Repair And Fix it

When your car engine hesitates, rattles and shakes when you idle, it might be the result of air entering your engine. This will cause your car to run inefficiently and is typically caused by a vacuum leak. Finding the vacuum leak in the safest manner possible can be tricky, because it can be caused by a broken or cracked vacuum line, a leaking manifold, a leaking carburetor gasket, loose or missing carburetor crews, and open carburetor fittings.

Instructions

1

Start the vehicle and leave the engine idling. Maneuver your hand over the choke housing, cupping it to create an artificial choke.

2

Notice the idle speed after cupping the choke housing. If the idle speed increases, you have a leak.

3

Take a length of vacuum hose and place it by your ear. Place the other end near the running engine, and listen for the leak. Make sure you dont come close to the fan or the fan belts.

4

Mix cleaning solvent with auto transmission fluid, about 50-50, in a garden sprayer or a similar device. Spray this mixture all around the intake gasket. Youll notice an increase in engine speed, if a vacuum leak is present -- along with white smoke coming out of the tailpipe, from the automatic transmission fluid.

The transmission vacuum modulator valve determines how much load is on the engine so the transmission can shift properly. It has a vacuum line that connects to the intake and measures the amount of vacuum in the engine.

High Load vs. Low Load

In order to determine if whether transmission should shift, the modulator valve measures the load of the engines vacuum. Engine load is the measurement of how hard an engine works at any given moment. For example, coasting down hill will create a low engine load, while driving uphill with two passengers and a trunk full of luggage will create a high load. Thus, shift points for the transmission are figured according to the valves measurement.

How It Works Within the Transmission

The modulator valve is a part of the transmission vacuum. Inside the canister of the vacuum modulator, the valve works with a diaphragm and a calibrated spring to measure load. When the diaphragm senses changes in engine vacuum because of load changes, the diaphragm pushes against the valve while the calibrated spring moves against the movement of the diaphragm.

Potential Problems

If the modulator valve is not working properly, the transmission will not shift properly. These problems can arise when the hose connecting the transmission to the engine vacuum cracks or burns, or collapses onto itself.