since 1940

Unstable manifold pressure gauge ( bootstrapping ). Fluctuating MP

 2. Dirt in fuel manifold.

 3. Faulty differential or density controller.

 4. Sticky wastegate or bad pressure controller. Lubricate the wastegate butterfly shaft and move the shaft back and forth. If the wastegate shaft squeaks then it is probably sticking when hot. If the manifold pressure increases immediately upon airspeed increase, then the most likely suspect component is the wastegate. For Cessna aircraft the Maintenance manual has a detailed procedure to determine if the engine is bootstrapping (unstable manifold condition). Refer  to the engine section under "Turbocharger Operational Flight Check Procedure".

 5. Lycoming TIO540 -C1A engines-Inspect for compliance with Lycoming Service Instruction 1396, incorporation of new induction air housing.

 6. Incorrect (wrong pressure) spring on wastegate actuator.

 7. Continental TSIO360 -MB. Improper torque on the retaining flange that secures the induction tube to the cylinder head. Reference Continental Service Bulletin M87-4 or latest revision.

 8. Fluctuating oil pressure on turbocharged engine causing fluctuating oil pressure to wastegate. For Lycoming TIO-540 engines refer to latest edition of Lycoming Service Instruction 1279.

 9. Hydraulic lifters malfunctioning. Check for magnetism.

 10. Turbocharged engine - change brand of oil. Controllers are oil actuated and different oil have different viscosity characteristics that might effect controller action.

 11. Turbocharged engines with pressure magnetos - Magneto leaking too much air.

12. Hot air being ingested into the engine. Cessna T206, T210, P210 are sensitive to air leaks from inside the engine cowling which results in hotter air entering the engine. Performance is decreased and bootstrapping occurs at a lower altitude.

13. Intake valve sticking. Causes the MP to dance!

Copyright 2003 by Sacramento Sky Ranch Inc. All rights reserved.  Prices subject to change without notice. Not responsible for typographical or misprint.
Disclaimer: sacskyranch.com contains abundant information relating to aircraft maintenance. The information provided  is not intended to supercede or supplement the F.A.A. approved  maintenance and/or operator’s manuals. Those F.A.A. approved manuals must be utilized when performing maintenance and/or operating aircraft.