What causes the vehicle to idle down then back up only when stopped or in park?
The drag from the transmission and the power assist for the power brakes andthe extra load of the brake lights on the electrical sytem, may accially slow down the altentor lowering the total system voltage, in the long run changing the voltage at the engine sensers, throwing the computers tune of the motor off some.. cars built since 1980 that have fuel injection shouldn't do this very little or none at all. The reason is that the fuel system has an automatic idel speed motor that catches the idel and holds it at the right level no matter what the load. This system has limits and problems that limit it's ability to keep the idel right. Then theres the other way around. There's a vacume leak or other problem making the engine idel too fast and when the loads are added ( power steering , in gear automatic trans, airconditioner, raditor fan ) bring the engine to the correct level and the system will keep it from going any lower.
Jun 01, 2010 |
Cars & Trucks