Gene K

This look like a bad tank of gas to anyone? My cars trap speed has suddenly plummeted despite better air.

http://i253.photobucket.com/albums/h...sonBadFuel.jpg

Im hoping I just got a bad tank of gas and its pulling timing on the top end.

AmericanSpeed

Could be bad gas. I had a tank that was making my car idle rough, after new tank, it ran fine. How many times did you trap this lowand in what time span? I've had a few random runs where I may have shifted at the wrong rpms or something that caused my trap to be slightly lower. If it is not consistent, I wouldn't worry about it too much.

Gene K

That was the fastest trap out of 6 runs Sunday (Worst was 105.3).
The car had no symptoms other than being a tenth and 1.5-2.0 mph off the pace.
Their is no miss (plugs) or flattening of power like fuel pressure drop or vavlesprings.
Im guessing if its pulling timing starting in the midrange when cylinder pressure starts to ramp up I wouldnt feel it.

Im thinking that maybe I got a tank of 87 instead of the 93 I paid for. No audible knocking but I suspect the knock sensor would pull timing long before I heard it. The 330' looks about right for the 60' but from their you can tell by the 1/8 mph and then 1/4 mph its down on power.

haproot

Yeah thats what I would think. I know that it seems that 1 of 2 things will affect my performace.

1. Barometric air pressure

2. Gas

It seems when we have a low pressure, ie: cloudy stormy day. (and I do live at hight altitude) my car seems a bit slower for that day. I've datalogged when my car feels sluggish and if I read the current air pressure it's lower than normal. Also gas but I usually go to the same place for my gas every fill up. The only give us 91.. The humanity!

67mustang302

Drain a bit of gas and smell it. If it's bad it'll smell bad. Also consider the fuel truck jockey may have pumped lower octane fuel into the wrong tank, either by error or just plain laziness.