949/996

I have '00 C2 with 35K miles. About a week ago, I was waiting at a red light and noticed the idle start to float up/down by 50-100 rpm. The check engine light flickered and then stayed on . It felt like the engine was misfiring at idle. The engine also misfires up to about 2000 rpm and then runs normal above 2K. Prior to this event the idle was steady at 800 rpm once the engine warmed up.

I took the car to my local shop Thurs 12/30, Hergesheimer in Lake Forest, CA. The tech read the fault codes which were misfire on #2, 3 & 6. Unfortunatley, the tech had not seen this problem before and did not get a chance to troublshoot the problem before they quit for the week.

I'm hoping someone has exerience diagnosing the cause of this type of misfire. It would be great to have some knowledge before I talk to the shop on Monday. Any help will be appreciated.

Horizontally Opposed Man

Is it still missfiring?If it isn't my guess is that your plugs could be fouled as well as maybe your injectors are getting too much junk built up in them my 2002 996 had a similar fault code at 35k plus.Your dealer can clean everything out and check the plugs my dealer recommends running a fuel additive once amonth through the gas tank when the tank is LESS THaN half full.Car has had afull recovery!

949/996

Thanks for advice to use a fuel additive on a monthly basis. I will discuss your experience with the shop tech.

The motor misfire has been consistent since it began a week back. However, I have not used any fuel sytem cleaner since buying the car and driving 3K miles in the last 6 months. I like the idea of using fuel additive regularly. I hope the misfire fix is this simple.

rrys

Could be water in the fuel. Problem with fuel pump or fuel pressure regulation. As the problem happened suddenly, and it affects both banks, it could be an electrical connector problem such as the connector on the air flowmeter. other common sensors, or a vacuum leak. Any unusual odors in the exhaust? I suspect you will get other error codes if the bad idling continues.

Ubermensch

Did you ever resolve this problem? I had exactly the same symtoms with a misfire only on #5. I ran techron fuel cleaner through the system and it definitely improved things but it wasn't perfect. I have 53k on the clock so I assumed the plugs were on their way out. I replace the plugs with stock but now I have misfires on #1, #4, #5, and #6! The car runs like crap as you might imagine! While replacing the plugs I noticed a number (4-5) of the coils had cracks in their body. I was concerned when I saw the cracks (most likely due to heat). Has anyone had their coil packs go bad on them, or am I going down the wrong path? Any advice would be appreciated before I drop a few hundred on new coil packs.

Thanks,

Shawn

Tool Pants

When I change the plugs I inspect the coils for cracks since this has been a reported issue.

Ubermensch

I didn't realize this was a common issue (seems like there are quite a few). I've identified that the cracked coils do correlate with the misfiring cylinders. I'll get some ordered up.

Tool Pants

I talked to a mechanic I know today because I saw a few defective coils in his junk box. He says the heat gets to them. What he could not understand, if this is your problem, is why there would be so many that are cracked.

Ubermensch

From past experience on other cars your mechanic is right on target. Generally the heat is the big issue for coilpacks in most cars. The fact the exhaust manifold wraps around that area has got be a killer. The heat shields in place don't look very effective. I may experiment a little when I get the new coils and see if I can find a better solution to make these last longer.

Tool Pants

Plus I was talking to him as a Boxster owner and did not mention it was a 996. We have the same coils but the exhaust manifold is not even close to them on a Boxster, unlike a 996. Good luck.

vljbeach

Anyone have a picture of these coils with cracks? I would like to know what I am looking for. I have misfire codes at low RPM's also on #3 and #6 only. Would like to get to the bottom of this.
Thanks in Advance

Sneaky Pete

Take a peek

https://www.google.com/search?client...ml%3B448%3B336

5CHN3LL

I have worked under the (mis?)conception for years that cracked coil packs were only problematic when wet, and other threads here have helped propagate this (at least in my reality)...