Jump Timing?

[AlfaNeely@xxxxxxx]

In a message dated 4/15/2003 12:05:10 PM Central Daylight Time, 
owner-alfa-digest@domain.elided writes:

> 
> Date: Tue, 15 Apr 2003 08:23:01 -0400 (EDT)
> From: tenkiller@domain.elided (tenkiller)
> Subject: Jump Timing?
> 
> The other day,  my '91 Alfa Spider and I were going down the road at
> about 100 mph and upon accelerating,  suddenly there was little power
> and we started decelerating even with the pedal all the way to the
> floor.  When we had purposly decelerated ,  the motor ran very roughly.
> It was obviously missing but still drivable.  The spark plugs are brand
> new,  as are the plug wires.  The rotor button is also.  I had just that
> day had it serviced.  
> 
> I had to take it to a guy who had worked on it before because he is near
> me and where I usually take it is 2 hours away.  He "fiddled" with it a
> while and has determined that it has "jumped timing" and with doing so,
> it has warped 2 valves and needs about $700 work.
> 
> What happens when a car "Jumps Time"?
> 
> Alan C,
> '91 red Spider Veloce
> 

       I always suspect whatever was just serviced and wires and hoses near 
what was worked on that might have been knocked loose during the service.  
Pull the distributor cap and see if it is OK.  If the cap was not attached 
correctly, it might have slipped off center and knocked the end of the new 
rotor off.
       Jumped timing is rare on a chain driven camshaft.  I had it happen 
only once on the first Alfa engine I ever built.  I had failed to get the 
wedge that holds the chain tensioner installed correctly.  Upon hard 
deceleration, the chain jumped time.  Under acceleration, the timing chain is 
less likely to jump time as it is under tension.
       It is simple to check the cam timing by removing the valve cover.  Did 
the mechanic remove the valve cover?  However, the timing mark on the 
Motronic crank pulley is on the back side and a bit hard to find.  Once you 
find the mark, clean and paint it for future reference.
       If the engine is out of time, it has probably bent the intake valves.  
It will have little or no compression in that / those cylinders.
       There are many things to check before removing the head for a $700 
valve job.

Ciao,
Russ Neely
Oklahoma City
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