Hey Everyone,

I recently picked up a well cared for 2002 996tt. It's modified, with the k24 turbos, injectors, bigger intercoolers, etc... It was tuned in Phoenix AZ on a Cobb AP for both 91 octane and Race Gas.

I bought it in AZ and trailered it back to CA. I have owned it for 3 weeks and it has been a dream. Here is my problem.

I filled up at a Chevron down the street that I never fill up at, it's a remote location and I don't see many people using it. Anyways, almost exactly after filling up at that station, I noticed white/blue cloud out of the exhaust when I start the car up, and I get around -6 counts of knock at WOT and the car pulls timing. The car seems to drive just fine under normal driving, but anything aggressive and it ****s the bed. Is it possible I filled up with a bad batch of gas? Or maybe It's bad plugs, ignition coils? MAF?

Anyways, I have 3/4th a tank left, and I really wanted to siphon the gas out instead of burning it off, just incase it is truly bad gas. I've been contemplating accessing the gas tank in front of the battery and siphoning it out that way.

Any helpful ideas would be great, thanks so much!

Doug

 

Congrats Doug! Makes sense for the most probable scenario. No cel?

Since it's 3/4 you can add some additive to help as you burn through it. Keep us posted.

 

Hey Sam!! Thanks man.

That's correct, no CEL. Would you mind suggesting a good additive for me? I'll go pick it up this weekend.

Thanks man.

 

Cheers. hey Chevron likely started the issue, use theirs!

 

Reads like a classic gas of bad gas. Some time ago a fuel test done by a car mag (EVO in the UK) found "bad" gas a real problem. The recommendation was to buy from a busy station to ensure getting the freshest gas possible.

While I have found Chevron gasoline to be a good gasoline -- the Boxster loves it -- the Turbo doesn't react as positively but the engine runs just fine nonetheless --- an out of the way station is just asking for stale gasoline and especially 91 octane as not many cars require this so the fuel can linger a while.

I know of no additive that will unstale (so to speak) stale gasoline. I think the behavior of the engine is such it worth the trouble to remove as much of the gasoline as possible and use it in a less demanding vehicle or save it for the lawnmower.

Then of course add enough fresh premium gasoline to allow the engine to start and run and get the car to a busy station and fill up with fresh 91 octane gasoline. You can try another Chevron station or use Shell, or Union 76 any name brand top tier station. I shy away from the discount gasoline brands.

 

Thanks for the information Macster. Those are good notes on only filling up at busy gas stations instead of the secluded one I chose to fill up at. I'll do that from now on. I'm going to try siphoning the gas tank this afternoon and filling up with 100. I'll let you know how she runs after.

 

as mentioned if you throw a bottle of techron in the tank along with a top off with some 100? you wont have to drain anything.

 

Stale gasoline has lost its ability to combust properly in and in this case in a high compression engine.

The gasoline the OP filled the tank with may be more than stale. The storage tank could have been filled with the wrong gasoline, perhaps 87 octane, and the station may not know this or if it does hope to move the 87 at 91 prices and with no one the wiser.

Besides, Techron does not claim to do anything for stale gasoline. Techron is a detergent/fuel system cleaner.

Adding 100 octane gasoline -- which itself could be stale as 100 octane gasoline doesn't just fly out of the pump due to its hgh cost -- is just a hope that it will help.

I see no reason to put the plugs, valves, O2 sensors, converters, and other parts of the engine exposed to combustion/exhaust gases at risk of damage just to burn up a few dollars worth of stale gasoline.

If stale gasoline is the problem. The reported behavior has the aspects of it. By removing the suspected stale gasoline -- rather than attempting some band-aid solution of questionable value -- one eliminates gasoline as the possible cause and if the engine's behavior doesn't improve after the stale gasoline is removed and replaced with fresh gasoline then one knows gasoline (stale or fresh) is not the cause of the engine's behavior.

 

well,... OK then! lol.

the car doesn't need to be "babied" thru a partial tank of questionable fuel and he's not gonna hurt the car by running thru a semi filled tank esp if he adds some higher octane ( and techron isn't gonna hurt ) but then, you'd probably suggest he change the oil also after adding the techron stuff too which wouldn't be a bad idea either. but whatever, you're the expert

and he said he's gonna drain it anyway..

 

not sure i would call 9.4 to 1 a high compression engine

 

So I was able to drain just about all of the gas out of the tank this morning. I think I may have missed the sleeves of the gas tank that go down on both side. I think there may have been half a gallon of the bad gas still in there. I filled the car up with the 5 gallons of race fuel I had on me, and drove to the gas station and topped her off with 100.

I switched to the race gas tune map at the gas station and sure enough when I turned the car over, there no longer is a huge puff of blue/white smoke out of the exhaust. I drove the car conservatively for 20 miles or so and she felt as normal as expected. I did one brief pull in 2nd gear and my Cobb AP showed -1.5 counts of knock at WOT. This is an improvement over the -6 to -7 counts I was getting with the previous gas.

I'm going to drive the car conservatively for another half tank and top the car off once more with 100 to make sure I've cleared the system of the potential bad gas and hopefully the knock goes away completely.

If I'm still getting 1 count of knock after that, should I start looking into plugs, coils, maf?

Thanks again for everyones help, this community is amazing.

 

I have 3 high volume stations I choose from and always will bypass the station if the tanker is in the process of filling the underground tanks.

 

I'm going to stick to high volume stations from now on jhbrennan Is there an app to show high volume gas stations? If not, we should make one.

 

That puff of blue/white smoke has nothing to do with the gas. It's a 996 turbo and they do that some times. I get it about once every month or so and my car goes 5K miles on 1 qt of oil. The knock sums, probably.

 

lol my car puffs sometimes, like an old TRAIN, if i park on the incline- for 20-30min --- I only trust Shell - that's all.