Quote:
Originally Posted by Tourigjm
How would I adjust the timing in my car if I wanted to ?
|
On a car with a distributor, you adjust timing by loosening a bolt or bolts that hold the distributor to the engine and turn the distributor one way or the other. If you turn it the same way that the rotor turns, you retard the timing. If you turn it the opposite way, you advance the timing. When you are satisfied with the timing, you tighten the bolt(s) so it doesn't change while you drive.
It would be a good idea to know what the recommended timing is for your engine before you adjust it. Often that can be found on a label in the engine compartment. If not, you can find it in a repair manual for your car. Usually the timing is set at idle with any vacuum advance hoses disconnected and plugged. Some cars (such as BMW's) should have the timing set at a higher speed.
To see how you are setting the timing, you need a timing light. You clamp one of its cable ends over the ignition wire that goes to the number 1 cylinder. Most timing lights also connect to the battery. You point the light at the timing marks, which are either on the flywheel (you would look through a hole in the transmission) or on the crankshaft pulley area. The flashing light shows the position of the crankshaft when the number one spark plug fires. You may need to look at a book to understand how to read the timing marks. Sometimes you may need to clean up the timing marks and mark the lines with white paint so you can see them better. Be sure the engine is off before you do that so your fingers don't get caught in the belts.
On some newer engines, there is no distributor and no timing adjustment. In that case you may need to change the computer's ROM chip to change the timing.
Many older cars have something called vacuum advance. It advances the timing when there is vacuum in the intake manifold, except during idle (on most vehicles). It is needed for maximum efficiency because the fuel mixture burns slower when the pressure in the cylinder is lower. If it doesn't work, the engine will still make normal power but its fuel economy will go down. The vacuum advance depends on a diaphragm to move some distributor parts. If it leaks, it may stop working. To test it, you can hold the throttle open a little and pull off the vacuum hose to the distributor. The engine should slow down because of the later timing. There should be vacuum in the hose which you can feel with your finger. With the throttle closed the vacuum may go away. On my Honda, there are two vacuum hoses and two diaphragms. One of them leaked and I had to clog one of the two hoses to get any vacuum advance. The engine worked better at low throttle after that. The diaphragm that leaks is only used when the engine is cold so I don't think it's important to replace it.
Older cars also have weights inside the distributor to change the timing according to engine speed. Sometimes they can get stuck if they get rusty. In my Honda they were stuck and I had to spray some oil into the bottom of the distributor and twist the distributor rotor back and forth to get it to move again. If the weights are stuck in a retarded position, the engine will lose power at higher engine speeds. If they are stuck in an advanced position, starting the engine while hot can be difficult and it may knock during acceleration. When they are free to move, the rotor can be twisted by hand in the same direction as it normally turns and it will snap back (because of a pair of springs) when released.