Unstable idle with air filter removed...
 

Some of you may have known that I'm using the Evo Highflow setup and experienced a drop in bhp/torque. A couple of reasons suggested by some are :

1) Bad MAF
2) Insufficient incoming air volume
3) Leakage

To prove (2), I wanted to replace the air filter with a double layer of fine wire guaze over the intake pipe with the intention to dyno the car again afterwards. Reason being the supplied K&N filter has a much smaller surface area compared to the stock paper filter. Hence, if I experienced a power hike upon removig the filter, the fault probably lies with the filter's smaller surface area.

However, upon removing the filter, the idling immediately became unstable and was hunting. This goes away once I put back the K&N. The increase in airflow obviously caused some undesirable effect. Is this supposed to happen? Is this a sign that my MAF is screwed :(

Under normal circumstances, a less restricted intake will result in higher idling but not supposed to cause unstable idling right?

Hope someone can point me in the right direction :)

Finally, is there any sure way to find out whether my MAF is screwed?

I do know that the MAF in the Boxster is made of different materials than most MAF out there. Therefore, it MAY be that you will not obtain "normal" responses from chantes like you made, as compared to other MAFs you may have worked on.

Are these EVO folks of no help here? It seems THEY should be the ones troubleshooting this issue instead of YOU and with THEIR nickle, not YOURS.

Do you have a friendly parts dealer than can sell you the MAF with a money back guarantee?

:rolleyes:

Doesn't the Boxster uses the same hot wire concept for their MAF? I'm really not sure.

With regards to approaching EVO for help, I don't think so... They'll probably go ask me to fly a kite :P And to start with, I didn't get it direct from them but through MidAmerica. Moreover, it doesn't help that I'm not local :(

Right now, I'm just hoping there's a way to tell conclusively whether the MAF is faulty or not....

I think the strategy is to find a supplier that will allow you to retun the MAF if this is not the issue. Have you made any calls of that type?

Yeah, see if you can get a refund.

Clubhead,

Call Evo. You're assuming they'll tell to piss off. But on the other hand, they've wrenched on a lot of Porsches and might just give you the answer without having to "guess", which is what all of us are doing here.

With that said, your idle will stumble when you take out the filter. It is suddenly seeing a ton more of unimpeded air and the computer doesn't know what to do. I used to take the filter out of my M3, run the car and shoot injector cleaner in to clean out the idle sensor, etc. With one hand on the throttle linkage, it would still buck like a bronco. So what you're seeing isn't out of the ordinary.

I would attack the problem with:
1. Call Evo.
2. Run dyno and get a/f readings.

The only supplier over here for Porsche parts is the OPC themselves. And there is only 1 agent here, sole distributor :( Monopoly if you call it. Local market is too small to sustain > 1 agent. So no, I'm not going to get that kind of chance to return the MAF...

Bummer! :(

And found out today they're asking US$700 for the MAF :(

Hmmmm... I may just call them to find out. Let's see.

Meanwhile, I've explored putting in a wide band lamdar sensor to read the A/F mixture. But the mechanic here says unless the MAF is way screwed, the A/F will still be in the region of 12-14:1 And if the MAF is way screwed, you don't need the sensor to know things are wrong. You can smell it from the exhaust. Oh well...