You have a 1982 720 carbeng back fires when Accelerating AND after you get the speed up rus great but if you take the foot off the gas pedal and accelrate again it backfires again everytime please hel?

Answer 1

Backfire in an automobile engine typically results from various malfunctions related to the air to fuel ratio. Usually, backfiring occurs in carbureted engines that are running lean where the air fuel mixture has insufficient fuel. ("Running lean" is typically a sign of mal-adjusted carburetors or fuel injection where there is not enough fuel for the amount of air). Afterfire occurs in engines that have an emission system malfunction (air injection system diverter valve), exhaust leak or unburnt fuel in an exhaust system in which the catalytic converter has been removed. When a driver shifts up and lets off the accelerator, the engine has a moment of running rich or with insufficient oxygen. This causes an incomplete burn which causes the fumes to explode in the exhaust system. The leak itself is the most dangerous aspect. Without it, the mixture would cool enough not to explode. A fuel injected engine may backfire if an intake leak is present (causing the engine to run lean), or a fuel injection component such as an air-flow sensor is defective.

Common causes of backfires are:

Timing - If car is distributor-less

Timing - If a two stroke engine is backfiring every other stroke.

Fuel pressure, fuel filter and pump - leaks and corrosion could cause lack of fuel during the fuel injection event.

Bad wiring in ignition - ..if car won't run for more than a few moments.

In older engines, backfiring may be considered normal. Backfire is rare in modern cars with fuel-injection and computer-controlled fuel mixtures.

Common causes of back fires in the intake manifold are bad spark timing, or incorrect (usually lean) fuel ratio.