Hey Guys,

My SC'd 996 is experiencing random misfires on pretty much all cylinders.
This happened suddenly and without warning, it was running really strong up until last friday. It's misfiring through the entire rev range and eventually the computer just switches off the offending cylinders.

I pulled some of the plugs and they looked ok, and the coil packs look ok too.

I ordered new plugs and coil packs anyway as it can't hurt to replace them anyway since the coilpacks look like original equipment.

So, then I thought I'd check the MAF to make sure it was clean and also check the airflow from the SC to make sure it wasn't clogged up.

While I was pulling the MAF I noticed two things that struck me as odd. The first is a dangling wire with some sort of sensor on the end of it.

Is it a temp sensor ?
Where does it go normally ?
The second is a connector with nothing plugged into it.

Any idea what both of these are ?

Any help would be very gratefully received. I thought I'd try the obvious things before calling the Sharkwerks folks and seeing if I can get to see the Doctor.

:-)

 

The 1st pic is your temp sensor that triggers your fans up front. It goes in between the the 1st and 2nd air distrib tube. You have 3 on each side. If you have a PET you can find the diagram. Don't have it handy.

I can't tell where the 2nd picture is. Need more surroundings to get my bearings.. maybe somebody else can chime in here?

 

Found ya a picture. It is the thing at the top sticking up between the two air distrib tubes. So directly below the O in PORSCHE

 

Yes, I thought it was a temp sensor of some sort. It was dangling in that general area, so maybe it popped out. I'll see if I can take a better picture of the other connector too, it's hard to get in around the charge cooler.

:-)

 

That second connector is normally off, I believe it is a spare and is used for some other options.
heres mine on my SC 3.4, during installation... its part of the rear harnesses

 

The first picture is for the engine compartment fan operation and has nothing to do with your front fans. If the cable is removed from this sensor, your fan will run.


As far as the misfires....disconnect the MAF connector and see if they go away.

 

Ooops. thanks for the fix. That's what I get for going from memory. At least I succeded in accurately showing him a picture of where to stick it. Ooops again. LOL Just having fun fellas.

 

hey simon, glad you "enjoyed" (heh!) changing those plugs/coil packs... They do go bad after time/miles and glad it fixed things

Merry Xmas!!!

 

Yes, oh yes, that was indeed fun.
The bleeding and swelling have stopped now, I expect to regain full usage of my hands in the coming days.

:-)

 

so is it fixed? What happened?

 

Yeah, it's fixed but it's weird.

It was misfiring on all cylinders. Random Misfire P0300 plus lots of other specific cylinder misfires. It's weird because it happened all at once. One second it was running strong the next it was pulled over in the lay by with me reading the codes with my trusty OBD scanner.

I limped the ol' girl home and re-read the codes again (it had switched off most of the cylinders on the way home, presumably to protect the cats)

Random misfire again, plus the usual suspects on specific cylinders.

I suspected a vacuum leak or a faulty fuel pump, neither of which I wanted to attempt myself at home.

I figured if I take it anywhere to be looked at, the first thing they will want to do is replace the plugs and coilpacks, so I decided I'd do that myself before hand and just rule it out, since my labor is free and to my knowledge the coil packs had never been done. The plugs had been done by Sharkwerks the previous year and either sharky or James did mutter something about coilpacks at the time, but I forgot what they said and just blindly carried on as normal. Pedal to the metal with one eye on the mirror looking for California's finest.



I shuffled around underneath that mother.... for 4 hours pulling the plugs and coilpacks. They are not easy to get at. I did have two "learning moments" along the way though.

1. When you disconnect the wires from the coil packs, pull the sheath back WAY WAY back, rather than just pressing the catch through the rubber sheath. It's damn near impossible to get them back on, or peel back the sheath when they are disconnected otherwise.

2. Check there is nothing obstructing getting the connector back into the coil pack before installing it on the car. Three of mine had random bits of plastic floating around in the connectors that made me take them off and re-install them after removing the offending bits. You'd have thought I'd have learned after the first one, but ohhhhh no.

Anyway, the plugs looked fine, but the coil packs looked like original equipment, and replacing the combo made all the difference. runs nice and strong again now.

I've been tooling around in it all day today and it's been fine.

I really appreciate all the advice I got here too , I hope one day I can return the favor.

 

hey simon, i have an 03 911 c2. i had the exact same problem about 5 months ago. same code. misfiring on 3 cylinders. i hobbled the car to a very respected independent porsche garage. they kept the car for a week and could not find anything wrong except some loose wires. while there i had them change the oil and the air filter. got the car back, i think about 400 bills in charges, the car ran fine for about a month. while in maryland i felt the car was hesitating a bit too much so i took it to another garage and told them to change the plugs. while in the process they told me my coil packs were fried, so they changed them as well. so far so good now.