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Read my post #20 about it for more details.... It is also documented on another thread in which was discussed in greater length.
Basically, It is not the wrong/lower alternator speed but rather the pulsations it makes when the belts slips rapidly due to incorrect size and being "pinched". At higher rpms, the belt slips ever so slightly and then it catches again once the tension from the "pinch" is released.
Due to the rotational inertia of the alternator, those pulsations are transfered to the crank, where they are detected by the crank sensor and the ODBII logic reads it with a multiple misfire in a all cylinders.
Now I bought it. Thanks for explaining. What a phenomenon!
Note to anyone doing the serpentine belt. Use a Porsche belt from the dealership. I bough an aftermarket belt Dayco belt from a local auto parts store and within a thousand miles developed misfire codes on all cylinders: P0300, P0301, P0302, P0303, P0304, P0305, and P0306. (yes it is hard to believe and harder to explain that a belt can cause misfires but there were several cases reported here and Planet-9 so I gave it a try and swapped to a Porsche dealer purchased belt. Misfires are gone and I have put close to 1000 miles on the new belt to include spirited fun runs, Auto-X and long highway drives.) I'm sure others have replaced with Dayco or Continental belts without issue, but it's not worth taking the chance on having to do it twice imho.
Hmmm, I'm curious: is this malady of crank sensor reporting misfires limited to OBD2 cars, or are OBD1 cars equally susceptible. I know there is lots the obd2 monitors that the 1 does not so, again, just wondering...
Omg! I just spent $2500 replacing plugs and wires to try to resolve the misfire codes. Looks like I have non-OEM belts! Not to sound like a total idiot, but can someone look at my photo and verify that this is correct?
Also, I assume they all need to be replaced?
U
gh why didn’t I search RL before spending the 2500 lol!
Nah. Just replace the dayco one. There is a lot of valuable info in this thread. I've been chasing a misfire code for about a year now since doing my Clewett install. I'm thinking I may need to do the lightbulb fix.
Andreas, do you still have those instructions on adding the bulb to the rear relay/fuse panel?
ahhprods,
You definitely don't need to replace the one for the AC compressor. As for the the other two - I'm not sure if those are OE brands or not - I'll leave it to someone else, but on one of them you can see the size is the OE size of 9.5 x 760, and not the odd Continental size of 10mm.
The thing that's strange to me is why no one talks about the voltage at the alternator and/or the battery and why the ECU is not reporting "Voltage Supply" errors. Has anyone measured the voltage? ...or do we think it's just randomly slipping so causing weird transient drops?
Ok nvm shop says my belts are all oem cuz they say “porsche” on them. They think if anything could be the flywheel issue that I’ve seen in other posts. Sigh… I should just be smart and just sell it.
Omg! I just spent $2500 replacing plugs and wires to try to resolve the misfire codes. Looks like I have non-OEM belts! Not to sound like a total idiot, but can someone look at my photo and verify that this is correct?
!
Originally Posted by ahhprods
Ok nvm shop says my belts are all oem cuz they say “porsche” on them. They think if anything could be the flywheel issue that I’ve seen in other posts. Sigh… I should just be smart and just sell it.
Hello @ahhprods, right, your belts are all OE (Original Equipment) belts as they have the Porsche branding on them. Not to be pedantic, but you mean "OE" not "OEM." OEM = Original Equipment Manufacturer. An OEM part is something that is made by the manufacturer of the OE part with Porsche branding, but not sold at Porsche dealerships, and thus does not have Porsche branding on it.
The reason to distinguish between OEM and OE is because the term OEM is so often abused in the industry.... FCP Euro being one of the outfits that consistently adds to the confusion. For instance for brake pads for the 993:
ㅤ
OE = Porsche branding. These are made by Textar for Porsche
OEM = Textar branding without any mention of Porsche. These pads are in in fact different from the OE Porsche pads (lots of discussion over the years about this on RL - see here for example)
OEM = Pagid branding without any mention for Porsche (??????) See below screenshot @ FCP. Pagid surely makes some brake pads for Porsche, just not the Porsche 993. But retailers will apply "OEM" to describe the part.
This issue surfaced some years ago and people like Steve Weiner(we'll miss him) and similar others shared long experiences with OE v. OEM belts. The overall conclusion- use OEM, even though they're a bit more $. There are very slight differences in width, underside rib patterns, and circumferences among OE belts.. It seems in some cars it's a non-issue, but in many it is. My car had an OE fan belt installed and correctly tensioned. It was printed Porsche, and was Dayco. Misfire codes immediately appeared, although the car ran perfectly. Belt swap to Porsche OEM from the dealer- no issues. The fan sensor wheel assembly was not at fault.
This issue surfaced some years ago and people like Steve Weiner(we'll miss him) and similar others shared long experiences with OE v. OEM belts. The overall conclusion- use OEM, even though they're a bit more $. .
I think you mean "Use OE." (Not OEM). Always use OE ORIGINAL EQUIPMENT belts. These are belts purchased from Porsche. Do not use belts that are sold as OEM Original Equipment Manufacturer Belts.
07-27-2010, 10:08 AM
shop says my belts are all oem cuz they say “porsche” on them. They think if anything could be the flywheel issue that I’ve seen in other posts. Sigh… I should just be smart and just sell it.
