Idle Problem mystery?

[IMACMAN]

Hi... I've been searching for the solution or problem but no luck. About a week ago... my 99' 986 ( 5 Sp Standard Trans ) out of the blue started to have and Idling problem... when the transmission is not engaged ie... either in neutral or with clutch depressed the engine idle drops below the normal ( say 800 rpm ) to below 600... which seems as though the engine is about to stall.... ( it hasn't actually stalled yet )...but then it recovers somewhat... but then does the same thing again? I found a post on another site.. that describes the issue exactly...unfortunately there was no solution or explanation here is what I read......


( The engine speed will droop well below the intended 800 RPM after depressing the clutch when returning to idle. The speed will droop as low as 600 RPM, at which point the engine starts to stumble and die before recovering and overshooting to 1000 RPM and then returning to the standard 800 RPM idle speed. This problem happens almost every time the car returns to idle, to varying degrees, )...


I'm new on this forum so I'm not sure if it is ok for me to post a link to the site... I'd like to post the link as it goes into exactly what this person tried to find out what the problem was.... including what some mechanics & Porsche dealers had to say... but no solution yet.

Not to complicate matters...as it may just be a coincidence....but... the problem started happening.... just after i had purchased a WIFI OBD2 unit, and bought both the REV and FUZZYCAR apps for My Ipad. both of the Apps worked... and are pretty neat....so it has me wondering if I caused this...or if it.s just a coincidence?.. Any help is greatly appreciated...

ONE LAST Issue... I'm not sure how to set notifications to let me know if /when I get a response to this post? I will check back to see if there is a reply... but email notification would save me alot of log ons. ( Also not sure if I'm psoting in the right place?.. Apologies if I'm not )

Thanks

Imac

NL, Canada

[san rensho]

CEL? If so what are the codes.

I would start with cleaning the throttle body and idle control valve.

Then check for a vacuum leak.

[Mrmaddbrad]

If there is no CEL, you don't have an air leak. The WIFI OBD2 is just a coincidence :P

However; It sounds to me like a MAF Sensor. These seem to fail quite a bit in boxsters, especially the pre-2000 models.

There are quite a few things it could be. But if the idle seems to hunt as you describe and occasionally find it's "proper" idle, then i would mostly likely assume it was a MAF sensor; especially without previous knowledge of the car.

Best of Luck!
~Brad

[thstone]

Esay to check if the MAF is good or bad. Disconnect the wire harness that connects to the MAF and then start the car and see if the car idles better (normally). If so, then the MAF is bad and needs to be replaced. If not, then its something else.

And don't worry, you won't harm the engine by running the car for a short time without the MAF.

[IMACMAN]

Thanks guys..... No there is no CEL or other lights ( They do all work )... the car is a 99 with 69k on it... a recent purchase in April... I've put about 1900 miles on... ( couldn't help it I love the thing...lol ) the engine runs very clean and strong all the we through the tach in every gear ( Theres' not alot of "gear time" in first )... at about 4000RPM mark the sound changes ( power band area I guess ) and it really takes off... sounds like a jet...lol...or formula 1 car.... sounds great, no sputters or hesitation. I've had the car on the highway..... but still have not had it in 5th gear yet...lol... true!!!

I had a porsche mechanic ( independant ) do the alternator, Brakes, Tires, Oil change and filter and front wheel bearings on front ( there was a small rumble in the front ) the bearings smoothed that out. He had the car up on the lift and told me the car was in great shape... very nice... so that was a relief : ) Then this started : (

I should mention the OBD2 worked great, no error codes etc... and the REV app lets you see all of the sensor data...so maybe the MAF data issue is showing there?... I wouldn't know what to look for or what the data and graphs mean... but I do know it's in real time as the car is running. It's in getting a Full detail Job on it now... then off to the Porsche God up here on the rock.

Some days the car ( Ride wise ) is amazingly smooth over the bumps etc... then the next day..... theres... a fair amount of banging over the bumps in the back?.. strange... I'm having him the Mechanic see if he can locate the banging... I do know one of the plastic wheel gaurds ahead of the rear wheels is a bit loose, and one of the small metal shields ( ? triangke shape 12" or so across ) is missing s screw and moves up & down an inch or so. Thanks for checking this thread... any help and advise is appreciated... this forum is a god send....it's already answered and solved several issues for me... and having some knowledge and understanding of the car helps alot when I'm talking to the mechanic about it. : )

[bar10dah]

[QUOTE=IMACMAN;293123]No there is no CEL or other lights QUOTE]

You can still have what's called "pending" codes and not have a CEL. Buy (or borrow) a code reader that also checks for pending codes. Better yet, buy a Durametric. But if you can't spring for the $287 Durametric right now, at least get your car checked for pending codes.

[IMACMAN]

Hi Bar, thanks for the reply, I just checked the REV app, and the app says it is capable of displaying pending codes..... when I first hooked the App up to each of my cars, the Porsche, and the Nissan were clear of codes and pending codes... but the Grand Prix did show a brief code when I started the app.... then it disappeared.... it turns out that the Grand Prix oil level was low, and the onboard computer showed me that condition as well...so I topped up the oil in the Grand Prix, and the code ( which I think was related to that, on the REV app, cleared it self, after I manually cleared the message on the Car's Unit ). The reason I mention this is that the REV app appears to include Pending Codes.... but who knows..... it was a $40 app...lol.... I'm going to bring the app up to the Porsche mechanic and let him have a look and tell me if it's worth bothering with.... or if I just have a cool looking set of redundant digital displays...lol... Where can I find the Durametric? I'd love to have one..... INMHO the other apps I have aren't going to be of any diagnostic value... If I'm uncertain of whether or not they actaully doing what they say they can do...and the only way to find that out, would be to test them side by side with a durametric unit that you mention.

Thanks

IMACMAN




Imacman

[san rensho]

Originally Posted by Mrmaddbrad

If there is no CEL, you don't have an air leak. The WIFI OBD2 is just a coincidence :P

However; It sounds to me like a MAF Sensor. These seem to fail quite a bit in boxsters, especially the pre-2000 models.

There are quite a few things it could be. But if the idle seems to hunt as you describe and occasionally find it's "proper" idle, then i would mostly likely assume it was a MAF sensor; especially without previous knowledge of the car.

Best of Luck!
~Brad

You can have a vacuum leak and no CEL. Take off the oil filler cap while the car is running, you now have a vacuum leak, but it will not throw a code.

[bar10dah]

Originally Posted by IMACMAN

Where can I find the Durametric?

Pelican Parts - Product Information: DURA-ENTH-1