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Old 05-09-2013, 05:28 AM   #1
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Boxster Dies on Tickover

I have a 1998 2.5 Boxster 60k miles.

I had a serious misfire last year and after changing plugs and coil packs finally took it to OPC which diagnosed both failed O2 sensors. At that time they disconnected both to make the car run slightly better on my return journey.

I changed the sensors and the car ran perfectly when cold but when the engine reached operating temp it ran rough at tickover and often stalled at junctions. I had a fault code of 'left bank misfire' and random misfire. I swapped the O2 sensors between the banks suspecting one might be faulty but it made no difference.

I then discovered that the MAF had been disconnected, presumably by the IPC, and when I reconnected it the car ran appallingly with heavy misfire in the mid range. I concluded that it was faulty.

I have now replaced the MAF and the car runs brilliantly with the exception of the stalling when I stop at junctions. This only occurs when the engine is hot, not when cold.

Any suggestions?
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Old 05-09-2013, 08:09 AM   #2
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This could help, not 100 % sure but it should not hurt. First look and listen for a vacuum leak any of the small black tube that cross over the engine from the vacuum canister (passenger side) to the vacuum switch (Operator side) then to damper plate in the front crossover pipe bottom side. If no leaks disconnect the battery for a minute or two then connect it again.
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Old 05-11-2013, 08:07 AM   #3
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^^ A good point. Another place to check for a sneaky vacuum leak is the filler neck for the engine oil that runs down from the area where the oil cap is in the trunk. If it is cracked somewhere though, it'll need to be replaced.

I was also wondering about fuel, but not thinking that's too likely a culprit because you're running fine until it gets hot.

Question though: When the car stalls as you come to a stop, how does it act on restart? Is it hard to start back up? Does it run fine for a bit before acting up again? Does it immediately start running poorly again?

Like jsceash pointed to, though, you're probably looking at a vacuum leak somewhere, and sometimes they're in really stupid and/or annoying spots you wouldn't even suspect. If you're still not having any success after the checks he mentioned, maybe take a look at the heads to see if the gaskets are leaking.
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