I've been chasing what I assume is an air/fuel mixture issue with my 91 3FE FJ80. The car starts and idles perfect at 650rpm and when I first press on the gas, all seems fine. Once the rpms hit around 1500 rpms or second gear the car loses all power and can hardly get up a hill. If I ease up on the pedal and keep pedal below 1500 rpms it goes back to normal but can't get above 10 mph.
My initial thought was some sort of fuel delivery issue. I know I should've tested fuel pressure first but I had just gotten the injectors rebuilt and had all the associated fuel parts waiting to install so I went ahead with installing a new fuel pump and FPR thinking the issue would go away but alas the issue persisted. And before anyone asks— yes, a brand new fuel sock was put in with the new fuel pump and the fuel filter is less than 1k miles old. Peeked into the tank while I had the fuel pump out and its clean. No rust.
With fuel delivery ruled out for now, I then moved into the air/intake system. The throttle body has been off and cleaned of all gunk. TPS and IAC bench tested and all checked out. Now we get to the AFM. At first the AFM passed the bench test also. Resistance check all seemed fine but then I went ahead and plugged the AFM with ignition on to do a voltage sweep check and got back some questionable results.
With ignition on, I back probed E2 and VS while opening the flap gradually and the voltage seemed to move inversely... With flap fully closed voltage is at 3.94v and as I push the flap open the voltage drops. Shouldn't it go up? Could the voltage drop cause the ECU to interpret this as less air? I've included a video of the voltage test as well as a photo of E2 and VC measuring at 5v.
For what its worth, the car's been desmogged also. Could that be contributing to the issue?
My initial thought was some sort of fuel delivery issue. I know I should've tested fuel pressure first but I had just gotten the injectors rebuilt and had all the associated fuel parts waiting to install so I went ahead with installing a new fuel pump and FPR thinking the issue would go away but alas the issue persisted. And before anyone asks— yes, a brand new fuel sock was put in with the new fuel pump and the fuel filter is less than 1k miles old. Peeked into the tank while I had the fuel pump out and its clean. No rust.
With fuel delivery ruled out for now, I then moved into the air/intake system. The throttle body has been off and cleaned of all gunk. TPS and IAC bench tested and all checked out. Now we get to the AFM. At first the AFM passed the bench test also. Resistance check all seemed fine but then I went ahead and plugged the AFM with ignition on to do a voltage sweep check and got back some questionable results.
With ignition on, I back probed E2 and VS while opening the flap gradually and the voltage seemed to move inversely... With flap fully closed voltage is at 3.94v and as I push the flap open the voltage drops. Shouldn't it go up? Could the voltage drop cause the ECU to interpret this as less air? I've included a video of the voltage test as well as a photo of E2 and VC measuring at 5v.
For what its worth, the car's been desmogged also. Could that be contributing to the issue?
