I made this discovery while tinkering with my intercooler fan project. I was sitting at a drive-thru when my idle did its wonderful "ba-dump-ba-dump-ba-dump" routine. Out of curiosity, I push the button to run the blower which sucks the hot air out of the intercooler/engine area...after about 20 seconds of the blower running, guess what? The rough idle stopped!

Then I got to thinking...I realized that I could never remember my radiator fan ever running after a hard drive! Never! As a matter of fact, it never runs when the car is on! To confirm this, I went home and stuck a piece of scotch tape onto one of the fan blades and attached the other end to the fan shroud. I'll be damned. After a short drive, the fan never moved!

Now, thinking back to conversations regarding the ECU and fuel management issues, doesn't the computer dump extra fuel for cooling when the engine/IAT peaks? Well, duh. If the engine is sitting there baking, why would it not dump fuel to cool it? When the rough idle occurs, the exhaust is black (rich) especially when you blip the throttle to clear it. At idle rpm, the engine is not sucking in enough air for the extra fuel, therefore it coughs and sputters. This event would not trigger a code, because it is a "normal" engine function...or so it thinks.

Now, to go even further, if I'm not mistaken most of the cars with the rough idle also have the "cold start" issue. Correct? Well, if the car is shut off "hot", then wouldn't there be the potential for the fuel in the fuel rail to vaporize?? Kinda like the old vapor lock issues of yesteryear. That would explain the car not starting on the first try...no? I am so sure that there is a link here. Last night, hours after the car had cooled, I went back out to my car with a flashlight to have a look at wiring connections to the fan. In the process, I ran the car for 30 seconds or so...not nearly enough to warm up the engine. Then I shut it down...This morning it started right up on the first try! It never does! To me, this means that "cold" fuel was pushed through the system, and was left "primed" for the next start without risk of it vaporizing from a hot shut-down.

So, CHECK YOUR RADIATOR FANS! Please let me know if your fan works.

Does this make sense?

 

My fan definitely works and my MINI also starts on the first try. The problem I have is that right after the cold start, the engine doesn't "idle up" to warm itself and it starts sputtering. Also, the first time I let out on the clutch, the revs will drop quickly like the engine's not getting enough gas. After that, it's fine. It seems like we have to completely seperate issues

 

Kapps, you do have a seperate issue than most of us with the "rough idle" issue. Most people are experiencing the rough idle "at a stop light", or "in a drive-thru", etc. (which indicates it is probably temp related).

 

UPDATE: After letting my car idle for 45+ minutes, the fan never moved. I marked it's position again this morning, and went into my office as it ran. Not a single rotation.


BUT, I went through and checked all the fuses and connections as the car ran. As I wiggled the connection and wiring harness above the throttle body...."WWWHHIIIIIIRRRR". IT STARTED! This was the first time I have ever heard or seen the fan work! I have spent hours under the hood of this car (engine on and off) and never did the fan spin. I feel like an idiot now, because it came to my attention several times in the past, but I never thought much of it.

I cannot get out to romp the car and get the temps up right now...after work will be the real test of the idle issue.

 

I too have the rough idle problem off/on when sitting at stop lights. The car will feel like it's going to stall and my Vac. gauge will drop to about 12 (Normal idle is about 17-18 w/o the AC running) If I let it run for about another 20-30 sec. or tap the gas, it seems to go away. My radiator fan seems ok as I've heard it come on a few times (Usually, after the car is off.)

 

Another thing that triggers the fan is the air conditioner. When sitting still it doesn't take but just a couple minutes at most of idling for it to come on when it's hot outside, even with a cool engine.

 

Day 2: No rough idle last night or today. The car started on the first try again this morning...:smile: Maybe I found something.

 

That's interesting as I do have the cold start problem as well. I do hear my fan run when it gets hot and the engine is running but I've never heard it after the car has shut down. The interesting part is what you said about vapor lock of yesteryear. It's not yesteryear for me. If I shut down the car when it is hot, I can try to restart it within 5 to 10 minutes and it will not start on the first try. Only the second try, the same as the cold start issue but it only occurs when the car is warmed up and the temperature outside is above 65 degrees.

 

Bisch -

This is very interesting info - like some of the other responders, I've hardly ever heard/seen the fan running on my car with the exception of when the A/C is on -- I've *NEVER* had it run after the car is turned off. I always wondered about that, since there is a warning label by the fan shroud talking about the fan running at any time. Even in hot, sweaty St. Louis.

Can you take a picture of the connectors you're talking about that you suspect?

Do we know for certain that the fan should come on without the A/C running or after the car has been turned off?

 

My fan never runs with the A/C off until the ECT gets to 222F. With the A/C on, I believe it kicks on at 180F or so.

 

The fan will definately come on when the car is off. I have heard mine.
In fact this weekend on a M2C2 Mini Rally in the mountains, we stopped at an overlook after a long run. Nearly all the MINI's fans started... like they were singing to us.

 

I have heard the fan running at the moment I shut the car off, and the fan stopped when the key was turned off. I guess it's possible that the A/C was on and the temperature was between 180F and 222F -

 

Same thing this weekend at the autocross I was at. As we were lining back up, all of the Minis had their fans running some with, some without the car running.

 

The engine is starving for two things:

COOLER AIR!

The ECU software has trouble overcompensating for the high engine bay temperatures, so the program is supposed to rise the idle to around 1,000 RPM when stopped. This problem is evident in hot, humid climates and when the A/C is running.

The engine in these cars is usually starving for a gasp of air and the controlling software sometines doesn't know what do given the reduced intake air and higher temperatures.

 

My MCS's been doing this lately too, darkfact. I'm taking it in to try & find the problem for the second time. What's the Vac gauge? I have only a tach. My radiator fan has come on before (usually hear it as I'm walking away), but I haven't heard it lately come to think of it and it's been really hot here. The temp gauge is spot on though. My friend thought I might have an outside air leak as they found a loose hose last time I tried to have it fixed and replaced it. I tried his suggestion of misting around the engine, but it didn't reproduce it. It's been worse for me since the hose replacement.

Where would I check the fan connections?

 

[QUOTE=BigBrownDog]

Can you take a picture of the connectors you're talking about that you suspect?

QUOTE]

In this picture, the connector is at the bottom of the pic, directly below the throttle body.

My son was showing me how to fix my car...

 

[QUOTE=Bisch]
My son was showing me how to fix my car...
QUOTE]


The MINI Mechanic

 

The boost/vac. gauge is actually an aftermarket gauge I put on. It's nice because it shows vacuum reading plus boost pressure off the supercharger. The rough idle is most likely an ECU program bug. I've read that some people say the new ECU V38 helps w/ the idle problem and some say not? Ive been meaning to call the MINI service dept. here and just ask. It hasn't really been a problem for me, just kind of a minor oddity. Probably the easiest thing to check for your fan is the fuse box to make sure it isn't blown. However, it rarely seems to come on for me unless I've been using the AC.

 

Bisch, thank you for the post. I'm going to have a window repaired and will discuss this very topic with the service advisor. I just thought I was doing something to cause this to happen all the time. It's good to see it happens to others.

Thanks again! :smile:

 

Bisch, I also have the cold start and I sputter at idle. I am going to Peabody sometime next week for my 25k/30k service. I will see what they say and maybe mention what you have.

 

bump.
I've heard a few questions regarding this recently, and the idle has become a bit of worry to me, also realized I've never heard the coolong fan so I'll have to go out and give this a try.

 

I have a cooling fan!!!!!!!!! Tonight was the first time I've ever heard it in almost seven months of motoring, and as best I can tell the idle seems smooth certainly didn't harm anything.

 

My 02 R50 had rough idle for years. I thought it was simply a characteristic of the first gens. I have a new fan assembly, all the speeds work with the functioning resistor. I replaced my fuel filter. I have new injectors and a facelift fuel rail.

My rough idle was solved by replacing both cam and crank position sensors. Both are Dorman aftermarket. The cam sensor in particular really smoothed the start and when decelerating to zero at a stoplight. No more stumbles.

I also have a new battery and reasonably new Valeo alternator. All being parts to look at replacing it worn.

 

Just:

Why did you replace your cam sensor? Did it throw a code?

My car has a very rough idle but has zero error codes. I bought the Foxwell scanner with BMW/Mini software which is very detailed but it found nothing.

I’ve already thrown a bunch of money at this problem so a cam sensor isn’t my first mistake but it would be nice to hear that you didn’t have codes.

Peter