Bad gas or something else?
 

A national gas station chain started carrying 94 octane in Alberta. Previously 91 was the highest available in this area. So naturally, I filled up. Ten or 15 minutes later I was experiencing rough idle, reduced power and an odd 'air' or puffing kind of sound from the exhaust every few seconds. It would just do a sort of "puh" and then a few seconds later, another one, and so on.

I suppose it could be something other than gas, but I don't know what to check off the top of my head. It was running great before the fill, and after, not so much. It would be really coincidental if it wasn't gas related, but I want to cover all my bases.

Any suggestions on what to look at?

This is on my '87 Carrera BTW.

If you have a Weights and Measures organization that is in charge of fuel quality, give them a call. They will test both the gas in your tank and and the tank at the station.

I would pull your fuel filter and empty it into a clear container and look to see if the fuel separates into a fuel/water mix.

Higher octane won't do anything for your car. High octane simply means it is harder to get it to spontaneously light off. This allows greater ignition advance and/or higher compression.
Newer cars with knock sensors can see improved performance from higher octane because their ECU can increase the ignition timing on the fly to get the most out of it.

As to why you would see an immediate problem. Only two things come to mind...
- They sell less of the 94 octane so there is more of a possibility that water or other contaminates could build up giving you a bad tank of gas.
- It is a coincidence and you have another issue causing the problem.

Higher octane actually might be good. I have a RoW car with the 10.3:1 compression and it's chipped. Summer and higher temps are on the way up here so that little cushion is good for some piece of mInd. The altitude is pretty high here so that helps and normally the 91 is good enough, though detonation is not always audible. I know I'm not going to get more power with 94, but that bit of extra safety in a high compression single plug engine when the temps get up to the 95F area makes me feel better.

And yes, I realize it's either bad gas or something else, but I was hoping someone would point towards something that might cause this (other than gas) or have similar symptoms.

the puffing sound you described sounds like a pulled head stud

Wouldn't that happen all the time, though and not just every few seconds? And would that cause the rough idle? Crap. I was thinking of doing a valve adjustment anyway so I can check that easily enough, I just don't want to HAVE to do it now...

I'll check the fuel filter first and look at things like exhaust studs. I called the weights and measures people to get the gas checked, but they will take up to 14 days.

BTDT. Seen this more than you would think. I'll cast my lot with Joe Bob and say contaminated fuel. Water or diesel. If your car is running at all it wasn't much.

Hopefully this works out with a drain and fill and purge of the fuel lines. If this turns south and gets expensive think about contacting your insurance. At least in the states that would ba a coverable loss. Ins Co can sometimes help you put the screws to the station that sold the bad gas. If it got your car it likely got some others. In a small town you can ask around. Big city not so much.

J

I had a bad tank of gas once. Filled up, hit the freeway on ramp and it fell flat on it's face.

I was an inspector that had that station on my caseload. I called up their enviro dept.....I didn't identify myself by full name, told them what happened and they took care of me......they shut down the tank in question and found significant contaminants. I later told them who I was after I told my boss so that there was no feeling that I was shaking them down.

They paid for the filter, 2 hours labor @60/hr and two tanks of free gas. I did the repair.....because I had already done it prior to their offer.

Kev,
Here's another possibility. I have a 76 so we have different fuel delivery systems, so perhaps my experience is not relevant to yours. When I recently filled up at the local farm supply where I can get 93 octane no ethanol gas I noticed that the engine appeared to be running rich, as if I had messed with the fuel mixture screw. It ran rough and would not idle properly. The idle was hunting as if the mixture were too rich. My conclusion is that the non-ethanol fuel, because it contains all hydrocarbons and no oxygen containing compounds, was producing a richer mixture. When I switched back to the 91 octane ethanol mix, which is much more readily available here, the problems disappeared. Both ethanol and MTBE, the favorite contaminants added here in the USA, are intended to supply extra oxygen to the combustion process. By doing so they require a less rich mixture setting on the fuel delivery system to give a proper fuel/air mix. As I say, with your automated DME system, my observations may not be applicable to your car, but perhaps your problem is simply temporary, fuel composition related and not due to water in your fuel.

Thanks Joe Bob. Call already in to the chain and an inquiry or something in progress.

Targa, it's likely not an ethanol issue. I always fill up with non-ethanol (it is available in the premium blends in western Canada) so that shouldn't be the issue. Nor did I have problems with your gas in WA and OR states. However I don't know for sure if this 94 octane stuff is ethanol or not. I just made the assumption that it was based on my experience with other retailers unusually use.

Thankfully I had a half tank already or perhaps it wouldn't even run on a full load that other stuff. Assuming it IS the gas that's the problem. Can't wait to get home and pull my filter.

My Guess, there is a cross cantamination of either Diesel or water.
Seen it when a local station had just had a delivery, my partners father put some fuel in [thankfully it was only a small amount] and within a few hundred yards the car would hardly run!
Anyway, i removed the fuel pump feed and drew out some of the fuel into a glass bottle, sure enough, within a few minuits there was seperation, turned out, the tanker driver had filled one of the petrol tanks with Diesel!
Lots of angry motorists that day.
A...

I ran some of this 94 ocane in the 930 and experienced no issues.

Yeah, different stations and all that. Probably just crud or water or diesel mixed in there. Are all the petro cans carrying it down there? I only know of the one on Shaganappi by Market mall for sure.

Problem seems to be solved. It's quite difficult to find a place where I can drain my gas. No body wanted to take it so I had a shop drain it and put in a jerry can of fresh stuff this morning. Now I just have to change my fuel filter. Sounds like a good after work project tonight.

The thing that put "gas issue" at the top of my list was a funky, kinda solvent smell of the exhaust. It wasn't a rich running smell, at all. It was almost mediciny if that makes sense. I still checked some other possibles such as the cap and rotor, plug wires being disconnected, etc. After the old gas was gone and fresh stuff poured in, the car idled normally after only a couple minutes.

+1 on got a bad tank of gas once from me. Swear my car was running perfect, filled up, parked, and next day was terrible idle and poor power. I drained some and burned the rest. I am 2 tanks of fresh Vpower away from that now and it purrs like a kitten. Had to be the gas. I have since banned that gas station from my stop list.

If you have a lawn mower....mix it in with the normal fuel. I should burn alright....or bring it to the retailer and sk them to dispose of the crap they sold you.

Uhhh, yeah...

Retailer (this morning): "I just called to let you know we completed our investigation you initiated on Monday. You should be happy to know that after testing, we have found that there is absolutely nothing wrong with the gas. You can continue to use it without any concerns."

After telling this person that I just drained the tank it it now runs great again, she just reiterated that the gas is fine and that it must have been condensation in the tank that was causing my issue. There were no other complaints, blah, blah, blah and so on...

With the odd odour of the exhaust, I suspect it wasn't water, either. But it's done now and I'm a little bit wiser.

I have a small lawn so my mower is beer powered. :D I should have just called up some friends to see if any wanted some free gas for their yard machinery and stuff.

Are you suggesting MY tank wasn't drained or the station's? Mine certainly was. I didn't say that the station's was, either. They claimed there was nothing wrong with their gas. Maybe you can pass around what you've got...? :)

IIRC, Sunoco Gold 94 (I'm assuming that's what you were using?) found at PetroCan is an E10 blend...

Yep, PetroCan. The gas here from them is refined locally in Edmonton, though. You easterners get much or yours from the US. However, that's not to say it's still not an E10 blend. I didn't specifically check or ask, and just assumed it wasn't, as the other retailers that I purchase from specifically post that their premium (either 91 at Shell or 94 at Chevron in BC) is not an ethanol blend. In the past when I've been in the US, the local dinosaur juice has been ethanol with no issues experienced.