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Dies sometimes when slowing to stop[ALL/1988] posted by Don Willson on
Saturday, 31 January 1998, at 12:25 a.m.
I have a '89 760 turbo with the EZ-117K ignition system. On several occasions the engine has died for no particular reason. As I now remember back I believe most cases occured while driving in town at moderate speed when I came off the throttle while coming to a stoplight. In each case it would not restart immediately but did within a minute or so.
When I read in the Volvo Ignition System Fault Tracing manual I find that there are two throttle closed signals:
Idling when stopped and no particular power is needed. In this case the spark is retarded to give a smooth idle by reducing peak combustion chamber pressure.
Engine braking which has the higher RPM and is a compromise between lowest emissions and minimum fuel comsumption. A second paragraph says "Most of the electronic fuel injection systems used feature a fuel cut-off function which intervenes under engine braking conditions. In this case, the fuel system control unit is also supplied with a full-closed throttle signal and keeps the injectors FULLLY CLOSED (emphasis mine) under these conditions."
As I see it I have a problem of going from engine braking to idle configuration. Any suggestions? Possibly a slightly faster idle or a tighter adjustment of the throttle switch?
Re: Dies sometimes when slowing to stop[ALL/1988] posted by R. Abel on
Saturday, 31 January 1998, at 6:42 a.m.
You're probably on the right track, but make sure nothing more basic is causing
the problem before you tear into the more complex. Clean the throttle body,
change the air filter, check the PVC ventilation, etc. first.
I would also want electrical problems ruled
out (my '87 740 died intermittently at low idle - it turned out to be poor
ground connections at a junction near the passenger kickboard - turned off the
fuel pump, processor, dashlights, you name it. A Volvo tech. bulletin does
state though that they changed the connector after '87 so they must know this
was a problem, and have hopefully fixed it). Good luck.