Here's my issue I have a 2003 Land Rover with a 4.6 Sai I swapped it out for 2001 4.0 non Sai and now I'm having backfiring issues... I've looked everywhere for help and I can't seem to find any except for this one person overseas.. he helped me with the swap and now I can't get over this backfire issue if anybody can get me through this I have a 4.6 engine block and I have 2001 disco body with extra parts and interior thanks in advance I'm in Harrisburg Pennsylvania United States

 

Do you know anything about the history of the engine you installed?
Also, are there any trouble codes stored in the computer?

 

First off did you change the air box and mass airflow sensor when you did the swap or leave the 4.6l maf and tube. The reason I ask is because the diameter of the tubes are different as well as the maf's. This could be causing a crazy lean condition trying to overcompensate for the air coming in and causing your backfire. Second, did you swap ecu's also.

 

I did this exact swap.

Mine was a 4.0 GEMS to Bosch conversion.

If you didn't change out the ignition and fuel components and only changed the block and heads, I'd tend to lean toward something in your heads

 

4.0/4.6L intake tube won't cause any issues and the actual MAF Sensor itself is identical between the 4.0/4.6L engines. The slightly bigger housing is the only difference.

Have you double checked your firing order? Made sure the IAC hoses are good and tight?

 

sorry for the late reply.. the engine was in my 2001 and it was good only the transmission went out because of a loose drive shaft

 

sorry for the late reply.. yes I double checked the firing order and made sure all the hoses are good and tight I even hooked up an obd2 scanner and it didn't show anything about a backfire but while in my garage and idling it'll backfire every 4 - 7 Seconds