Volvo: back fire, 1996 volvo 960, volvo 960

Question
Why did it blow off the hoses that connect the motor to the intake manifold? the 1996 960 volvo has 6 hoses connected to the intake manifold from the motor
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The text above is a follow-up to ...

-----Question-----
My 1996 volvo 960 keeps backfiring. When it back fires it blows the air control system and it then won't stay running. What causes it to keep blowing a hole in the air control duct?
-----Answer-----
Ron,
A back fire usually means that you have a lean fuel mixture or timing that is off. Check the cap, rotor and wires as they get old and cause misfiring cylinders. A 96 should set fault codes. Have those codes read and follow them out.

Answer
Ron,
If there is a back fire in the cylinder and the intake valve is open the explosion then blow off the hose. Keep in mind that those hoses are getting old and soft making it easier to tear apart when the back fire happens. This makes me think that the timing is off. To be safe pull the front cover and check to see that all the marks line up on #1.TDC.