Idle issue
 

I've got 2000 Boxster S with the tiptronic. I recently had theAOS fail and I replaced it and it's associated hoses. Of course I had a CEL. Can't find anybody here, Panhandle of Texas, with a compatible code reader. The car was running rough after the AOS was replaced so I replaced the plugs and it helped but didn't clear the CEL even after unhooking the battery. The ideal was rough, fast and fluctuated. What I read on the internet this could be caused by the MAF which I replaced, idle still fluctuated between 900 and about 1500 rpm. The only thing I haven't done is pull the throttle body, clean it and the butterfly. Getting frustrated! Any ideas??

Probably a vacuum leak.
Replacing the AOS in such a cramped location sometimes causes dislodging of vac limes.Some are not put back correctly,the oil filler tube cracks. There re some good Threads on the techniques to locate the leaks.Tedious work with carb cleaner &/or propane &/or smoke machine.

The fluctuating idle just started after replacing the MAF, last week. The AOS was replaced in October. Car ran better and of course no smoke but still had CEL. Was told by a Mechanic I know that the k&n air filter could cause MAF issues, replaced the kn with a new Wix paper filter, cleaned the MAF, car ran great. Still had CEL. Cleaned the MAF several times still had CEL. Replaced the MAF and that when the massive fluctuation in idle speed started. Guess I'm going to have to break down and haul it to the dealer in Albuquerque.

Before you spend money needlessly at the dealer on a simple fix, there are numerous threads here that address rough idle (and most other issues).

You can test for vacuum leaks by using ether (starting fluid in a spray can). Open your engine cover, let the engine idle and spray small amounts of ether near the ends of the vacuum, the intake tubes, MAF and smog hoses and if the idle increases, you have found your leak.

NB. You have to be very careful with the ether, as it is highly flammable.

You may have a crack on the (long) accordion hose that goes from the top of the head (or block?) behind the driver side to the AOS, these get very brittle with age

The AOS hoses were replaced when the AOS was replaced.

Is the MAF the correct part? There were some changes where the ECU had to be flashed if you got the updated part.

Have you driven the car through enough cycles for the ECU to relearn?

How long was the AOS bad and how much damage did the CATs and O2 sensors take?

Have you cleaned the throttle body and air intake of oil from the prior failure?

The MAF was the same as the one I pulled out. I have not cleaned the throttle body and the butterfly. That is my next task. Don't know about damage to the cats and O2 sensors. As soon as the car started to smoke I stopped driving it and ordered the AOS and associated hoses. When I pulled the plugs there was very little oil fouling on them, after I changed the AOS the car ran great, fuel mileage improved bu still had the CEL even after disconnecting the battery, CEL went away but came back after about 20 miles. The fluctuating idle speed didn't start until I changed the MAF. I'm going to pull the MAF again and clean it as well as the TB. We will see how that goes.

You may want to make 100% sure you have the correct MAF. They all look pretty much the same but their sensor characteristics have to be matched to you particular car. The 2000 year is a cross over year.

This is from the Pelican DIY article. Link here Porsche Boxster Mass Air Flow Sensor (MAF) Replacement and Troubleshooting - 986 / 987 (1997-08) - Pelican Parts Technical Article

Porsche Part # BOSCH Part # Application Notes
996.606.123.00 0-280-217-007 1997-99 All Boxsters Sensor for use with cable throttle cars
996.606.124.00 0-280-218-009 Early 2000 Boxster / Boxster S Original sensor for E-gas cars
(thru Boxster 2.7L Chassis #98 6YS 62 0414 and #98 0YU 62 5099)
(thru Boxster S 3.2L Chassis #98 0YS 66 0257 and #98 3YU 66 2413)
986.606.125.00 Mid 2000-04 Boxster / Boxster S First updated sensor for E-gas cars
(discontinued and replaced with version 125.01 below)
986.606.125.01 0-280-218-055 Mid 2000-04 Boxster / Boxster S Latest updated sensor
987.606.125.00 0-280-218-145 2005- All Boxster / Cayman Integrated housing design

Latest, the rapidly fluctuations in idle speed seems to have stopped to some extent. When first starting the car idle will jump to about 1400 rpm and then will fall to around 800. After driving the car to running temp the idle will settle at 1000 rpm, some times but not all the time when I stop the car and put it in park the idle will rapidly increase to 1800 rpm for a few seconds and then drop back to just above 1000. Still have the CEL. What should be the normal idle rpm? Don't remember what it was prior to changing the AOS.......finally got around to pulling the throttle body. It was dirty but not as bad as I thought it would be. After reinstalling CEL went away and idle steadied at 1000. After driving about 50 miles CEL came back and idle returned as mentioned above. I'm at a loss The to how to proceed except to take it to the dealer. Love the car but I'm about ready to find it a new home. Car runs great, fuel mileage is 21-22 mpg.

Before throwing more money at the problem, you need to get the car scanned and find out what the codes are. The only way you are going to succeed without doing this is by pure luck.

Can't find anybody here with a scan tool to get the codes. Is there a throttle position on the 2000 Boxster S and if do where is it located?

AutoZone will scan and provide codes for free...

They didn't have a code reader that would recognize the Boxster.

You can go on Fleabay and get a cheep old version of the durametric software from china and $25 or so and scan it yourself. It will read the codes and clear them and might help you bottom out the issues. DO NOT try to upgrade or use later software as it will kill the cable.