Causes of Improper Vacuum at Modulator

1. Inspect the engine for the following conditions:
- Inspect the engine for a tune-up.
- Inspect for loose vacuum fittings.
- Inspect for improperly routed hoses.
- Inspect for improperly routed lines.
- Inspect the hoses for a vacuum-operated accessory leak.
- Inspect the vacuum valve, etc., for a vacuum-operated accessory leak.
2. Inspect the vacuum line to modulator for the following conditions:
- Inspect for leaks.
- Inspect for loose fitting.
- Inspect for restricted orifice.
- Inspect for incorrect size orifice.
- Inspect for carbon build-up at the modulator vacuum fitting.
- Inspect for a pinched line.
- Inspect for grease in the pipe (delayed and/or no upshift-cold).