Mystery Stall..(Cheap Valves?)

[jadney@vwtype3.org (Melissa & Jim)]

>From: "machfive" <machfive@ix.netcom.com>

>Anyway, it's got worse in terms of  sputturing on the freeway.  In fact,
>once on the way to work and a few times on the way home it completely died
>out.  It almost felt like it wasn't getting spark for a few seconds or
>maybe gas.  But now I'm wondering if it could be a result of the horrible
>rebuild.  Another mechanic I took it to said that it needed a valve
>job-that the valves possibly didn't seat right or something.  The weird
>thing is-I kept trying to make the car behave funny, but it would do it
>only once in awhile.  It didn't matter if I was going 5 mph or 55 mph, or
>if I let up on the throttle or if I was giving it gas.  Then the problem
>would stop for awhile and the car would run fine.  

Here's what I would suggest:  You need to narrow the problem down before you 
can attack it.  Intermittent porblems are always the worst, because you will 
almost never actually find a problem if it is not acting up while you're 
looking.  I assume you still have the FI.

So....

1)  You need to find some set of conditions that will produce the symptoms.  
Driving on the freeway is fine.

2)  Check the voltage across the battery while the engine is running well 
above idle.  It should be 14.1-14.4 V; if it is below 13.5 V replace the 
voltage regulator with a genuine Bosch one.

3)  If the car is a squareback, remove the engine cover, attach a fuel 
pressure gauge to the fuel ring and a timing light to one of the plug wires. 
 Then put a friend in the back where he can watch the gauge and the light.  
Drive down the freeway (or whatever) and create the symptoms.  Have your 
friend watch the pressure gauge; if the pressure stays up around 28-31 psi 
it is not a fuel pressure problem.  Have him watch the timing light moving 
to each plug wire in turn; if it flashes steadily on each plug then ignition 
is probably not the problem.  If either of these tests fails, then you need 
to fix that problem and move on.

4)  Check compression, replace spark plugs.

5)  If all these things up to this point are fine, then you probably have a 
FI problem.  These can be tough to diagnose.  When you get to this point 
write back with a better description of your car's symptoms.

Jim
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       Melissa Kepner                                    Jim Adney
       jadney@vwtype3.org              jadney@vwtype3.org
                             Laura Kepner-Adney
                             Madison, Wisconsin
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