Alem12

Hi guys, a bit of a strange one. I have 2001 Boxster S with 76k miles and full service history. Two weeks ago (without any warning) the car started shaking while driving and engine light started flashing. This lasted for maybe 5 seconds and everything went back to normal except a loud knocking noise was now present. The noise was rev dependent but almost non existent at idle and high revs. The code reader indicated error on multiple cylinders. I drove the car to the 1st garage (about 10 miles) and there was no performance issue at all. The mechanic let the oil out and found pieces of metal in the oil. Now the strangest thing is since the new oil is in the noise is completely gone and the car drives really well. Anyone had the same experience? Any advice would be much appreciated.

Macster

Flashing CEL is a misfire condition harmful to the converters. That's a rich misfire.

There are a number of possible explanations. Bad injector. Bad fuel pressure regulator. Bad MAF. A piece of combustion chamber deposit broke free and got caught momentarily between an exhaust valve and its seat. Bad VarioCam solenoid/actuator. Maybe a bad crankshaft position sensor.

That the behavior apparently is gone with fresh oil is I think a red herring, unless the "old" oil was the wrong oil or its level was extremely low.

More likely shutting the engine off then on again "fixed" the problem suggesting it is of electrical in nature.

Assuming that piece of metal actually came from the car -- it is my experience that shops seldom bother to capture oil as it is drained and then take the time to rummage around in it for anything -- the piece of metal is probably just something left in the engine from Day #1. The shaking may have caused it to move from some back corner of the oil sump to some place closer to the drain and when the oil was drained it was carried out with it.

If one is concerned about metal bits in the oil carefully removing the oil filter housing and dumping its contents into a clean drain pain is of more value. The metal bits are stopped from continuing by the filter. So they collect in the housing. But like oil draining what happens is the tech loosens the filter housing and just pulls it down and turns it upside down and lets the filter element fall out and then housing drain for a while.

Absent any symptoms to go on about all you can do is just drive the car and see if the behavior returns. I'd be less inclined to continue to drive the car though. I would carry an OBD2 code reader to have to plug in -- without shutting off the engine unless it is running real bad -- and reading all codes, including the code associated with the freeze frame data (and the freeze frame data), pending codes and permanent codes and writing all this down.

You can then shut off the engine. If upon restart the behavior returns I'd recommend you err on the side of caution and arrange to have the car flat bedded to shop. If upon restart the behavior is not present then with some caution and ready to at a second's notice pull over and turn off the engine if the behavior returns drive the car home and arrange to get it in the shop. You want a shop that is highly experienced and trained to work on these cars.