Vacuum Throttle Valve Diaphragm (Modulator) Test
- Check System Integrity
Inspect all vacuum hoses and connections for leaks or damage. Disconnect vacuum hose at diaphragm connection and inspect for leaking ATF. Repair as needed. Go to next step. - Check Vacuum At Modulator
Ensure ignition is off. Disconnect vacuum hose at modulator valve and connect vacuum gauge to hose. Start and run engine at idle. Vacuum should be 15-22 In. Hg. If vacuum is not within specification, inspect and repair vacuum hose. If vacuum is within specification, go to next step. - Check Modulator Valve Function
Turn ignition off. Remove modulator valve from transaxle. Connect hand-held vacuum pump to valve. Apply 16-20 In. Hg of vacuum. Ensure vacuum is held by valve. Release vacuum and verify that valve moves freely. If valve is functioning correctly, go to next step. Replace valve if it fails testing. - Check Vacuum Diaphragm Rod
With modulator removed, measure depth of vacuum throttle valve (dimension "N"). See Fig 1 . Measure length of throttle control valve rod. Ensure correct length rod is installed. Refer to the THROTTLE VALVE ROD DIMENSION CHART . If correct rod is installed in transaxle, inspect operation of vacuum throttle valve in valve body. Install correct rod length as needed.
THROTTLE VALVE ROD DIMENSION CHART
| "N" Dimension: In. (mm) | Rod Length: In. (mm) |
|---|---|
| 1.0 (25.4) | 1.16 (29.5) |
| 1.0-1.02 (25.4-25.9) | 1.18 (30.0) |
| 1.02-1.04 (25.9-26.4) | 1.20 (30.5) |
| 1.04-1.06 (25.9-26.4) | 1.22 (31.0) |
| 1.06-1.08 (26.9-27.4) | 1.24 (31.5) |