What to do about an '81 backfiring Chevy...short of buying a '91.

Dear Car Talk

Dear Car Talk | Feb 01, 1998

Dear Tom and Ray:

I have an '81 Chevy Caprice and it backfires. What do I have to do to correct
this problem? -- Lawrence

RAY: Get a '91 Chevy Caprice.

TOM: Most of the backfiring I've seen on these cars is the type that occurs
under the hood, rather than out the tailpipe. So I'm going to assume that's
what you've got.

RAY: And it's usually caused by one of two things -- either bad ignition timing
(which is often the result of a worn-out timing chain) or, more likely, a weak
accelerator pump in the carburetor.

TOM: When the accelerator pump is really weak, the fuel mixture becomes so lean
that the flame in the cylinder propogates too quickly ... so quickly that some
of it sneaks out the open intake valve. And that popping sound you're hearing
is that part of the combustion that's taking place in the intake manifold.

RAY: So check the timing, Lawrence, and if it's OK, then a new accelerator pump
or a carburetor rebuild might be in order.

* * *

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