black996c2

Hi,

Took my 996 for a short drive today after sitting in the garage for 3 weeks, drove fine to the mall. On my way home, started acting funny, loss of power, stutter under acceleration, check engine light flashing. Oil pressure fine, feels smooth with no accelerator input, get into driveway and idling steady but sounds weird/lumpy. Pulled the engine codes. 7 codes;

P0507 - engine rpms higher than expected
P0300 - random-multiple misfires detected
P0202 - injector circuit open - cylinder 2
P0301, P0302, P0305, P0306 - cylinder 1, 2, 5, 6 misfires detected

Car has 71k miles. Recent work within last year - IMS LN retrofit done during clutch replacement, couple engine pulleys replaced, ignition coils replaced along with throttle body cleaned. Change oil every 5k miles at dealer. RMS and AOS replaced. Typical "common" 996 problem issues addressed.

Any ideas? Going to likely have the car towed to the dealer this week. Dont want to risk further damage driving her there. Thanks in advance for any input.

Macster

Well, you won't like to read what I have to offer: Mice.

3 weeks sitting and all of these appear out of the blue. It ain't bad gas.

Well, I hope it is, that is I hope I'm wrong and it is something less serious than rodent damage.

And I could be. If an injector has decided to fail -- which the P0202 code suggests -- the DME will add more fuel to the other cylinders of that bank and these can misfire due to too much fuel. Or if the injector failed open the DME will cut back on fuel to the other injectors of that bank and misfires result. The misfires on the other cylinders -- those on the other bank -- can be sympathetic misfires, spurious misfires arising from the fact the engine is just running so lousy.

Don't mean to be all gloom and doom so soon after a holiday but my 2nd hand info is -- what I was told when I came upon some cars in for rodent damage -- is when mice are involved the owner has to fall back on his home owners insurance to cover the high cost of putting the car right. Thousands of dollars can be required. In one case a new engine wiring harness was required -- among other things -- and the engine (a Turbo) had to come out to get this harness out and to be able to check for other damage in the engine compartment. I do not know what other damage was found in the cabin/AC system, etc.

Don't run the engine anymore until after it has been sorted.

Get the car flat bedded to a dealer pronto.

You'll know soon enough if its critters or injector or something else.

Copilot

RATS??

Make that 25 modes of failure

mklein9

Something that sudden and severe is likely to be electrical. As Macster suggests it could be mice. My '02 developed something like this -- and I tell you the misfiring was severe -- and it was finally traced to corroded engine connector pins. This was right after an engine rebuild. It was also highly temperature dependent and initially inconsistent but got worse over time.

If any of the engine connectors were disconnected and reconnected, this might be your issue as well. 12-year-old connectors will have developed corrosion; when they are taken apart and put back together it is possible some of the pins will not precisely match up against the uncorroded parts of their mating halves and will make unreliable contact.

What to do first: order a can of DeoxIT DN5, take apart the engine connectors likely to be involved in the signals the DME is complaining about or that you know were taken apart recently, and spray both sides of the connectors.

The "unexpected RPM" code might indicate the crankshaft position sensor on the left (driver) side of the very front part of the engine where the flywheel is. While my connector corrosion problems were occurring, I was racking up Range 2 overrev counts probably due to weird signals from this sensor; it was certain the engine was not in any overrev range.

But also look for actual damage or evidence of critters.

riddler777

from my experience on 98 car it was a dead camshaft sensor, only i had codes for cylinders 4; 5; 6; plugged new one in, all gone, if your car is newer it might have two camshaft sensors. maybe both are dead/dying, I never had a code on the sensor itself

Gonzo911

It's always mice...

black996c2

Ok, so after flatbedding my 996 to the Porsche dealer yesterday morning at 8am, I just heard back from them. This is what I was told. "While digging around in the engine compartment and checking connections, they must have bumped something as the car is now running properly. They feel something on the harness or an injector wasn't sending but now is. The injectors appear to be fine but I could have injector that could have been stuck open or closed which caused a lean cylinder misfire. They were able to clear the fault codes and road test the car and everything now appears to be fine."

Any thoughts?

alpine003

Yeah it's fine now so drive it or worry some more and don't drive it.

If all it took was a little jiggle, jiggle around and see if you can replicate it or wait until it happens again and jiggle it at that time.

george996

a few comments. Just for information P0507 is "idle air control at stop - above limit" for DME 7.8 as in your 2003.

Here is my guess - P0202 "fuel injector cylinder 2 - open circuit" is the root cause for all the faults read because 1) the DME will record P0202 only when it detects an open circuit, no other reason that i can determine and 2) a closed injector (open circuit) in any one cylinder could cause misfires.

I would expect the problem to show up again unless the dealer clearly found a loose connection.

Macster

Well, if it is not mice then it is last thing touched first thing suspected.

While it is not that common for something to pop up some time (and miles) after servicing work it is not unknown. (Example: On a road trip and on one of the loneliest stretches of I-40 in AZ my '96 Mustang developed a hesitation. I can't recall if the CEL came on but the hesitation right where the RPMs wanted to be for a nice cruising speed were real enough. Long story short I found a plug wire not connected securely to a plug. This had been loose for a while for the tip of the plug had eroded some enough that the plug wire connector no longer snapped on the plug. I bought a pair of pliers and squeezed the connector some so it fit on the plug securely and drove on to a town further down the road that had a Ford dealer and bought a new set of plug wires. The "fix" never acted up and I sold the car some years later with the box of plug wires in the trunk unopened. I can't be sure now how many miles I drove the car after the plugs were changed, but I believe it from Salt Lake City (where I had the Ford dealer replace a leaking radiator and change the plugs) to KC Mo and then back to someplace close to the NM/AZ state line. I'd guess I drove at least 2K miles, maybe more.)

My thoughts are just resume enjoying the car though keep a bit of a look out and an ear open for any other issues but I don't expect any to appear.

Red998

Thank you for this thread. I had similar situation with misfires and codes. Car is at 85K miles, and while at track day CEL came on with P0300, P0301, P0304, P0305. There was a shop on site who pulled same codes except P0303 instead of P0304. They cleared the codes and car was misfiring like crazy. Then P0507 showed up. Car idling at 1200 rpm. The checked injectors (new), MAF and O2 sensors. They did not get a reading from the O2 sensors. I had just put new O2 sensors in. I dropped car off at my indie. The vacuum line came loose and the brake vacuum line was also loose. All codes gone. Just in case someone is trying to DIY this problem which could be many things.

riguardli

had similar codes mess
the issue was: