I have exactly the same symptoms as Steve. Except my idle is ok.

I even noticed how it varies depending on the level of gas in the tank, too!

Perhaps there is some crud in the tank - that becomes more concentrated as
the level decreases - thus affecting - hmmm - the fuel filter?

Thoughts anybody?

Marshall Ruskin
84 Westy

>My '88 Westfalia has been running poorly lately.  Frequently,
>when I press the accelerator, the RPM's don't go up.  Even if
>I press it all the way to the floor, the engine doesn't go any
>faster, and it sounds kind of like it's running out of gas.  Often
>(but not always), if I release the accelerator pedal and push it
>again, the engine speed will surge up.  Sometimes it takes three
>or four repeats of this to get the engine speed up.  The surge
>is often a bit delayed - that is, it doesn't track smoothly with my
>pressing of the pedal, but instead follows a second or two behind
>what it should.  At idle, the van tends to sound like it's going to die,
>but it never has.  My gas mileage is down to about 10 MPG.
>(Usually I get about 15; I thought I used to get better than that a
>year or so ago.)  A couple of weeks ago, the problem would get
>much worse as the gas tank got emptier - seldom a problem when
>the tank was full, lots of problems by the time it reached 1/4.  That's
>less true than it used to be, though - now I have problems when the
>tank is full, too.
>
>My Westy likes fuel injector cleaner, so I ran a bottle through
>one tank of gas.  Possibly some small improvement, but not much.
>
>"Water in the gas", I thought, grasping at straws, so I ran a bottle
>of "get the water out of your gas" stuff through one tank of gas.
>No improvement.
>
>Marvel Mystery Oil has been touted on the list lately as snake oil
>that actually works, so I figured I'd give it a try.  I put 6 ounces in
>a tank of gas, and... all my problems went away.  The van ran great.
>The gas mileage went back up.  Marvelous!  Mysterious!
>
>But...  despite the improved gas mileage, I did eventually use up that
>tank of gas, and filled up again, this time without the Mystery Oil.
>And all the symptoms came back, exactly as they had been before.
>
>I used up that tank (which didn't take long), and tried a new tank full
>from the same gas station, with the Mystery Oil again.  And the van
>runs perfectly.
>
>So, the Mystery Oil sure is great stuff.  Next I plan to add it to the
>windshield washer fluid (increases wiper speed by 50%) and the
>drinking water tank (prevents algae buildup; cures acid indigestion).
>
>But it appears that I'm treating a symptom, rather than the cause.
>Tempting as it is to just keep putting 50 cents worth of Mystery
>Oil in the gas, it sounds like something needs fixing.
>
>Any ideas what's really wrong with my engine?
>
>Thanks in advance.
>
>                                                       -Steven Sittser
>