2011 Ford Fiesta SE engine shuddering/diving at start/ignition.

[prettypotato]

Hello all,

New here my wife has a 2011 Ford Fiesta SE which is our current daily driver at 165k mi. I'm working on rebuilding the engine on my truck. We are trying to keep this little car alive as long as possible while we save. I opened the bonnet today and looked over the engine and found that things are a lot more accessible than I expected when it comes to maintenance. Currently the car is experiencing a few issues, but the primary issue I'm currently interested in hearing some in put is what the title says.

On start up on a cold soak the engine will turn over, but after the first ignition/combustion stroke it will dive down to near dead/stop and then rev back up to idle quickly.

• I've noticed it is much more prevalent/apparent when the vehicle has been in the sun/heat.
• I have noticed that the radiator/engine fan has been turning on when at idle at stop lights and stop signs.
• No check engine lights have been tripped.
• We do have rats/mice that like to get in here.
  • We had to ditch the engine bay hood insulator
  • I had to take the windshield wiper tunnel cover off and install mesh to stop them from going in there.
• The AC compressor has been busted for roughly 1.5 years (I'm hoping just the clutch)
  • The compressor will "growl" (sounds almost robotic/electronic) when the AC system has been engaged (including defrost).
  • "Growl" is not apparent when AC system is off.
  • Cold air is rare, but does surprise us at times when we accidentally run the AC system.

Future maintenance plan
Replace:

1. spark plugs, ignition coils, ignition wires
2. Compressor, expansion valve, AC receiver drier (hope there isn't "black death")
3. Replace cam position sensor?
4. Clean throttle body & MAF
5. Coolant refresh
6. Transmission Oil Change.
7. Silencing the TPMS's

Does anyone have any suggestions or had similar symptoms with their Fiesta?

Thanks,

- Potato