DaveT

I have used NGK for decades. They last a LONG time, never had any problems with them.

I 'm not an expert on EA81s. But the flywheel is likely different. But you have one. On an EA82, the flywheel for a standard shift is a flywheel. On an automatic, it's only a stamped steel thing that attaches to the torque converter. There might be a few other little differences in the vacuum lines, but I'd think that could also be swapped.

Sounds like it's time to investigate 3D printing.

There should be a wire from battery - to the body.

What Tom wrote.

Sounds more like drive shaft to me. It spins way faster than the wheels.

Most of what you describe sounds normal. I've been driving these models since about 1988. I have noticed that when the voltage drops more, it has been when I've had an older battery. If you are totally stuck in stop & go traffic, with a lot of stuff on, it will drop even a new battery. But if you drive a good distance / time at speed, then pull up to a stop, and it drops rapidly, it might be time for a new battery. This is assuming the alternator is working normally. I always put in the biggest battery I can squeeze into the space, not the dinky one that the cross reference books recommend. Random idle RPM issues and the other running less than well things you describe could be caused by a partially failing CTS [ coolant temperature sensor] It is a 2 wire thermistor that the ECU computer uses to control the engine. It is not the one wire sensor that the meter on the dash uses. It should have an O2 sensor in the Y pipe, before the first Cat. It is used to control the fuel air mixture once the engine is up to temperature. It can fail in a way that burns out the cat, but does not throw a code. I have not had an experience where the O2 sensor effected drive-ability. My 86 carbed 4WD 3 speed auto wagon had a relay in the AC system that would automatically disenguage the AC compressor when you stomp the gas. The 6 newer SPFI ones I've had / have, none had that.

The bolts were over tightened. And or rusty. The brass inserts in the plastic strip out and spin. Anti siese or grease can prevent this. I decided to run one of my cars without covers a long while back, after seeing several other members go coverless without trouble. I have had no trouble either. I keep the back pieces in place.

If you pull a vacuum line, plug the end, otherwise air gets sucked in and throws off the mixture .

It would be extremely unlikely that all 4 spark plug wires failed completely at the same time. How are you testing for spark? If there is no spark from the coil, timing, cap,and rotor have nothing to do with the lack of spark...

The end of the hose looks like it broke off either the EGR solenoid, or the purge solenoid.

I'll add this - if the 2 radiator hoses are due for replacement, replace the other 5 smaller cooling system hoses. They are likely in worse shape.

Measuring high voltage can be done. You need specially built high voltage resistors. Or expensive HV probes. Several hundred megohms total. High voltage resistors are very long so the voltage doesn't just arc around them.

Using 4wd with the lack of power wouldn't hurt anything I can think of.

What kind of transmission? Auto / manual / speeds? Try to find a factory service manual, on ebay for example. There is no substitute for a FSM. There is some information on here. With more details, it's likely someone can give you help with trouble shooting. I've had several of these cars, the alternators pretty much need rebuild at 150,000 miles.

Try this: Drain it, let it set with the plug and dipstick out for a good few days. For drying out. Put in new oil, or if the old oil will separate form the water and gunk, put it in. Take it for a test drive.

Dashboard lights are not controlled by the ECU, except for the check engine light

That is it, exactly.

There is a mod kit to fix the smoke on long high g turns.

The thing I think you have to watch out for is the position of the sheaves for the V-belt. One version is slightly different offset than the other, so if you have the wrong one, the sheaves are not aligned with the others, which causes problems.

I've used the lighting relay that NAPA stocks. Something like 30 amps.

Gaskets for both styles of case All the seals, O-rings, Servo pipes, thrust bearings [the long shafts at the top are not part of the kit] When I ordered this, there were still about 8 left in stock. About the same number of oil pump drive shafts were left also. Servo pipes and some of the gaskets were no longer available separately.

The rear ones are a lot smaller diameter and thinner

.001 volts is very small. It could be a meter error, unless you are using a high quality meter that costs well into 3 digits... I have not investigated the exact technology that makes O2 sensors work, but any 2 dissimilar metals make a thermocouple, which will produce a very low voltage when there is a temperature difference between them. Or it could be stray noise or the like. I believe the test sugested above would involve keeping the sensor connected to the ECU, and tapping in with a meter. Then driving around while someone else notes readings. You also have to run the engine up to operating temperature before the ECU uses the data from the O2 sensor to adjust the mixture.

I had one rebuilt at a local drive shaft shop. Inspect the spare one, if it looks ok, run it while searching for parts or a shop.