About a 3 weeks ago I got a ECU fault (yellow) on startup.

I don't get too worked up anymore when I first see these, as it is a "drive on" fault and I've gotten them before (recently I posted about the P0456 emissions fault that ended up being caused by a obstructed drain line).

But I've noticed that several times over the last couple years I've received ECU faults after refueling. And then they subsequently go away after the next refuel. Hmm.

But this particular fault, started out as an ECU yellow fault and after driving the car for about 10 minutes, I had an almost complete loss of power and then the instrument panel lit up red. still an ECU fault but indicated "drive on".. Basically I nursed the car off the road at like 3 mile an hour as there was almost no power. (still with a Red fault but indicating "drive on").

So I shut the car off and after restarting, something kind of weird happened and the car seemed to have gone through some kind of "reset"... But the entire PCM went through it's reset (which I've only seen when it crashed while playing an MP3 file) I'm not sure I'm describing it properly but the result was I had now only a yellow fault. And for the most part the car had power again.

Normally I would have probably just parked the car, but because of the circumstances and I had an urgent meeting I continued to my destination. For the most part the car the engine ran properly, but I did notice the tach was jumping around quite a bit at idle...

One additional bit of information was that I had just refueled about 2 miles from my house the previous night after pretty much having been on just about empty. Also note it was after several days of intense rain in the so cal area.

So I started to convince myself somehow I must have contaminated fuel again. As mentioned this isn't the first time I've gotten an ECU fault because of fuel. When this has happened previously, it seems to have occurred (or I believe) that the gas station had either accidentally (or I'd like to believe) had lower grades of fuel in their premium tanks. Note In California the best grade available is only 91 octane. which is less than the 93 Porsche recommends, but the ECU's seem to de-tune properly and I generally have no issue.

But what was different about this was that initial incident with a red fault where I ended up with absolutely no power. Something was clearly wrong.

So later in the day, I topped the car off again with premium fuel (another station) in an attempt to dilute whatever fuel I had. But could only get about 5 gallons in the tank. By now the car seemed to be basically running ok (although the tach still seemed to be fluctuating at idle, but it could have been that I was paranoid by this point).

So I allowed myself to get down to just about empty and then refueled with premium (91 octane). My expectation was that a good tank of premium should fuel (from another station) should clear the ECU fault. But nope drove through another tank and still had the ECU fault. So I was resigning myself that something else might be going on. So far I hadn't pulled out the Durametric to check the actual fault code.

This morning, just about on empty, Got fuel (at another station) and immediately no Fault at startup. Which is normally what happens when I get one of the faults.

So now that I've experienced this ECU fault after fueling on several different occasions (this being the most severe). I'm really starting to believe that this "accidental" getting lower grade fuel may be happening much more often often than I thought. In this case I went through two full tanks of premium fuel from two different stations and brands.

This is happening enough that I'm starting to question if there is some sleaze going on with certain stations. Too often to be "accidental".

So far I seem to have gotten inferior grades of fuel at more than one station and fuel type: I know of at two Shell, a Mobil and an Arco. I can see how a say water contamination could occur (although the station owners all claim that they have water separators so It can't happen).

I guess I'm going to start to be really picky about where I get fuel.

Now it could be related to in California we only get 91 Octane the car may be a bit more sensitive. But I'm not sure what the octane is of the other grades in other states. I'm also not sure what the seasonal Ethanol addition does as well. I do know that the ethanol addition tends to cause more problems with residual moisture in the tank.

Starting to get a bit paranoid, and am starting to track fuel at every fill up. I take a picture of the pump at fill up just as a record of what is happening. But my sense is that owners are padding their profits with regular grade fuel in premium tanks. It is hard to prove and for the most part unless you truly have a high performance car you would never know (I find that there are a lot of people who use premium with some hope that it gives them better mileage, lol).

For the most part the Porsche ECU fault is a pretty good octane tester.

 

Wow, hope you find the fix, Scat!!

ChuckJ

 

So far so good.. Fingers crossed...

 

Based on my experience with a tuned E36 m3 that permitted trace knock, not all 93 octanes are the same, a certain stations premium always resulted in trace knock at lower engine loads. Unfortunately with my current cars, trace knock is not allowed so I have no idea what I'm getting.

 

With nearly 310K miles on my Boxster, and over 152K miles on my 996 Turbo (I won't include the miles I covered in my GTO, and other cars prior to my Porsches) at an average of 22.5mpg that works out to 20,533 gallons of gasoline and at say 15 gallons per fill up that's 1,368 fill ups -- from various stations from, well from a number of stations located in every state west of the Mississippi and a few east of the Mississippi and not once have I encountered bad gasoline.

While this doesn't necessarily mean you didn't get bad gasoline I think it unlikely.

You really need to read the error codes and this includes the freeze frame data and any pending codes. I suspect something else is going on and it ain't bad gasoline.

 

I agree
All up and down the east coast
46k miles on a 13 4S
Every kind of gas company, gas station.
All the octanes, 87,89,91 and 93.
I don't notice any mpg diff, or hp loss.
Rolling right along...

 

I would agree that scan codes should be reviewed, haven't gotten a chance to connect the Durametric.

However there is little question behind the cause.. it is pretty much cause and effect: A refuel and condition clears immediately.. It has happened more than once.

I'm not sure your experience with a two generation old 996 ECU is much of apple to apples comparison. Glad you are sure fuel wasn't the issue, but your logic experiences aren't particularly compelling evidence for the conclusion you suggest.. By your logic, since I've lived for 50+ without being murdered that must mean no one ever is murdered. What it really means is it is probably rare..

Quite frankly, without the fault indications, I would have never really noticed, so I'm not sure what makes you so confident that you have never had fuel that didn't meet he minimum octane you thought you were buying??

I've had higher compression 60's and early 70's Camero's and corvettes and have had tanks of fuel where the things Knocked under almost no load, so bad gas can indeed be a problem.. I can tell you for damn sure you can't completely trust fuel coming out of a storage tank.. every time I pre-flight a small piston airplane we take a sample, and at times there can be surprising amount of water in it..

But you are right, the scan codes would be useful..

 

Well there's positive proof.. now I can rest easy

 

Lol...