Hi, has anyone have engine idle RPM fluctuation problem on '07 MCS? In my car, most of the time it is stable, but sometimes it just keeps bouncing +/-50rpm. Occasionally, it even goes down about 150-200rpm and suddenly bounces back along with ECU throttle control (I heard something like computer applying throttle by itself)

My engine light went on before, and during the time my engine light was on, my idle RPM fluctuated even more. If I applied and let go the throttle, the RPM didn't settle nicely, either. The dealer diagnosed it and found a hose was lose and went sealing it. Now the RPM settles nicely when I apply and let go the throttle, but the idle RPM fluctuation phenomenon still exists even though the amplitude becomes less.

Currently this doesn't affect my driving, but I'd like to know that whether I should keep worrying about this and whether there's anybody has similar issue as that I have.

Thanks,

Jack

 

Is your MINI a hardtop or a convertible? If it's a hardtop, your post belongs in the 2nd-gen forum, not the 1st-gen. I'd just like to see you get the best possible answers.

I wouldn't sweat a 50-RPM variance, if that's all that you're seeing now that the dealer has fixed the leaking hose. Mine's not always rock-steady either, although I'll have to check and see how much of a variance I'm actually getting.

Although, I have a first-gen car, so if yours is a second-gen, we have two completely-different engines, so my data/experience will be useless to you.

 

Thanks, Scott. My mini is indeed the 2nd-gen MCS, and I'm sorry that I posted my problem in the wrong place. Let me re-post it in the other forum. I drove the 1st-gen MC for more than a month before, and the engine idle RPM is higher and very stable, that's why I am kind of worried about my idle RPM. They are two completely different engines, but I still appreciate your opinion.

Jack

 

Two threads (identical) were merged and one post deleted since it was identical.

When you post in the wrong area you can ask to have the thread moved to the correct area. Guidelines direct members to post once in the most appropriate location. We will be glad to help you correct any problems should one occur.

Engine idle fluctuation is common- I have an R53 that has a rough but it doesn't happen all the time. I even have the RMW tune but it doesn't help the idle roughness.

Check your PCV hose (that is it not collapsing) and valve if needed.
Use Top tier gas.
Make sure your spark plug wires are all in good condition.
Run a fuel injector cleaning product like BG 44K Power Enhancer
http://www.bgprod.com/products/fuelair.html

 

Thanks, minihune.

I think the dealer has checked my PCV hose, but maybe not valves. I've been using Top tier gas, but do you have any information about whose gas is the most recommended one?

As for the BG 44K, it really looks like a good thing to try, even my engine is still new (I bought the car on 12/18 '07, and had 3000 miles on the engine.).

 

and one that isn't constant. Fast RPM variation is done via timing, and slow via the throttle body (at least in the R53). I'd expect the same to be in the R56 S, and some variation using valve lift in the R56 Cooper.

Matt

 

I have the same problem in an 04 R53. Once in a while it will drop 200 RPM or so and get rough almost like it has dropped a cylinder. A blip of the throttle and it settles back down.

 

This is a major clue. Let the dealer hook it up to thier machines and figure out why the light went on. It seems to be related.

 

Thanks for you guys' comments.

I'll have it checked again in dealer about three weeks later since the dealer is 70 miles away (Austin Tx -> San Antonio Tx), and I'll keep everyone updated.