subparrnd

Any updates on this at all?

Macster

My info is that if misfires are detected and the tank level is low misfire error codes will not be logged.

Now there may be other error codes that can be logged even though the fuel tank level is low, and may (though I can't think of any off hand) even be triggered by low fuel level. It would help to know what the codes were.

If the 997 in-tank fuel pump is similar to the one in my (fuel filterless Boxster -- no serviceable fuel filter) the fuel pump intake has a large area of fine mesh so unless someone dumped a pillow full of goose feathers into the gas tank while you weren't looking I doubt there's any blockage at the pump intake end.

However, stranger things have happened.

The bit I've read in this thread suggests the problem is a fuel supply problem which may be at the HPFP but the techs tell me that this pump can 'look' bad from a low pressure fuel pump that does not keep the HPFP supplied with sufficient fuel at the expected fuel pressure.

Sincerely,

Macster.

TxBob74

Finally, an update worth writing. After going back and forth with the service advisor and finally getting the car back this evening after talking with the SM this morning, it seems the problem is not fixed.

Service manager told me that they have been working on resolving the problem with PCNA's assistance. No hardware problems were found, but in the course of inspection they had disconnected and reconnected several wiring harnesses. No more codes for several days, so the car was deemed safe to return to the owner, with PCNA's concurrence. SM said that my final problem two weeks ago with stalling was due to the car going into limp mode after so many codes had been thrown. Very light throttle had gotten me home.

Picked the car up this evening and all was normal until I was finally able to reach freeway speeds and lightly accelerate. Car was fully warm (oil T at 200F). Shortly after passing 65 mph in 6th gear, the problem happened again, though without a CEL. So I stayed below 65 mph and 2800 rpm the rest of the way and had no further problems.

So now that I know how to drive the car in its current state, I will call the other two dealers, check their confidence in solving the issue and demonstrate for them before leaving the car. This time I will leave with a loaner, though.

One issue with fuel tank level. Should I only be able to add 12.74 gal from onset of low fuel light? Dealer didn't add much and I was unable to find a station until tripping the low fuel light (and gong). Filled it shortly thereafter and that's all it would take; gauge now reads sliightly over full mark.

As far fault codes, here is what my invoice reports:
P0077, P0083, P0300, P0301, P0303-P0306, P0350, P2302-P2306.

Yes, 14 of them. SM said the codes relate to low DME supply voltage. Upon seeing the list, they seem to be in at least three areas though. Again, no hardware issues were found and nothing was replaced. From the codes, SM concluded the problem is ignition related and not fuel supply.

The saga continues tomorrow......

Alan C.

Bob,

I sent your codes to my dealership on the chance that they may have come across something like this in the past. If I hear anything I'll post it here.

Jok

What fuel octane are you using..?

RollingArt

Since the problem has only appeared at full operating temp I may begin to suspect a sticking lifter. The lifter expands with the heat and looses operating clearance.

That's my WAG.

GL getting this resolved.

TxBob74

93 octane is available here (Houston). Filled last night with Exxon; usually use Chevron or Shell.

The problem is throttle position sensitive, too, since I can travel a steady speed on level roads at moderate speed (<65 mph) without incident. Accelerate moderately even at that speed and the problem is likely to recur. Accumulate enough incidents and the DME apparently shuts it down.

I set up a service appointment for Wednesday morning at Porsche North Houston. I completely explained my prior experience with Momentum to the service advisor, Jim Maxwell. Mike Molina is touted on their website as able to handle the tough diagnostic issues and we will take a test drive to demonstrate the problem. Any greater Houston folks familiar with him?

So there won't be further developments on my end (assuming the car doesn't have any issues over the weekend) for several days. Any and all ideas are welcome! Macster, are you able to make sense out of the fault codes?

utkinpol

imho dealer just plays dumb with OP hoping customer will give up and take car back.
i had similar stuff played to me when i wanted to get clutch bearing replaced by warranty - master tech looked at it, agreed that clutch should be opened up for review< i left car to them for a week and in the end they did nothing claiming 'there is no issue we could detect and reproduce'. typical dealer`s BS.

Alan C.

Hearing this makes me happy that I have a great dealership to deal with.

stronbl

I'm sure the last thing you need is another opinion on this and would rather have a solution. But ... your problem sounds very similar to one I had many years ago on an old CJ-5 Jeep. I replaced fuel pump, fuel filter, distributor and cap and still no solution. When the car was cold to warm everything was fine; I could drive at hwy speeds. But when it reached normal operating temp, then it sputtered and kicked and eventually lost power to the point all I could do was limp around at about 15 - 20 mph max. Since it was so old ('76) it had no real computer codes to shut it down. I was frustrated and finally spoke to a real mechanic friend who ran an auto parts store. He told me to replace the voltage regulator. It was a sealed unit and a simple plug-in replacement. That was it, the voltage regulator had gone bad ... problem solved. So now whenever I hear of these type symptoms, I always think voltage/spark in addition to fuel. Any chance your p-codes could suggest a voltage regulator issue? Just a thought. Hope you get a solution soon and best of luck.

TxBob74

The service manager did say they tested the alternator and it was OK. I imagine the votage regulator is built-in with the alternator, but have no knowledge other than modern cars are usually built that way.

This could explain the low DME voltage problem though, which was the only fault code mentioned by the SM. Perhaps the spark is not strong enough for higher cylinder fuel loads? I will mention this to the new service tech next week. Thanks much. Maybe very very much!

Would be amazing if a '76 Jeep and 2011 Porsche with (almost) entirely different electrical and ignition systems could suffer the same symptoms and root cause.

TxBob74

It will get very interesting if North Houston reports back next week that Momentum had not been working with PCNA. North Houston is owned by Indigo Auto Group and would have no problem reporting this. Both Momentum and West Houston are Sonic owned and would have no problems collaborating.

stronbl

Just make sure when North Houston tests they do so at cool and hot engine temps so they can see if there is a voltage leak/malfunction differential. May want to see if they can simulate an engine load too (ie your comment about acceleration going above 65 mph at normal engine operating temp).

TxBob74

The repair saga continued today. Drove 40 miles to the North Houston dealership without incident. Picked up a Tech and test drove up to 80 mph over a 15 min period, again without incident. Tech took the car into the shop and found a fault code not in his book. They definitely want to check some things out and I left the car with them. Speculation from the symptoms is a relay powering the DME is not functioning properly due to road vibration.

Anyway, after talking with two Techs and the service advisor, I have more confidence that they will make a better attempt at repair than Momentum. If nothing else, replace the questionable relay.

mdr2001

TXBOB,

Sorry to hear about your continuing issues, but I can say that I worked with Jim several weeks ago and had nothing but confidence. To be fair is was a known issue and not a major diagnostic job, but I still left feeling pretty good about North Houston Service department.

Hope this round fixes the issues. Keep us posted.