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Old 10-19-2011, 04:44 PM   #1
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What is wrong with it?

No CEL.
For the past year, I have been driving with idle jumping up and down.

I hear the sound of vacuum leak. I hear a blow or air every time the idle jumps every 1.5 seconds.

Mechanic insisted that it is not a vacuum leak. He told me it feels and sounds like it was running rich and that the MAF sensor was not being accurate. He just did the WD40 spray test all around the engine and hoses to make sure.

He recommended replacing the MAF sensor. Does everyone here agree? Remember, no CEL. I double checked for hidden codes by plugging it in scanner.

Also, there are two different part numbers for MAF sensor for the 2000 986 2.7L. I asked this question before, but got no responses. It is a 2000 model, but was manufactured in late 99. What is the right part number? The Price is $50 + difference between the two.
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Old 10-19-2011, 06:46 PM   #2
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Just remove the existing one and check for sure...the last 2 numbers may be lower then the most recent revision. I also just call my parts guy at Porsche and give him a vin...usually they can tell you what you'll need.
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Old 10-19-2011, 08:12 PM   #3
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I'd be inclined to ask the mechanic check the idle control valve before replacing the MAF. Could be either component.
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Old 10-19-2011, 09:50 PM   #4
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This is just my own experience. Had the same hunting idle problem. Even after the complete 90K service at the independent, it still did it. Two years later the MAF kept giving me CEL's, so I replaced it. Now, no more hunting idle.
The easiest way to tell what MAF you have is to pull the old one and read the part # off of it like WhipE350 says.
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Old 10-20-2011, 05:34 AM   #5
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Thanks guys. I will try to find a torx set so I can get the old MAF sensor out to read the part number.
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Old 10-20-2011, 05:40 AM   #6
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O Reilly sells a "security" bit set that includes the one you need plus a bunch more and it only costs about $5. I had to replace the MAF in my car too and it made a difference but if you hear a vacuum leak (hissing) then you probably do have a leak despite what your mechanic says. Wiggle the oil fill tube back near the rear bulkhead. If you hear a change you might need a new fill tube. They're famous for leaking when they get old.

You could also find somebody to give your car a smoke test to search for vacuum leaks. I found a guy who works generically on foreign cars and they didn't know much about Boxsters but he knew how to hook up the smoke machine and he found 2 leaks.
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Old 10-20-2011, 05:51 AM   #7
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Ughkjsavu. The cheapest smoke test I found so far is $110 at Midas. Other independent shops say that don't have a smoke machine that works on exotics or they say that they don't know how to work on mid-engines. They are just being lazy.

I didn't think a Boxster is considered an exotic, but some mechanics do.

Porsche dealership in my area charges $145 for the test.

I do hear the hissing sound loud and clear. I guess when I get my next paycheck, I will do the smoke test and get a new MAF and plugs at the same time.
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Old 10-20-2011, 08:18 AM   #8
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Security torx bit

FYI, I managed to lose the bit I needed for the MAF. I found that my local Carquest sold indiviual bit (T15) for a couple bucks as opposed to buying a whole set.
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Old 10-20-2011, 09:08 AM   #9
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Do yourself a favor and remove those torx screws by whatever means necessary and replace them with a proper phillips head screw so you always have the right tool within arms reach.
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Old 11-03-2011, 07:14 PM   #10
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Update on rough idle problem: I still have it. I cleaned the Idle Control Valve and Throttle Body. Before reinstalling them, I checked again for vacuum leaks since I had better access to the hoses. All hoses are in good condition seem to be aging well.

I know it is not the coils or spark plugs. I know it is not the ICV/Throttle Body. I know it is not a head gasket. Mechanic says it is not a vacuum leak and I could not find a vacuum leak using various methods.

Last possible thing I can think of that causes a rough idle is the MAF sensor, but it still does not make sense because a MAF sensor is supposed to cause a CEL and I do not have a CEL light On. Plus, my scanner says no codes found. Anyways, I will try to clean it and reinstall it when I buy MAF cleaner.

Can you guys think of anything else that causes rough idle?

Last edited by ProjectM96; 11-03-2011 at 07:27 PM.
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Old 11-03-2011, 07:22 PM   #11
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Quote:
Originally Posted by ProjectM96 View Post
Update on rough idle problem: I cleaned the Idle Control Valve and Throttle Body. Before reinstalling them, I checked again for vacuum leaks since I had better access to the hoses. All hoses are in good condition seem to be aging well.

I know it is not the coils or spark plugs. I know it is not the ICV/Throttle Body. I know it is not a head gasket. Mechanic says it is not a vacuum leak and I could not find a vacuum leak using various methods.

Last possible thing I can think of that causes a rough idle is the MAF sensor, but it still does not make sense because a MAF sensor is supposed to cause a CEL and I do not have a CEL light On. Plus, my scanner says no codes found. Anyways, I will try to clean it and reinstall it when I buy MAF cleaner.

Can you guys think of anything else that causes rough idle?
Yes my 2002 had the same problem that you are describing, it turned out to be the idler control. car runs fine now.
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Old 11-05-2011, 10:01 AM   #12
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No more idle problems. For now.

I guess the car needed to be driven. Cleaning the throttle body and ICV seems to have fixed the problem. I still had the problem when I started the car directly after the cleaning was finished. But once I started driving it, the problem went away.
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Old 11-06-2011, 10:33 AM   #13
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If the rough idle returns, you might consider the O2 sensors. I had a similar problem. No MAF or O2 codes, but I replaced MAF first and nothing changed. Then I replaced the O2 sensors car had 90K+ miles and they were getting tired. After driving for a few miles, the idle steadied right up and has been that way ever since.
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