2000 Ford Ranger XLT - 2.5 automatic 94k miles

Engine is surging up and down at idle. Undriveable. With each stumble or surge of the idle, the Ignition Switch/Starter Relay clicks. Relay tested (+/- 40ohms and slowly drops) also, relay clicks when replaced with the A/C relay. With the relay removed and ignition on, clicking continues from the top side of the transmission area. Haven’t been able to pinpoint where exactly.

I’ve replaced the IACV twice, new plugs and wires (tested), new MAF, as well as injector 1 and 2. Issues started AFTER replacing injector 1. Replaced again due to faulty suspicion. No change.

Battery is strong. Alternator is strong.

I’m at a loss. Any advice helps. TIA!

 

Update: I have replaced the fuel pump under suspicion that was the issue. However, after about 20 miles the issues started again. This time however, the engine completely shuts off. This is very intermittent as sometimes I can drive it around the block and have zero issues. Often times, restarting the vehicle multiple times clears the issue and I can drive off again. No CEL yet. When I get an idle stumble/surge it flashes the CEL and then goes away.

Could I have a faulty PCM?

 

I was able to drive it to work with a few minor hiccups on the freeway. No stalls.

Went to start the truck again and it would not hold the idle. Fuel pump relay keeps clicking randomly causing rough idle and ultimately, stalling the motor.

I have pulled the wiring diagrams and have confirmed that the relay is getting power (both constant and key on). I do however notice a slight voltage drop with "key on" from 12.4 to 12.1-12.2 that mimics the "surges" I get at idle. Would that cause the relay to trigger and the fuel pump to cycle on/off? I am assuming not...

When I pull the fuel pump relay, I hear another relay located near my transmission that is also clicking or cycling on/off mimicking the surges I get while the motor is running.

Lastly, with Key On/Engine off the CEL flashes on and off at the same time the fuel pump relay clicks. I read that means the PCM is losing power and/or there's an issue with the PCM itself.

Has anyone had a similar experience?