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Porsche 986 2.7 2000 idle issue/hunting

C

Camscott98

New member
Hello, this is my first post in the forum, I am currently at trying to solve the following issue with my Boxster:

From cold: the revs will sit just over 1000 (1100-1250) then after about a minute will drop below to about 750/800 which is normal I think.
At the 750/800 stage the car starts to hunt and run rough at idle approx 500 RPM variance, which feels and sounds like a light misfire. Even when the car is fully warmed up out on a drive sitting at idle this will still occur. Applying the throttle back to the 1100 range will stop the symptoms. No Check engine light or any codes.

so far to try rectify the issue I have:

fitted new spark plugs
cleaned the throttle body (which was dirty)
cleaned the MAF (looked brand new before cleaning) I've unplugged the MAF sensor while running and it made no odds, still rough.
Changed the AOS (Air Oil Separator)
Checked for vacuum leaks (can't find any)


Other than the symptoms at idle the car runs as it should the rest of the drive. Any help would be greatly appreciated thanks.





 
Hi,
I'm no gambing man but I'd say ignition coils.
I changed all 6 on my 2001 Boxter S 986 and the car felt and ran like a new car. Such a difference.
CarParts4Less is a good starting place. Got mine from there. Went with the Beru option.
Good Luck,
Steve

 
Hi Steve,

Thanks for the reply I might give that a go, I was a bit hesitant as in I thought the ignition coils would’ve brought on a CEL however as I’m now running out of options it will be another thing ruled out if nothing else! Thanks , Cameron
 
You should have taken into a specialist and the computer would have solved the problem.

Unfortunately exactly the same thing happened to me on a 2009 car it was bore scoring .


 
Thanks for the replies I’ll also have a look at the throttle position sensor, the car isn't showing any codes as has been plugged into a snap-on diagnostics machine at a local garage. I’ll give fixing It another go tomorrow!
 
Cameron,

I assume that it's an electronic throttle system? It looks as though you've covered most bases so far. If the engine's actually misfiring then I think that changing the ignition coil-packs would be a good idea, but if it's actually hunting then you may need to look elsewhere. When you cleaned the throttle-body, did you make sure that the butterfly movement was really free and it wasn't sticking? Probably best to remove the TB to ensure a thorough clean.

I'm sure that there'll be some sort of idle control valve in the system, but can't help re its location if there is and you want to swap it out.

Jeff


 
Hi Jeff, thanks for the reply,

Its the E-gas version of the 2000, so electronically adjusts, I did a reset procedure - ignition on for 60 sec then in the off position for 10 seconds - no change after this. I currently have the throttle body off after a second doubt about how free it was. The car is only playing up at idle and theres no misfire throughout the rest of the range either however I might just replace the coil packs as a maintenance measure seen as I've already done the plugs. I scouted the internet last night to locate an idle control valve also however it proved difficult to find, i'll search further tonight. Thanks again Cameron
 
Another reasonably common thing that can cause a lumpy idle is a Variocam solenoid. As Gordon says, get a proper diagnostic check done with a Porsche tester. Other testers don't always show the Porsche specific fault codes.
 
Just a technical question Richard.

Initially I'd thought the same as you, but this is a 2000 986 which presumably has the original Variocam system in which the actuator operates on the timing chain rather than camshaft itself, which features on the later Variocam/Variocam Plus systems?

I'd always associated reports of lumpy idle with the later systems, but I'm sure that there are similar components - actuator and solenoid - on the earlier system, although I was under the impression that it only operates at higher engine speeds, which presumably would exclude idle?

Jeff
 
Jeff,
from my understanding you are correct the original variocam solenoid is more Difficult to change out, specifically you’ll need a cam shaft holding tool to hold the Camshaft in place when removing the solenoid? However I was sure the solenoid could affect idle as-well providing much similar symptoms to those I have I’m just hoping this is not the case as it’s awful involved to change them out as far as I’m aware.
cameron
 
Cameron,

That's sounds like a tricky job without the correct tool. As Richard suggests, maybe it would be best to run some proper Porsche-specific diagnostics to confirm the cause before embarking on that route? As I said, my impression was that the earlier system only operated at higher revs as opposed to idle, but I'm probably wrong.

BTW, in case you weren't aware, Richard is a top-notch technical chap on the 996 in particular for which he's written an excellent Owner's Guide, so his comments are always worth noting.

Good luck.!

Jeff


 
Yes my thoughts exactly, I am planning on following Richards guidance on getting it set up on some diagnostics after this period of lockdown! Time will tell I will update the post with the answer - if I ever find one??!
 
Just logged back on to this for the first time in a while and thought I'd confirm what was wrong. I changed the camshaft solenoid to no avail and the actual issue was the actuator just for anyone's reference. thanks
 
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