I have a 91 wrangler that I put a 89 tpi 305 in. A month or two ago I had a very bad backfire problem so I put in the best spark plugs I could find at stores in my town and I was driving it today and it came back. Is there anything that could cause this to keep happening? I do have a huge intake on it and it is straight piped. Any suggestions? Please help! And thank you!

 

"Backfire" comes out of the intake. "Afterfire" is out the exhaust. Which one do you have, as there are different possible causes for each.

 

It is coming out of the exhaust

 

It is coming out of the exhaust

 

Afterfire (popping out the exhaust) is generally caused by having a rich fuel condition where the gas is igniting in the exhaust. Do you have the engine's air/fuel management system set up like how it was in the car it came out of; oxygen sensors, air intake sensors, etc?

 

I am honstaly not sure. I have the stock obd1 sencer port thing. But I am not sure about the intake, o2 sencers, etc.

 

Need to get under the Jeep and see if you can find any O2 sensors anywhere in the exhaust system. Without those, your engine would be running rich.