Hi Guys:

Ever since I purchased my 04 MCS (with 19K miles) on occasion she does this sputtering thing at the stop light. The revs go up and down from below 1k to a little above it. Almost to a stall, but it never does. Lately with about 100K miles it seems to do it more frequently. While under warranty I took it to the dealer that suggested that I use a detergent gasoline. Mini apparently had a TSB on this. I searched the threads here and they were old regarding this issue.

Is there a solution for this? Is there a MOD that I can do to stop this annoyance? There seemed to be many people with this issue in the past, but no solution.

Thank you!

 

My 04 S does the same thing, I am a technician and have had access to tsb information and can find nothing that matches. Have had it at the dealer (extended warranty) and they could find nothing and have also asked about it on here and the closest thing we could figure was a weak bypass valve allowing the engine to "undulate". I haven't yet but plan on replacing my bypass valve with a detroit tuned one to hopefully fix this and a little performance gain.

 

If memory serves, the primary issue with variable idle RPMs has to do with the ECU programming. My old '02 MCS had an ECU recall, and the dealership upgraded it in October 2005. I had the idle problem from then on. They claimed they were not authorized to go "backwards" on the programming. Really made me mad.

Have the dealership do a diagnostic to make sure no codes are coming up (even if the engine light is not on). If all checks out, run a bottle STP fuel treatment (or fuel injector cleaner) or a can of Sea Foam through the engine to make sure the the fuel system is clean. If all is OK afterward, it's the ECU programming.

 

My 04 MCS was doing this, although not as badly as described in the OP... I had the car in the shop for other reasons, but had them replace the plugs & wires while it was in for service... The erratic idle stopped after the wires & plugs were replaced...

 

I have had the hunting idle issue on my 2003 MCS since I have owned it, seems to happen alot more in the heat, sounds like someone dropped a huge cam in it

wish there was a solution for it..

 

Mine does it also every once in a while. It does sound like I have a big cam in it so I don't mind it but I would like to find the reason. I have noticed that the vacuum on the boost gauge stays constant when it does do it and I have already done coil, wires, and plug with no avail. I also installed a 2% o/d pulley with no change. Ecu tune didn't stop it either. Last time I had my scangauge connected it did it but I wasn't logging at that time so I couldn't pinpoint anything. Only at idle it does it and when you give it some gas it goes away. Injectors, headers and seafoam didn't stop it. Oh it did do it when I first started my car from cold start on a 70 degree day. All I can say is BP valve, fuel pressure, or ignition timing.

 

If your idle problem is sporatic, it's the "idle" circuit part of the ECU tune. This part of the tune is done at the dealership. Aftermarket tunes usually only affect "wide open throttle" (WOT), which is handled as a separate program in the ECU.

 

same problem..detroit tuned bypass vavle installed and it makes no difference still flutters at idle...had someone at autox meet ask if it was cammed....its not ...looking into new fuel injectors 450cc..and a tune

03 MCS,dt bypass valve,15%pully,screamin demon coilpack,one step colder brisk plugs,custom cherry bomb dual side exit catback

 

First thing I would do is to get the dealer to re-flash it....that way you have the most current tune.....and if the current tune somehow got garbled, getting a custom tune may not fix it. By getting a flash, you will have the most current software.

Also for those folks with low miles, or a car that has done lots of sitting, like the OP, it is VERY possible the fule filter/Fuel lines have some varnish/gunk from fuel that "spoiled" from sitting too long. I would run some cleaner...sea-foam in the gas, maybe fog it too to clean the sensors, then change the fuel filter. the OP having only 19K on an 04' makes it sound like it has sat quite a bit.....

 

i have an aftermarket tune..but it was done when the engine was stock....the flutter isnt bothering me now so once i get injectors and a cam ill do a ecu flash..

 

If you do get it re flashed....you will "loose" the tune...till it gets re-tuned.
One thing....if you have the DT tuned bypass valve, and the vacuum increase mod, both, the results are off....check out how the vac lines are plumbed....and the thread...it might have been done before you got the car...and the combo might be giving you the funny response.

 

im the original owner of the car so no worries there...and id be getting a dyno tuned ecu flash...checking the vacum plumbing on my next day off

 

Thanks everyone for their responses. Yes I do have a custom dynotune on my car. Reflashing the ECU would not be an option. I am also at 100K miles so going to the dealer is probably not an option as well. I am going to contact Jan and see what he can do.

 

Before you go talking to JAN (he might have some basic suggestions) I would check all the basic mantinace items. Like it has been stated previouly, with only 19,000 miles on the car in 7 years or so, many things should be done to keep it running right. Jan is good....but he needs to have all the basics done before he suggests things to look at!! Besides, do the plugs, changing out the fuel filter, and checking the coil for corrosion will give you and your car some "private" time.

 

have you tried cleaning your MAF?

that could help if its dirty

 

'02-06' MCS's don't have a mass airflow sensor. They are set up as speed density, relying on dual manifold absolute pressure (MAP) sensors. The '07 and newer turbo MCS's have a MAF sensor.

 

Sorry for drudging up an older post but my car is now doing the same thing as the OP mentioned above. Has there been a solution? It has really started getting bad the past few days, to the point that the car seems like it is going to die but doesn't. I've changed the plugs, wires, and I'm about to change the coil pack. I don't mind buying parts if it fixes the problem, I just hate throwing parts at it if it doesn't need them.

 

All of the suggestions are good. Check coil (esp #3) and make sure it isn't rusty. If plugs/wires are old, could be time. I wouldn't hesitate to use some carb cleaner down the TB, check all vac hoses, IC boots...there are many things that cause these symptoms and generally starting with easy then moving to hard and expensive is the way to go.

 

Try a new T-Map sensor

 

Hey Blue Agave:

I am the original OP. Did reolacing the T MAP sensor work for you or was that just a guess? Still trying to find a solution.

 

I've changed the spark plugs, plug wires, and cleaned out the throttle body with no change in behavior. What I noticed was the car operates normally initially, once it warms up, it starts misbehaving. Typically it is at its worst when I get off the interstate. Yesterday I changed the coil pack so we'll see if that resolves the issue. The mornings are still cool enough that the underhood temps aren't high enough to trigger the problems.

 

Yes, I replaced my sensor and it did work. In addition to stalling at idle, my engine would stumble at hard throttle and at WOT - large pressure differential between the two sides of the supercharger. My engine threw a code, which clued me into the T-map sensor. I can't recall which code it was. It's a very simple repair. As I recall, the part is approx $80.

 

I guess I'll give that a try. Although for my car, it seems worse when the weather is colder. When leaving the house the car behaves, since the garage temp is typically warmer than ambient. However, leaving work is a different story. Upon exiting the interstate, the car will slam gears (it is an auto) and upon stopping, it will stumble, and lately, die. The strange part of this is, if we shut the car off for 10 minutes or longer, then restart it, it will run fine and not exhibit any issues at all, until the next day.

 

Do you have a scangauge? If not get your car plugged into an OBDII reader. How many miles are on the car?

You may want to check the bottom of your coil pack. If you see white you will know its bad which means your ignition system is compromised causing abnormal idle at times.

Here is an example of a bad coil pack

 

There are almost 114K miles on the car now. As for the coil pack, I've already replaced that, since the symptoms are still apparent, that tells me the original coil pack is probably still good.