What's causing my 351 Modified to start backfiring...?

Asked by Jun 24, 2015 at 09:34 AM about the 1979 Ford F-150

Question type: Maintenance & Repair

Recently, my '79 F-150 has begun to backfire and it's getting worse.  It had been running rough so I replaced the plugs, wires, cap and button(?)...  But now, the backfiring...! I know I have the wires in the right order as I replaced them one by one...  Could it be vacuum, timing or other (electrical)...?

7 Answers


Check ignition control module.

Obviously I'm not a seasoned mechanic - but I am mechanically inclined... Is that under the dist. cap also...?


That is correct


Whoa there Firebird, it is a Ford not a Chevy, the ignition module is on the fender, close to where the jack is mounted. I would recommend replacing the module and the distributor pickup coil especially if they have never been replaced. Take care when removing and reinstalling the pulse wheel, you don't want to break it or loose the retainer pin.


Thank you for the correction tennisshoes


Your welcome firebird.


Is it backfiring through the intake manifold or an afterfire through the exhaust. Since you replaced plugs and wires and distributor parts are you sure you replaced them correctly to the proper cylinder? Is there a chance you moved the distributor slightly, could affect the timing. Hopefully you do not have a bent valve.

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