Magdaddy

09 GTS, recently started to slightly stumble at low rpm’s, at about 3600rpm she takes off like a rocket. In April of 2019, at 82k miles, all three fuel pumps, and filter were changed at the selling Pcar dealer. I’m rolling 153k miles now. A couple misfire’s were noted, but no specific fuel codes. My Indy noted that pump 1(left according to other threads here) was off until that RPM range around 3600.

Tank is 1/4 full, as I also read that pump operation can depend on fuel level.

the stumble doesn’t care about tank level, seems consistent from full to below a 1/4 tank.

So…70k miles on all the fuel pumps, and filter…super majority of the fuel likely bought at the same place, as this is my DD.

Thoughts?

Dr. 914

could be one of the coils misfiring

Magdaddy

all plugs and coil packs replaced two summers and about 30k miles ago

Petza914

Put a scan tool on it and monitor the individual cylinders for misfires while you recreate the stumble to see which cylinders are causing the stumble. If all on one bank, that points us in one direction, if a single one, a different direction, if on both banks, yet a different direction.

Libast

How's your torque arm look?

Magdaddy

I don’t remember the cylinder’s, they were cleared before I wrote them down. I think it was 1&4

Magdaddy

that yellow poly insert about three years ago….forget the manufacturer.

Petza914

If both on the same bank, look for a vacuum leak on that bank or odd camshaft deviation numbers (or all zeros) from that bank that would point to a bad camshaft.position sensor.

TomF

Powerflex...https://www.powerflexusa.com/shop/pr...m-bushing-3738

Magdaddy

Update…stumble now noticeably worse with less fuel in the tank, almost undriveable.

most recent codes:
P1559-power supply without engine operation
P1378-valve lift control, cylinder 8 small
P0301- cylinder 1 misfire detected
P0687- ECM/PCM power relay control circuit high
668-vehicle voltage, terminal 30
446-function restricted due to undress voltage
532-power supply

Long conversation with a trusted shop in CT, about other upcoming Pcar work. Discussed the rough running issue, he suggested changing BOTH in tank pumps.

At acquisition, 82k miles, both in tank pumps, filter, and HPFP were replaced, as well as a few associated hoses. Turning 155k 3 1/2 years later.

No record of the L&R sending units, nor pressure regulator being changed at that time.

so…questions:
-what is the age/mileage expectancy for the in tank pump’s?
-same with other bits in there

My Indy is limited in how deep he can dig, above mentioned faults were identified with his unit.

I’m still 4 weeks out with my local Pcar dealer appointment…they apparently have but one tech, and there’s a 7+ week leadtime for service. Good time’s!

ute is not good to drive, pops and burbles sound kinda cool…but the grotesque stumbling and occasional backfires are doing nothing any good.

Priced up both pumps, fuel filter, both sending units, and regulator. A mix of FCP Euro and dealer…God only knows what Porsche actually has available.

thoughts?

Ryanschoolya

How old is the battery?

Magdaddy

changed almost immediately after acquisition…less than 4 years old.

Ryanschoolya

Cayenne are super sensitive to lowish voltage voltage. I would double check that.

Chris M.

Have you read about the random codes/errors/issues caused by the driver’s footwell wiring harness getting wet?

Cabin Floor Flooding

Magdaddy

did a half hearted attempt last week on this. Drivers floor didn’t “feel” wet. I do annually clean all the drains. Probably a good idea to get aggressive with the sills and carpets, for a deep dive.