rough. It lopes like it has a cam in it, and i can tell its missing somewhere.

Its extremely random, it could happen at a stoplight, or it may not happen for 2-3 days.

Any ideas? Just changed spark plugs, and it has done it once still, wires are decently new!

 

nothin?

 

Sorry I can't see the Sig, on the mobile app, did you check the coil pack condition?

 

Its an R53 thing. Happens to almost all of them I have ever driven / worked on.

 

Check for corrosion on cylinder 3 coil terminal as well as the others. This is a common problem.

 

think its losing performance from this. and sig is this:
'03 British Racing Green MCS
Custom Intake
19% Pulley
Detroit Tuned BPV
Soon to be Tein Lowering Springs(here, not installed), Custom Tune(scheduled), Forged Intercooler, Exhaust

 

Happens to me too at random. From what I understand it's a normal r53 thing. Happens in my friends r53 also

 

never dies though. just sounds like it will

 

That's common as what Professor said. So w/ corrosion on 3, cleaning doesn't seem to make much difference from experience but theoretically, it's best to have optimal contact.

 

While the coil contacts, plugs & wires need to be good, since it's not happening all the time, don't know if that would be the cause.

Just curious, have you had many big fluxuations in outside temps since this started? Off the top of my head, seems like the ecu is trying to adapt to a change of some kind and O2 sensors & some others will sometimes be effected by big ups-n-downs in humidity & temps. Not a big deal if this were it, the ECU would then just re-adapt when the signal from those sensors went back to normal.

Again, just a thought, I know my car will idle differently coming down from a hard pull compared to an easy drive, in some different weather conditions, and thats all because of readings from the O2 sensors.

 

no. temps have slowly dropped. and i have *reflashed* the ecu, to relearn my mods. test mode, 19, 21. but it didn't help the rough idle.

 

Like a couple others have mentioned - this can be considered to be a R53 quirk. Mine has done this for as long as I can remember. There's no rhyme or reason for when it decides to start chugging...but in all these years I've never had it stall, and it always clears itself within 5-10 seconds. A quick blip of the throttle will also get it to stop doing this.

So far - mine has done it on cold and warm days, A/C on or off. It seems to be more likely to do this if the engine is fully warmed up and I let it idle for a few minutes (like sitting in a drive-thru or stop light).

There have been reports where having the dealer flash the ECU to the latest revision fixed this problem...but I have also read just as many reports where a dealer re-flash didn't do anything to fix this problem.

After checking the various components (and replacing a few, like the spark plugs and wires) on my car, I've given up on solving this quirk. My money and time can be better utilized on performance upgrades.

 

i agree, not to long ago, i gave up on the problem and have actually learned to kinda like it. my friends and i will joke that it is a large *cam*!! haha!