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Old 07-01-2011, 06:44 AM   #1
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Slightly rough idle. Help?

A month ago I was getting 1128 and 1130 codes so I replaced the MAF.

Two weeks ago I was getting smoke on start-up so I replaced the AOS. No more smoke.

Now the Boxster has:

1. A rough idle. When stopped, the rpms go back and forth from about 600-800.

2. I have a slight loss of engine power and a high pitched whine (not very loud at all) when the engine is cold. This issue goes away when the car is driven for a few minutes.

3. The car has a tiny bit of trouble starting sometimes. Just barely, but you can tell something isn't right.

I cleared the codes this morning after I replaced the AOS. Now I have to wait for some codes to appear so I can see what is wrong.



Any ideas?

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Old 07-01-2011, 07:00 AM   #2
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From the research I have done, my thoughts are that there is a leak in the air/oil bellow. But that part comes with a new air/oil separator, which I just replaced.

I think the high pitched whine is an air leak, but I'm not sure where it's located.
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Old 07-01-2011, 07:15 AM   #3
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I've read on this forum and elsewhere many times about cracked or leaking oil fill tubes. I don't remember the exact problems this causes but it may be worth doing a search and seeing what you find.

When I replaced my MAF I remember having a hunting idle for a bit, but it eventually started running normally. Since you replaced yours a month ago I'm sure that is long enough for that to have cleared up if indeed that was the problem.

What year is your car and how many miles?
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Old 07-01-2011, 07:28 AM   #4
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I'll do some research on leaking oil fill tubes, thanks.


2001 Boxster S, 80k miles
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Old 07-01-2011, 10:26 AM   #5
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Similar Problem

Not to hijack the post, I just didn't want to start a new thread, but I have similar problem.

This is my first Boxster, I had it for about 8 months now.
I had the oil changed at the dealership not long ago (400 miles since the change), but about a week ago I noticed a short puff of blue smoke on a cold start. It's been doing that now at every cold start for about 5 seconds.

As soon as I saw the smoke I checked the oil level and it was more than the norm. I drained about 3/4 of a quart before reaching the optimum oil level. Besides that, while I was at a stop light the car felt rough on idle just like Highlow described 1... " the rpms go back and forth from about 600-800". And I've also experienced 3. with the troubled start.

My Boxster has 63k miles on it, at 62k+ I've changed the air filter, fuel filter, spark plugs, and cleaned the maf sensor + oil change/filter at the dealership. The throttle is really smooth and the car feels great, but that rough idling freaks me out.

From what I've read here on the forum and on the net, I might as well change the AOS.

But could the oil overfill have something to do with it? I will have a talk with the service manager at the dealership..
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Old 07-01-2011, 11:49 AM   #6
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Before you talk to the service manager about the oil overflow check it again.

When my car is cold, the oil meter reads at the very top, but when the car is warmed up, the oil meter reads right in the middle of the two lines.
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Old 07-01-2011, 02:24 PM   #7
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Quote:
Originally Posted by Highlow (Robo-Top)
A month ago I was getting 1128 and 1130 codes so I replaced the MAF.

Two weeks ago I was getting smoke on start-up so I replaced the AOS. No more smoke.

Now the Boxster has:

1. A rough idle. When stopped, the rpms go back and forth from about 600-800.

2. I have a slight loss of engine power and a high pitched whine (not very loud at all) when the engine is cold. This issue goes away when the car is driven for a few minutes.

3. The car has a tiny bit of trouble starting sometimes. Just barely, but you can tell something isn't right.

I cleared the codes this morning after I replaced the AOS. Now I have to wait for some codes to appear so I can see what is wrong.



Any ideas?
The high pitched whine is probably your Secondary Air Injection system, the pump runs for a few minutes when the motor is cold.

As for the rough idle you might have a vacuum leak (should get a trouble code of some kind). If you don't get a trouble code after a couple hundred miles I recommend cleaning the injectors and induction system, I have done this a couple times (same issue you are having). The pro shops can do this or you can purchase the cleaning systems [url]http://www.bgprod.com/products/products.html[url].
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Old 04-03-2014, 02:31 AM   #8
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I know this is an old thread but I'm having the same issue and was hoping to find a solution. My rpm drops by about 50-100 rpm continuously causing the engine to shake. I replaced the aos, maf, oil fill tube, and cleaned the throttle body. What else could it be.
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Old 07-01-2016, 01:46 PM   #9
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I know this is an old thread but just in case someone comes wandering in looking for a solution. I had the same issues with my '01 Box. My mechanic ran all the tests on it and said everything looked fine with AOS and was sure that the throttle body was causing the problem. He told me to clean it and sure enough, that solved the problem. All that carbon build up was causing the rough idle. This is a fairly easy repair, although taking off the intake box was a pain in the arse. Here's the link to the repair - Porsche Boxster Starter Replacement - 986 / 987 (1997-08) - Pelican Parts Technical Article
I know it says it's for the starter replacement but the very first part shows you how to remove the throttle body.

Hints**
You don't need to take off the hose that goes to the AOS to take the throttle body off.
You'll need a torx set to take the 4 long gold colored bolts that connect to the intake tube just behind the throttle body. (See picture in link below.)
http://www.pelicanparts.com/techarticles/Boxster_Tech/83-ELEC-Starter_Replacement/images_med/Pic2.jpg
You will need to disconnect some electrical plug on the bottom of the throttle body.
That's it!

Good luck!

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Last edited by impboy; 07-01-2016 at 01:54 PM. Reason: Added more information.
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