The 1990 740 16 valve Wagon was purchased new and I am very attached to it.
Our family has put 200,000 plus miles on it and I really want to fix it.

So the car got to the point of running very badly.
I took it to the Volvo dealer because the independent shop gave up and could not fix it.

Now after three months and daily support from Volvo technical, the dealer can't fix it.

The car now runs beautifully at speed but it acts like it is going to die at idle.

Volvo has rebuilt everything, checked everything, or replaced anything that could affect performance.

The next suggestion from Volvo is to remove the head and check the valves to see if one is sticking.

My response to the $1300 charge is why is it so rough only at idle. Once you get the car going, the problem goes away and the engine does not miss a beat.

The other suggestion is to replace the injectors with new ones. We replaced them with used ones,
but both sets could be bad. Both sets exhibit the same issue at idle.

Both moves are expensive. I can't imagine why a Volvo technical specialist can't nail the issue.

What would any of you do in this situation?