99 Porsche boxster unstable idle! revs up constantly maf related?

[randy_k]

Originally Posted by bala

Randy,
that was snug. I just pulled the oil fill tubes, the ribbed one had cracks at 3 places. Of course I broke the one to the engine as well. The plastic must be the lowest quality ever. Anyway, I'd rather replace the whole line as well as the parts for the secondary air system and be done with it. Let's see how those fare.

Gotchca, Good luck. Hope that fixes it for you.
Randy

[mr.datskiy]

I'm gonna check for vacuum leaks tomorrow..

Just the thing is when I unplug maf sensor car changes completely. Don't do that funny rev thing at all. Sits down low like its suppose to be. Driving me nuts!
Could it be that oem maf sensor that I bought is bad?

Or could a vacuum leak cause same symptoms? :/

[mikefocke]

When the MAF is disconnected, the ECU drops back to a basic program and doesn't try to measure anything. Could you have installed the wrong part? Did it have exactly the same part number stenciled on it as the one that was removed? Is it one that requires the ECU flash update? Could you have bought a bad MAF?

[mr.datskiy]

When the MAF is disconnected, the ECU drops back to a basic program and doesn't try to measure anything. Could you have installed the wrong part? Did it have exactly the same part number stenciled on it as the one that was removed? Is it one that requires the ECU flash update? Could you have bought a bad MAF?

Yes same part and numbers matched.. I found a thread about Wayne's maf talk so I was sure to buy the right one.

Just for the heck of it, I'm gonna go get another maf sensor since it came with a 6 month warranty and see what happens. If the same thing happens than I'll be looking for vacuum leaks or whatever but might as well take advantage of that warranty.

[mr.datskiy]

Tried putting in another maf sensor in today. Reset computer and same stuff.

Gonna keep trying things out if you guys have any ideas drop me a line!

[mr.datskiy]

Went and checked for vacuum leaks with a smoke machine at a friends shop.

Turns out eveything good didnt notice any leaks.

He told me to check out idle control valve, would my 99 have that? Where would it be?

Any help is great. Thanks!

[randy_k]

Here's the part and a diagram of where it is. Click on link below.

Randy

Pelican Parts - Product Information: 996-606-160-01-M14

[mr.datskiy]

Originally Posted by randy_k

Here's the part and a diagram of where it is. Click on link below.

Randy

Pelican Parts - Product Information: 996-606-160-01-M14

Finally got the car back up and running mint

It was my dirty throttle body/idle control valve.. Gave that a good cleaning and its running good. Hunting idle is gone!! kinda weird on cold starts but thats fine.

Took me a while because due to my tpc supercharger kit my throttle isnt where a stock boxster one would.

Anyways, Thanks for you help guys!

[oboxster]

Just want to chime in and thank mr.datskiy for his dogged persistence in figuring out the solution to this problem.

Our 1998 986 (115k) started doing the exact same thing - revving between about 1200 to 2000. I pulled off the throttle body and detached the idle control valve, then cleaned both as thoroughly as I could with CNC MAF cleaner. Voila - all good again!

During the test drive afterward the car had one episode where the RPMs dropped very slowly from 3000 back to idle, and then at a stop the idle started bouncing again, this time from about 700 to 1200. I gave it a big rev and it went back to normal. After another 100 miles or so - stop&go and freeway driving - it's still working great.

Big thanks to Black Forest Auto here in San Diego for parts and advice.

Now to get through the smog check in a couple of weeks....