Think I got a bad tank of gas, what else could it be?

1982 911 Targa · 02-15-2008, 11:24 AM

Have 82 911 sc and i filled it up last night with 91 octane from a cheaper place but I have been going to same gas station for awhile. Drove it for about 10-15 minutes and parked it. Ran perfect, then when I went to start it, it started idling around 200-300 instead of the normal 900-1k, It never actually died but it is popping and backfiring every once and awhile. I can also smell gas from it, like not all the gas is getting combusted in the chamber. It has a complete lack of power and wont accelerate. Everyonce and awhile it sounds perfect and drives normal then it goes back to this. Im thinking I got some bad gas and everytime it gets a grab of the good gas that was in the tank it runs good for a little bit then it gets more bad gas, now the gas has sat and mixed and it sounds bad all the time now. It doesnt sound like it lost a cylinder and all the plugs and wires are good. I am 80% sure its got something to do with the fuel, but people here know way more then me.

What else could be the problem, or how do i go about fixing the problem? THANKS everyone. -david ps: was going to sell it today but had to call and say something happened to it. ****

Bill Douglas · 02-15-2008, 11:40 AM

An easy thing to check first would be to see if the pop-off valve in the airbox has stuck open.

1982 911 Targa · 02-15-2008, 11:51 AM

its closed

Paulporsche · 02-15-2008, 12:11 PM

Check to see your gas and oil caps are on tight and that you don't have a vacuum leak, say @ a connection for a vac line.

joecrum · 02-15-2008, 12:38 PM

I'm quite sure the "bad" gas would have throughly mixed with the "good" gas as it was being pumped into the tank. The exception being that which was already in the lines.

Look carefully in the engine compartment for anything that may have come loose (dist/plug wires, vacuum lines, etc). Does your fuel pump sound louder?

Good luck!!

Richard Burns · Richard Burns's Garage

It could be that your fuel filter is almost blocked. It will let a small amount of fuel through but you can't get full acceleration.Take the filter off and empty it that will move some of the blockage refit it and see if there is any difference.

Zeke · 02-15-2008, 01:32 PM

Look for water in the bottom of the tank after the car sits for a spell. Do this by removing the sending unit and inspecting with a match. No, I was just kidding, of course. Use a very bight LED type flashlight or a VB penlight. If the water bubbles aren't hiding, they will glisten. You can move the car to move the gas to see if any come out from under a baffle. Depends a lot on the angle the car is parked.

It's a good idea to inspect the dirtiness of a tank now and then anyway. If you have water, you can treat a small amount and change the filter. If there's more than just a small amount, siphon the tank dry (safely), refill with good gas and treat for any water left in the fuel system. Change the filter again if you have to if it's a paper type (I guess they all are anymore, but I'm not totally sure). The paper does sop up the water, but it messes up the filter.

After you know all is well, buy a new cork gasket for the sending unit as it will most likely leak enough to produce a smell in the trunk after being compressed once.

1982 911 Targa · 02-15-2008, 01:41 PM

good news is it seems alot better now, i bought some fuel additive to clean everything, it kept doing it and then was told i needed to run it hard and get it flowing through the system quickly to remove any restricted paths. I also added some water remover stuff and put that in just in case there was a little condensation. Ran it hard and it doesnt seem to have any of the problems anymore. Thank you know who, that that was easy. *knock on wood* Ill let the water stuff sit overnight and maybe it will be back to 100%, still doesnt feel quite as strong as it was. Thanks for your comments.

Trotskyite · 02-15-2008, 01:42 PM

Does it smell really rich? If so, check to see that the WUR is firmly plugged in.

teenerted1 · 02-15-2008, 01:50 PM

when was the last time the fuel filter was replaced????
probably time to replace it anyway.

sounds exactly like what happened to me last fall

swapped plugs was better for a few miles then the same symtoms came back after an italian tuneup. was going to swap out the pump but tried the filter first...

BINGO. new $3 filter and problem solved been problem free for 4months now.
was one of the few things the PO and mechanic didnt change when they did rebuild last year.
your results may vary.

bell · bell's Garage

Quote:

Originally Posted by teenerted1

when was the last time the fuel filter was replaced????
probably time to replace it anyway.

sounds exactly like what happened to me last fall

swapped plugs was better for a few miles then the same symtoms came back after an italian tuneup. was going to swap out the pump but tried the filter first...

BINGO. new $3 filter and problem solved been problem free for 4months now.
was one of the few things the PO and mechanic didnt change when they did rebuild last year.
your results may vary.

my money is on the filter, sometimes at older gas stations their filter systems from the tank aren't working great......and if you showed up a little bit after the tanker did (when it filled their tanks) then the tanks were stirred pretty good by the entering fuel and could've sent the crap or whatever into your tank.....happened to me twice with 2 different cars......

1982 911 Targa · 02-16-2008, 08:14 AM

ya problem is bak this morning. I replaced the fuel filter about 3 months ago so think i might do that again since it is cheap and fairly easy to do. Dropped by a mechanic and he looked at it and said try some injector cleaner through the system and it sounded ok.. OF COURSE it sounded fine when i was there and as soon as i got back home it started up again. will get filter today.

DanielDudley · 02-16-2008, 08:35 AM

Quote:

Originally Posted by 1982 911 Targa

ya problem is bak this morning. I replaced the fuel filter about 3 months ago so think i might do that again since it is cheap and fairly easy to do. Dropped by a mechanic and he looked at it and said try some injector cleaner through the system and it sounded ok.. OF COURSE it sounded fine when i was there and as soon as i got back home it started up again. will get filter today.

Could be water, but check your plug wires as well. Often fuel problems turn out to be ignition related, but in your case it could very well be bad gas.