RE my 99 Buick Park Ave 3.8... I stopped for gas. Upon pulling back onto the highway, the car suddenly started to jerk and intermittently stall out, but would restart immediately. After inspecting the engine I found the vaccuum hose that leads to the EVAP canister was broken and could hear it sucking air. I replaced the vaccuum hose assembly, but the symptoms remain. No codes are showing up. I had a mechanic replace the Crankshaft Position Sensor, but still the symptoms remain and he has no further ideas. Intermittent stalling, jerky accelleration, rough idle. Any ideas what to check next?

 

Only going by the info put forth so far,,,,,,,,,,,,,,

It is reasonably safe to assume the fuel tank level was low because that is why you stopped for fuel..
It could be , that there might be moisture, water , in the tank that got sucked into the fuel filter and fuel system. Possible, yes, probable, yes . Checking the fuel filter on removal to see what comes out would help confirm this . Things like this do happen for other possible reasons, but always a good move to check the simple things first.

 

Going on your moisture theory, I added a bottle of Heet to the 8 gallons of gas left in the tank and let it idle an hour or so. It ran crappy, was bucking constantly on the road, and stalled a few times. I added another bottle, let it idle awhile and now it only jerked once during a two mile road test and never stalled.... I believe your moisture idea is valid. If the problems persist into tomorrow, I plan to check the fuel filter. Thanks!

 

Thanks for the update !
Sometimes we get lucky.

 

Hanky is spot on. Yes water can get into those underground containers. Has happened at least twice here in rural ME at the MA&PA type stores.

 

That never occurred to me. We have had some immense downpours here recently in central VA. I will hate to quit using this gas station, they have really cheap gas!

 

Maybe a little background might help.

There are company owned stations and privately owned stations.
Most well known brands have mostly company owned stations although there are a few privately owned selling well known brands.
Privately owned can sell what ever brand will sign up with them.
I can tell you from experience, company owned stations require their delivery people to stick any tanks before delivery for 2 reasons .
The first is to put "theifing paste on the dipstick to determine if there is any water in the tank. If water is discovered the driver reports it to the delivery dept and the co dispatches a truck to remove the water and determine why it is getting in and correct the problem.
The other reason is to make sure there is adequate room in the underground tank for the requested delivery.
Off brand stations to my knowledge are not as strict in this regard. That doesn't mean cheaper stations with off brand gasoline are not as good.
So,,,,,,,some stations have filters for fuel before it is dispensed some do not. That is why when we see a truck making a delivery we wait because it is stirring up what may be in the underground tank and if not filtered we bought it. Unleaded fuel will hold water mixed in it for quite a while before it will settle out to the bottom.
So,,,,, also it can settle in your vehicle's tank too. That is why we usually change our vehicle's fuel filter before winter settles in , AND back that up with a bottle or two of dry gas. Those of us that reside in a cold climate do this without even thinking, don't we Rich ? Thanks for reading some guy's long winded post.

 

Thanks Hanky on that explanation, didn’t realize myself. Where I worked had a fuel farm no less. Jet fuel up to JP8 level but that was almost a decade back. Was always working on those Scullys and then the hazardous spill alarm......

One time a sheet of ice slid off a roof and opened the handle on a ball valve at the pump station. No lock out on it- nothing. So fuel leaked out on the ground all that weekend. Alarm never detected anything as that though, though it was criminal mischief and NCIS shows up, hmm. Not so, had same thing happen at home with a water faucet, imagine. The entire area contaminated; duck pond, stream, all low areas and more...... see if I can locate actual photo of place.

 

Without providing any names, a storage tank with a floating roof developed a problem with loads of water getting into the gasoline. That contaminated gas was delivered to many stations on a turnpike and there were numerous breakdowns and complaints. The company that had the contract paid for all the repairs, towing and new gasoline incurred. As you stated Rich, some things just get by and , well the stuff just hits the fan. We could probably cite many more stories, but sometimes we just like to forget them.

 

Been vacationing in Williamsburg, now it's back to work on the Park Ave. So far, I have been under the car and the gas tank has "non-removable" stamped on it. The exhaust pipe cover welded onto the frame and prevents removal. So, I removed the fuel pump located under a trap door in the trunk, and syphoned all the gas from the tank which was milky white toward the bottom. Now I plan to sop up the remaining gas with a sponge, pour in some 91% rubbing alcohol and clean that out the best I can. Then I will change the filter and gas with a bottle of Heet. Will let you guys know how all that turns out. Thanks!