Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1990 Audi 100 Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Boost Pressure
- To check boost pressure of turbocharger system, use Pressure Gauge (VW 1397). Gauge is equipped with a valve to lock pressure measurement.CAUTION: This operation requires the use of a chassis dynamometer to safely test components. If dynamometer is not available, testing can be simulated with a road test.
- Attach gauge to vacuum advance at distributor, using "T" fitting supplied with gauge. Ensure vacuum advance unit and charcoal canister purge valve are not leaking. Use hose clamps at all connections to prevent low readings.
- Warm engine until oil temperature is above 176°F (80°C). Accelerate engine to 4000 RPM in second gear with automatic transmission (third gear on manual transmission). Hold vehicle speed constant and close gauge shutoff valve. Record reading.NOTE: Testing should NOT exceed 10 seconds at full boost.
- Boost pressure readings will vary with temperature. Compare results with boost pressure values in the BOOST PRESSURE SPECIFICATIONS table.
- If boost pressure readings are not as specified in table, replace wastegate and retest. If readings are still out of specifications, replace turbocharger.
BOOST PRESSURE SPECIFICATIONS
| Ambient Temperature | psi (kg/cm2 ) |
|---|---|
| -4°F (-20°C) | 6.2-6.9 (.43-.49) |
| 14°F (-10°C) | 6.0-6.8 (.42-.48) |
| 32°F (0°C) | 5.9-6.6 (.41-.47) |
| 50°F (10°C) | 5.7-6.5 (.40-.46) |
| 68°F (20°C) | 5.6-6.3 (.39-.45) |
| 86°F (30°C) | 5.3-6.2 (.37-.44) |
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.