I have a 1990 240 wagon, looks and drives good, except that it won't run.

I've put significant money and work into it (even a differential - how weird is that), but a recurring problem has now rendered the car useless.

It runs so rich that it fouls the plugs (solid, deep black) in one minute on a cold-start attempt and within 10 minutes if it's a hot enough day.

We've (read: my mechanic has) swapped out every electronic component - boards, regulators, sensors, etc. - from a car just like mine that runs great.

My mechanic and others he's talked with say that it looks almost certainly like the problem's somewhere in the wiring harness.

There is no way I can spare the time to weave a new harness in, though it sounds within my skills.

A new harness is boocoo bucks, esp. with labor, even though my mechanic will give me a big break because I've given/referred him so much business.

So, here are the parameters:

* I'm going to have to sell the car soon anyway (say a 6 mos./a year)

* $200-$300: Could run another diagnostic - a guy can do some magic and get all kinds of readings from the computer, and *possibly* notice a weird/missing readout, finding the specific problem wire. Ten pay to fix the wire.

* $1000, give or take,: run a new harness and *maybe* this will fix the problem

* Junk it (and break my heart)

* Car's probably worth $2,000/$2,500 around here

My first inclination is to run the $200-$300 diagnostic, hope to find the wire(s) and pay a little more to fix them. If no problem is found, weep and access the situation again.

Second inclination is to go ahead and replace the harness, betting that will fix the problem.

Third, distant third, is to junk it.

At best I have a car worth a few hundred to a thousand dollars more than it cost to fix it. I am afraid that addressing the wiring harness at some $1,500 expense might not fix the problem, leaving me with a near-worthless vehicle.

What do y'all suggest?

(BTW: If anyone in south central Texas needs a great mechanic, let me know. Mine is only charged me an hour of labor to get my car to a friend 20 miles away, swap out all the components, and get it back.)