: bad gas?



s4ologist
09-29-09, 08:45 PM
I think/hope that I just have a tank of bad gas...

I recently filled my tank up at a place that was closing down all of the 91 and 93 octane pumps ... except one (I know, I should have taken that as a red flag). During my fill up with what was labeled as 93 octane, the attendant walks up and puts "out of order" stickers on the 91 and 93 octane pumps at the station I was using, saying that she was surprised it was working. Anyway, shortly after getting that tank, my car started acting up. It is now rough at idle, and seems to "hiccup" frequently, especially after warming up. Attempts to go WOT or even close make the loss of power and hiccupping much more rapid (I don't hear a "ping" or "tick" sound, but I wonder if this is predetonation).

I put two octane boosts into the fuel, which has not changed anything so far. I guess I will drive easy until this tank is almost out, then refill with what hopefully is 93 octane.

Am I on the right track, here, or could this be a bad spark plug or something else. All I have done to the car so far is Hennessey intake, AR Headers, and a tune (4 K miles ago, and it has run well until now).

nynd
09-29-09, 08:58 PM
Maybe water in the gas especially if the tank was running low at the pump station? If you think the gas was bad, suction it out and go and refill from a know service station.

Gary Wells
09-29-09, 09:19 PM
Just as nynd said, except you might want to try a couple or 3 cans of that heet evaporator for water in gas, and if that does not work, I would be suctioning that stuff out in a hurry. HTH. Also, 10 points of octane booster equals only 1 octane # so I would try some unleaded high octane and see if that doesn't help. In Kali, you can get as high as 105 unleaded as select pumps. Mot free, but neither is your motor.

Looney100
09-30-09, 09:16 PM
Not sure if it is bad gas, but just take it easy on the accellerator until you get through the tank and refill at some reputable station.

A couple corrections to some of the previous posts, though. 10 points of octane boost is only 1/10 of an octane #. i.e. it will take you from 87 octane to 87.1 octane. I recently read the labels on a bottle of octane booster. The front label said it increased octane by 10 points. The fine print said that it only worked in 87 octane gasoline, and that 10 points was 1/10 of a number.

Also, water is heavier than gasoline, and therefore always resides on the bottom of the tank. Having a tank near-empty at a service station won't, on its own, result in any increased water content in the fuel.

SlvrBullIT
09-30-09, 10:50 PM
Not sure if it is bad gas, but just take it easy on the accellerator until you get through the tank and refill at some reputable station.

A couple corrections to some of the previous posts, though. 10 points of octane boost is only 1/10 of an octane #. i.e. it will take you from 87 octane to 87.1 octane. I recently read the labels on a bottle of octane booster. The front label said it increased octane by 10 points. The fine print said that it only worked in 87 octane gasoline, and that 10 points was 1/10 of a number.

Also, water is heavier than gasoline, and therefore always resides on the bottom of the tank. Having a tank near-empty at a service station won't, on its own, result in any increased water content in the fuel.

But the gas station pumps from the bottom of their tank..... Hence don't fill up at a station that is due to receive their gas and shortly there after due to sediment disturbance.

qictrk
09-30-09, 11:10 PM
It sounds like its the gas. If it was running ok before you went in and gave trouble afterward, guess what. They were putting the signs out there for a reason. They should have told you to get gas elseware until they got their station up to par. I would try to get all the gas out of the tank before it does some possible serious damage. Cecil..........

s4ologist
10-01-09, 03:10 PM
UPDATE:

I added HEET without a change, so it wasn't water (it was worth a $2 try, though). Since the symptoms only really kick in when I accelerate moderately to aggressively, I went easy on it until that tank was near empty, then refilled with 93 at another station. I'm almost 1/4 through that tank with absolutely no change.

Now I'm going into "wild speculation" mode. Could an injector be (partly) clogged? Spark plug misfiring or other electrical issue?

Could the tune that I had done on the dyno have worked well for a while (great for the last 4K miles), but now somehow be too aggressive (different gas quality, possibly seasonally related). But I'm not even sure this is "knock"/predetonation. It just sounds like it's cutting out (little blips of silence associated with power loss) and shuddering when I hit the gas. If I'm in 1st or 2nd, I can accelerate moderately without issue, although it is a bit hesitant. The cutting out occurs with greater frequency with increased load (higher gears and increased throttle). Another thing. Does "oxygenated gas" use change seasonally (maybe San Antonio is getting different gas this time of year)? Would that affect engine performance enough to have these symptoms?

I have no clue, so I'm taking it to the dealer on Saturday morning (needs an oil change anyway). All I have is intake and exhaust, so hopefully no problems there.

Thanks for the input.

Gary Wells
10-01-09, 04:22 PM
I had the same symptons years back with a non-fuel-injected car (Boss 351)
from a similar situation (pumped gas from bottom of tane) and it turned out to be a fuel filter, both in-line & at carb). Maybe a fuel filter and / or fuel injector?

Looney100
10-03-09, 03:23 PM
But the gas station pumps from the bottom of their tank..... Hence don't fill up at a station that is due to receive their gas and shortly there after due to sediment disturbance.

There is no harm in filling up when a station's tank is nearly empty. You're right that sediment and water can get stirred up after a delivery, but water in tankage is fairly rare and there are filters at pumps that will take out any sediment before it enters a vehicle's tank.
Either way, unless you see the fuel truck delivering gas when you arrive at a station, its impossible to know when tanks are being refilled, so don't worry about it.

The best advice I can give is to buy from a station that has steady traffic, and is wearing a major brand.

Gary Wells
10-03-09, 03:53 PM
There is no harm in filling up when a station's tank is nearly empty. You're right that sediment and water can get stirred up after a delivery, but water in tankage is fairly rare and there are filters at pumps that will take out any sediment before it enters a vehicle's tank.
Either way, unless you see the fuel truck delivering gas when you arrive at a station, its impossible to know when tanks are being refilled, so don't worry about it.

The best advice I can give is to buy from a station that has steady traffic, and is wearing a major brand.

Your statement regarding filling up when a station's tank is nearly empty might be true today, but it wasn't years back. What happened to me happened in about '83, maybe '84, but it did happen. It was also not a name brand station.

09V
10-03-09, 06:11 PM
S4ologist,
have you resolved your issues? I also live in San Antonio, who do you use for service? Do they have any issues with your mods? I would venture to say that if they fail to help you out you may have to put it back on a WB02 and see what its doing.

s4ologist
10-04-09, 12:07 AM
Issue Resolved:

I took the car to Ken Batchelor Cadillac, and they found engine misfire codes, and that the 5th spark plug wire was disconnected (I had no CEL, btw). They charged me $79 for a diagnostic fee, claiming that the installation of headers requires disconnecting the spark plug wires, and was the likely cause. I offered only minimal protest: The headers were installed 5K miles ago. Since it was only $79 (they didn't charge me for labor), I didn't pursue it in the interest of having a friendly relationship with them. Besides, I can't prove their claim false (maybe it was loose after the install, I don't know).

This experience doesn't really shed to much light on the warranty issue as a whole, though. I mean, if a supercharger fails on a car with no pulley swap, just intake and exhaust, or if a head gasket is blown, what would happen then? Honestly, I don't want to know.

The car runs perfectly now, and I guess I could have checked the plugs myself (the ones toward the back look a bit hard to get to, and I would have spent some time checking all 8 plugs, but now I know what a disconnected plug feels like), but I'm just happy it's done, and not a big deal.

What I wonder is: if a plug isn't firing, but fuel is still being sprayed into the cylinder, could hydrolock occur (was I dang lucky that it didn't)? It felt to me like it was firing intermittenty, anyway.

Thanks for your input on this.

GMX322V S/C
10-04-09, 04:08 AM
What I wonder is: if a plug isn't firing, but fuel is still being sprayed into the cylinder, could hydrolock occurNo; the fuel is still being atomized, hence compressible along with the air being drawn in. About the only things you run the risk of are leaching the oil film from the cylinder wall and heating up the cat(s).

SlvrBullIT
10-04-09, 06:39 AM
My V was purchased at Cavender in San Antonio but originally it was shipped to Covert in Austin. When I test drove it a CEL was thrown and it was very harsh sounding, apparently a bad spark plug was the issue, so maybe bad plugs is an issue. If you did a dyno tune and was fine then how the heck does a plug wire come loose 4K miles later????? I think a plug went bad and they just said it was a loose wire to get $79 from you.

SlvrBullIT
10-04-09, 06:40 AM
I'd do a couple of spirited runs to clean some carbon from the #8 cylinder...... hehe

komar
10-04-09, 02:28 PM
if you think you have bad gas immediately drain the tank. Octane booster from walmart will not work. if you are not able to drain the bad fuel, go to a local speed shop, get a few (Less than 5) gallons of highest unleaded race fuel to cut the "bad" gas that's still in the car. then fill up the car with good fuel from a trusted station, and if needed change your fuel filter if still having problems.