anna Posted September 17, 2007 Share Posted September 17, 2007 Hello everyone! I've got a 78 chinook that backfires when I let off the clutch and/or slow down quickly. Does anyone have a tip on where to start looking for the problem? Thanks a lot! Anna Quote Link to comment Share on other sites More sharing options...
picklebill Posted September 17, 2007 Share Posted September 17, 2007 Anna - I don't know how much smog equipment is on your engine, but if it has an exhaust gas recirculating system, I would look there. I would suspect the problem will be in the emissions system somewhere. Could be a vacuum leak also. I hope you solve the problem since it can be a irritating. Bill Quote Link to comment Share on other sites More sharing options...
Gulfstream Greg Posted September 18, 2007 Share Posted September 18, 2007 Hello everyone! I've got a 78 chinook that backfires when I let off the clutch and/or slow down quickly. Does anyone have a tip on where to start looking for the problem? Thanks a lot! Anna Any other symptoms, ruff idle, hesitation, overheating, pinging, have you checked the ignition timing and dwell? When was the last time the plugs and wires were replaced? Backfiring usually has two faces, one it could be ignition timing or possibly a very worn timing chain or two your spark plugs and or wires are not doing their job. Excessive unburnt fuel dumps into the exhaust and can cause backfiring. A simple and somewhat inexpensive diagnostic is to first do a full tuneup, new plugs, wires, rotor and cap and points and capacitor. A proper setting for the distributor is to set the dwell correctly first then the timing. Once set rev the engine and watch the dwell and see if it changes. To much change points at worn distributor bushing and other parts, any change in dwell also changes the ignition timing so its imperative it stays fairly steady. Dwell also controls the energy of the spark produced at the spark plug. When the plugs are pulled out for replacement look at them, compre them to the images in a good tuneup manual as they can tell a good story. Quote Link to comment Share on other sites More sharing options...
nhcamper Posted September 20, 2007 Share Posted September 20, 2007 I have a 77' Chinook and sometimes in the morning it will backfire if I don't let it warm up. Once it warms up a few minutes it's fine. Quote Link to comment Share on other sites More sharing options...
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