After getting a PM from W1234 this morning about a rough idle, I thought I would share this in the Knowledgebase.
Just to let you know, I deserve no credit for the write up below (it is essentially copied and pasted with a bit of tweaking to make it read better, simply as you cannot view my other forum without registering).
After reading it a while back, I made a mental note of the problem, and it would be a shame to not offer this information up for all my fellow S50 brothers and sisters
It's such a valuable check and could potentially save a lot of head scratching and wasted garage diagnosis money.
Rough Idling S50
Ever since taking the M3 to Elvington last year, I've been having major idle problems. From hot and cold it was running very rough, and was stalling constantly.
A diagnostic at BMW came up with faulty lambda sensors. After changing these, the stalling went away and the idling improved, but it was still not right. A few squirts of carb cleaner around the airbox told us that there was an air leak somewhere, locating exactly where though was proving difficult.
After doing a quick search of the forum I came across a problem which is simply caused by a small runner T-Piece that is missing.
I couldn't see the t-piece or the cap that should have been present, so decided to strip down the airbox to find out if that cap had popped off on mine:
Low and behold, the same cap was missing on my car, just as in the other thread.
The T-piece on which the cap should sit:
So it was a trip to the dealers to order the cap. Outrageously, the price had gone up by 5p While I was there, I decided to order a new coolant temperature sensor and new O-rings for the airbox. Here's the cap in question:
Fitted:
Although it just pops on, I put a cable tie on it to make sure it won't pop off easily again in the future. I fitted the O-rings, cleaned the ICV and fitted the coolant temp sensor. With the airbox out, it would be rude not the give the throttle bodies a good clean:
Put it all together and fired her up. The result
Idle is now rock steady at about 800rpm. Took the car for a blast to get it up to full temperature and it was perfect. In fact, the car never idled better than it is. I started it from cold again the next day... Still perfect. Job done.
So if your S50 is running a bit rough, have a quick look for this cap. I can see it easily enough as i've got a DaveF kit, but I doubt you'll be able to see it with a standard airbox. But if you remove just the airbox you should be able to see the t-piece.
So there you have it. Please excuse the fact I had to recreate someone else's thread here, but I hope this useful little gem of a check will help out others in the future
Just to let you know, I deserve no credit for the write up below (it is essentially copied and pasted with a bit of tweaking to make it read better, simply as you cannot view my other forum without registering).
After reading it a while back, I made a mental note of the problem, and it would be a shame to not offer this information up for all my fellow S50 brothers and sisters
It's such a valuable check and could potentially save a lot of head scratching and wasted garage diagnosis money.
Rough Idling S50
Ever since taking the M3 to Elvington last year, I've been having major idle problems. From hot and cold it was running very rough, and was stalling constantly.
A diagnostic at BMW came up with faulty lambda sensors. After changing these, the stalling went away and the idling improved, but it was still not right. A few squirts of carb cleaner around the airbox told us that there was an air leak somewhere, locating exactly where though was proving difficult.
After doing a quick search of the forum I came across a problem which is simply caused by a small runner T-Piece that is missing.
I couldn't see the t-piece or the cap that should have been present, so decided to strip down the airbox to find out if that cap had popped off on mine:
Low and behold, the same cap was missing on my car, just as in the other thread.
The T-piece on which the cap should sit:
So it was a trip to the dealers to order the cap. Outrageously, the price had gone up by 5p While I was there, I decided to order a new coolant temperature sensor and new O-rings for the airbox. Here's the cap in question:
Fitted:
Although it just pops on, I put a cable tie on it to make sure it won't pop off easily again in the future. I fitted the O-rings, cleaned the ICV and fitted the coolant temp sensor. With the airbox out, it would be rude not the give the throttle bodies a good clean:
Put it all together and fired her up. The result
Idle is now rock steady at about 800rpm. Took the car for a blast to get it up to full temperature and it was perfect. In fact, the car never idled better than it is. I started it from cold again the next day... Still perfect. Job done.
So if your S50 is running a bit rough, have a quick look for this cap. I can see it easily enough as i've got a DaveF kit, but I doubt you'll be able to see it with a standard airbox. But if you remove just the airbox you should be able to see the t-piece.
So there you have it. Please excuse the fact I had to recreate someone else's thread here, but I hope this useful little gem of a check will help out others in the future
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