For the last few cold starts I've noticed a very sharp intermitent misfire that goes away after a few minutes. Has anyone else had this issue and if so what's the cause and resolution? It could be a bad tank of gas as yesterday I filled up (Chevron 93).
350 miles on odo and in warm cimate.

Thanks,

 

I dont think your going to get too many to agree that Chevron 93 is bad gas...
That doesn't exclude the possibility of a bad storage tank (water seepage or whatever) from the station itself.

Winter fuel mixes (Oxygenated or with Nitrogen) can have reduced BTU output, but not enough to cause a misfire.

Lexus did an interesting thing that maybe Jag is doing as well. On cold starts, they run rich, and open the exhaust valves slightly early. This lets unburnt fuel travel down the exhaust manifold and heat the catalytic converter up very rapidly, kinda like an afterburner (Converters don't start working until they are up to temp.). In a very short time the cats heat up and the valve timing is dialed back to a more normal setting.

Not saying that is whats happening with yours, but it was interesting to see how Lexus brought emissions under control very quickly with this process, and any time you have flame outside the combustion chamber it may produce a popping sound.



Vince

Others here probably have a better idea for you... I'm just tossing ideas...

 

Thanks Vince.

I wasn't saying Chevron as a whole was bad gas but the tankful I just got may have been.

The car always idled smoothly during cold starts until yesterday and the fill up, so I'm hoping it is a bad tank of gas.

350 miles on the odo and in warm climate.

 

You might consider adding a water emulsifier (STP fuel treatment) to your tank.

Could be you got some water by sucking gas off the bottom of the storage tank (water separates to the bottom), or maybe a fuel truck was just there and filled the storage tank, which tends to remix separated water for several hours before it resettles again.
(Usually if I see a tanker truck refilling a station, I drive on by and fuel up later.)

The fuel treatment should specify water removal, because I think you can get injector cleaners that do not have the ability to emulsify water.

Just tossin more out there for thought...
Vince

 

Slightly confused.

The car only has 350 miles, this must have been your first top up on a brand new car.

Contact your dealer forthwith, and explain your concerns, they are obliged to keep you happy.

Please keep us posted.

 

Thanks guys.

Vince, I'm almost at a quarter tank now, should I just burn it all off and see what happens with a new tankful, or add the treatment now?

Richard, this is my second fill up. I'm only avg 11 mpg. Car now has 427 miles to be exact.

 

I'd head back to the dealer before adding any treatments, you don't want to have any problems if it turns into a warranty claim.

 

I can't argue with the dealership recommendation and it is easily your best first choice.

If you did get water in your last fill-up, an emulsifier is harmless to your fuel system. Its only purpose is to force water in the tank to become suspended with the fuel so it can be consumed, rather than remaining in the tank.

I would add the required amount to a fresh fill-up. Remember if it is water, it is pooling at the bottom of your tank, so even at 1/4 you could have a significant amount in there.

If the problem was not water, no harm, no foul.

Look on the bright side. We had a 76 station here that had diesel dumped in the regular storage tank. Everyone filled up and got three blocks away before they consumed the gas that was in the fuel lines and the cars stared dying! That one set the station and insurance company back a pretty penny or two!

V

 

Here in michigan, the winter gas has been horrible this year. We are getting 2-3 cars a day for stumbling, starting and stallings, and misfires codes when cold start. And it has mostly been because of the oxygenated and high ethenol content in the gas. What we have been having success with is having the customer use an additive from Lucas called ethanol stabilizer.

If you did get water in the gas the emulsifier won't hurt anything.

 

Norm, no doubt that's the safe bet.

Vince, I may try that to see if it helps. I too avoid stations where the truck is filling the tanks.

Austinmatus, thanks for sharing that, PM sent.

Thanks all.

 

Not particularly apropos, but since it's a gas thread > www.toptiergas.com

 

Good article, thanks for posting.