zumaron

I filled up and drove on the freeway for about 15 miles and exited with no issues. After pulling away from the traffic signal the engine started misfiring @ 3K RPM's as if it was running out of gas. The engine idle was normal and rev'd smoothly in neutral. However, under load the car would hesitate, surge, lunge, etc while accelerating. The check engine light did not come on.

The service dept. was closed so my first stop was rennlist forum and my search turned up a few threads on misfire & bad gas, which suggested trips to the dealer with no clear resolution. I then contacted a knowledgeable salesperson (they do exist) and we discussed potential causes and solutions. He thought there could be a pressure equalization issue with the gas tank / fuel lines and suggested the following:

1. turn engine off
2. open gas cap
3. start engine and run for few minutes
4. put gas cap back on

I'm happy to report this worked! Hopefully this will save someone else the agony and frustration should this same problem happen to you.

EDIT: The problem came back again 300 miles later. I went for a drive with the service manager and fortunately it was still misfiring. The service tech and manager did another 5 minute test drive when they came back it was running smoothly after they "opened it up".

They think it's due to bad gas or a particle in the fuel system inhibiting the flow and suggested I drive it hard to keep it cleared out and don't use that gas station again.

I'm not convinced yet.

Links to similar symptoms:
https://rennlist.com/forums/997-forum/235679-check-engine-return-to-workshop-she-s-home.html
https://rennlist.com/forums/997-forum/241365-help-something-is-wrong-with-my-car.html
https://rennlist.com/forums/997-forum/175369-warning-about-gas-quality.html
https://rennlist.com/forums/997-forum/238662-check-engine-light-triggered-twice-now.html

wardo

Great info....thanks

drbf

Thanks for the heads up. I had a similar problem and found water in my gas tank.

Coochas

Zuma...
I think what your dealer described is what is referred to as "vapor lock." It's usually more of a problem on hot days but I didn't realize it still happens with today's designs of gas tanks and tank caps.

And Ben,...I will refrain from saying that I have had bad gas in my 997 too.

gota911

Dave - considering a couple of your recent quotes, "Cayman my ***" and "bad gas".... there could be a connection there!

Coochas

OK, flag on the play (or is it *** on the play?).

Deven

I posted a similar incident a couple of weeks back. Was going to take it in but has not happened since, and it seem sto be a 'common' phenomenon with explanation sometimes:
https://rennlist.com/forums/997-forum/262872-car-fluttering-today.html

also another thread on rennteam:http://www.rennteam.com/showflat.php...885#Post211369

OCBen

And that connection must be Dave's exhaust pipe.

zumaron

Back in the good 'ol days of high school my volkswagon would vapour lock on hot days. It had a mechanical fuel pump that was on top of the crankcase and carburetor which was prone to vapour lock. I'd put ice cubes on it to cool it down -- probably didn't make a difference though.

I suspect it's something else with the 997 since the problem is occuring in varying climates. In addition, my car sat overnight and in the morning the symptoms still existed (low 40's). The good news is I didn't have to take it to the dealer.

Thanks for the additional info. Fluttering wasn't one of the search terms I used, which is most likely why I didn't see your thread. :-/

blk on blk

Guys this is happening to my 996 at the moment too, and I think it is bad gas. Actually I think it is "summer gas" that mixes in some different additives and is not as efficient or pure as the gas that is refined in the colder months. I have almost run the tank dry. I am going to run some techron additive through it, and use a different station for gasoline and see if that helps. I have about 3k miles too.

kocsis

Any suggestion for stations with "good gas"? I recently saw a posting of high quality gasoline companies...is that an accurate list? It doesn't include Mobil, which i thought had very good gasoline.

blk on blk

The one that I currently have that I believe is "bad" is Chevron which normally is a very good gasoline.