Help ... Backfiring!

[wlm]

My 92 Explorer is backfiring a lot. It happens at low rpms (1800-2000), usually around 35-50 mph, and it will backfire several times. It is not unusual for it to backfire rapidly 5 times or more. What could it be -- plugs, wires, vaccuum leak, O2 sensors? Any help is appreciated. Thanks!

 

[yob_yeknom]

Stock exhaust or aftermarket?

 

[wlm]

stock exhaust

 

[mdrut]

Timing...Plugs, wires,etc. will make it miss, but not backfire..Take it into the shop, sounds like it's time for a chain..How many miles on it?

 

[wlm]

137,000 miles on it. The backfire sounds like it is coming from under the hood, not the exhaust, if that makes a difference.

 

[mdrut]

Quote from Haynes Manual..Trouble shooting...Engine Backfires..1 Emissions system not functioning properly 2 Fault in the fuel or electrical system 3 Faulty secondary ignition system 4 Fuel Injection system in need of adjustment or worn Excessively 5 Vacuum leak at the throttle body, intake maniford, or vacuum hose 6 Valves sticking 7 Crossed wires...

 

[yob_yeknom]

Can you hear a knocking sound coming from the front of the engine? The timing chain was bad on my Dakota and was causing a knocking sound and backfiring. Changed it and runs much better now. (my dad owns it now)