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Or a lean condition will cause a backfire......

You could try and read the O2 sensor with a volt meter under cruise. And yes check the ignition too. Make sure the mechanical advance s not sticking while you are at it.

Kevin

Yes, but it will be lean at other speeds also. not just when under load in overdrive. Reading the O2 during the misfire will tell you nothing as when there is an ignition misfire, there is a rush of oxygen which will lead you to believe the engine was running lean.


If its lean at other speeds then its still a good test!

Low speeds under a high load are harder to burn, so it may be enough to make a generaly lean mixture lite late (burn slow) and cause a backfire.

A peek at the O2 sensor will show if something is up, looking at the reading just before it goes into misfire should tell you if the sytem is not working right.

Kevin

87 Turbo Intercooled Raider, roller cam, torsen rear diff, LSD front diff, lockup auto with modified converter, V6 brakes, low transfer case gears...