I have a 75 Hilux with a 20r and stock rebuilt Aisan carburetor. The problem I am having is that when I drive on the freeway the idle rises up and when I turn it off im getting a loud backfire that sounds like a gunshot. I have an electric aftermarket fuel pump that the P.O. had installed. I installed a fuel regulator and it is set to 4.5 psi. I have the distributor all the way advanced because the dist. Advance does not work and I have noticeably less power when attempting to get on the freeway when im at the right ignition timing. I have new NGK spark plugs and wires. I have searched and could not find what the fuel pressure should be and can not find a return for the fuel. Any help would be appreciated, thanks!!
Well, I did some research on my own and signs pointed to a lean air mixture causing cylinder temperature to go up and backfiring when shut down. I fixed my fuel pressure but it only worked 2 out of 3 times. I have my EGR valve capped off.I have had it capped off since January and this problem just arose. The temperatures were a lot cooler, around 510's but now we are in the 80-100. Would the EGR valve not recirculating cause a backfire after driving on the freeway when I turn it off? Its the only idea I have at this moment since the EGR valve is only active during freeway cruising.
