Rough Idle and Running Rich

[Nick91WD21]

Hello everyone! I just recently picked up a 1991 Pathfinder SE for hopes to make it into a daily/off-roader. The issue I’ve been stuck on solving is it’s rough idle and that it runs very rich (10 mpg).

The idling symptoms are:

-Struggles to maintain an idle and runs extremely rough. Usually jumps around 350-650 rpm

-It never cold starts and temp gauge never moves above maybe 1/8

-Sometimes idle will be so rough it causes it to die

-Also new plugs and 02 sensor have black fouling after only about 20 miles of driving

What I have replaced:

1. IACV & Connector

2. Air Assist Valve & Connector

3. Both coolant temp sensors & connectors

4. Spark plugs and wires

5. Distributor cap and rotor

6. 02 Sensor

7. Cleaned MAF and TB

8. Jiggled MAF connector and nothing changed (saw the ground wire is a common issue)

ECU codes:

Code 34 - Knock Sensor

(Unplugged the sensor and it still runs the same)

 

I feel like I’m running out of stuff to replace. What should I do? I am going to replace the thermostat next since even after both sensors and connectors were replaced the car doesn’t cold start and the gauge still always reads cold

[Aonghus]

Following. Our problem isn't quite this bad but I'm hoping to learn something