Hi fellows, new to the porsche community, recently purchase a 2004 speed yellow c4s. I've use the search part of the forums for some info, I recently had an issue where the pms/abs light came at a high rate of speed and shut the car down. Mods done to the car is k&n filter gt2 spoiler, and cat back exaust done by the previous owner any insight into the problem will be highly appreciated.

Thanks, Kevin.

 

First off, welcome to the 996 forums! Second, your choice of a C4S was a good one I'm going to assume you mean PSM and ABS, so let's start there.
Make sure the brake fluid is full.
Make sure the brake pads are A,OK
If all those are in good order, then it's more than likely the alternator, battery, and voltage regulator. Perhaps not all, but get the Alt checked first because those warning lites are more sensitive to low voltage than the battery lite, why you ask? Who the heck knows
But this is where I would go if the fluid and pads are ok.

Jim

 

Thank you. Yes that's what I meant,autocorrect. Car just pass a ppi brake fluid is at the proper level. Brakes have 7/32 on them, previous owner replaced the alt,and battery last year. Some say it mite be a maf sensor,it doesn't do it all the time, but then again it only does it at a high speeds.

Thanks for the input Jim.

 

check front/rear tire size

 

Front and rear tires are the correct size their OEM, they do however mite need replacing in the near future.

 

The MAF would throw a check engine light. Sometimes if they are over oiled it will mess with the car. Also if you get the car washed or it is in some rain for awhile the filter gets wet and will make the motor run bad.

 

The idle was kinda rough when the PSM/ABS light was on after it stalled out at a high speed run. The car did sat outside for a while before in the rain, but no problems at normal speeds.

 

Normal speed you're not sucking in as much air. When you're getting on it,it will pull every bit of water out of that filter.

 

I guess it doesn't help to have the open vents on that GT2 misha wing,and a K&N filter.

Thanks, for your input I highly appreciated.

 

Try having someone look at your brake lights while you're pushing on the pedal. Quite often one gets those same signals caused by the brake light switch.

 

Thanks I'll have someone look at them today.

 

Make sure the battery is in good order, it could work fine but it may not be accepting the full charge, ie 13 volts.
It it's happening while you're driving and it's raining then it could be the filter/maf getting wet. You could try the sock or if so inclined go back to the original air box and put in a high flow filter, K&N, EVO, or BMC, and then add the silicon air intake. I've been using this set-up and it works great, and you don't suck alot of air from the engine compartment.

 

I will put the stock air box on and take it fast and see what happens.