Dwell at 60 all the time

[Ron]

Wow that's great info...I have the two plugs, but only one used (in a manual car). I'll have a closer look as I never noticed the different colors.

At least in a manual car, the correct plugs seem to matter. I have done some continuity testing, and found that the throttle enrichment switch plug is normally open, and grounded when the microswitch closes. However, my unused kickdown switch has continuity, even though it's left dangling in the engine bay?!

Both switches should be normally open. On a manual, the kick down switch is not installed (LightGreen/Green and Black wires).
Assuming you disconnected the kick down switch when checking continuity, it's bad. I'd double check which pair of wires it was plugged into and remove it.

[Ron]

I guess I could try a new O2 sensor and see what happens, just in case that is what is acting up. With my luck the old one will be permanently rusted in place. If that doesn’t do it, I’ll have the Volvo guys down the road from me have a go.

Arggg...I hate intermittent/mystery problems. ...I'd wait until it starts acting up again before taking it to the Volvo guy$, lol. Good luck!!

[CFI]

Arggg...I hate intermittent/mystery problems. ...I'd wait until it starts acting up again before taking it to the Volvo guy$, lol. Good luck!!

Thanks!

[CFI]

Your lambda is working so if the O2 sensor is good you should be OK. Mixture may need a little adjustment to get that dwell a little higher.

What FV dwell range am I looking for on a hot engine?

[Ron]

It should swing between 35°-45° (use 4 cyl scale!), with the breather installed and the access hole plugged.

More HERE

[CFI]

It should swing between 35°-45° (use 4 cyl scale!), with the breather installed and the access hole plugged.

More HERE

Awesome, thank you. Some good news: my most recent fill up indicates 20mpg. Still not what it should be but better than the 16 mpg I was getting.

[CFI]

So I’ve been dealing with a wonky idle and poor gas mileage for a while. I tried a few things but it only got worse: the car would stall when going into reverse, and sometimes going into drive! Sometimes it would even stall if I took my foot off the gas quickly while I was driving! (Idle or mixture too low maybe???)

I THINK I may have finally solved it.

In the last few days I’ve:
Cleaned idle motor
Replaced O2 sensor
Adjusted curb screw, idle switch screw, and the brass screws per instructions on another thread
Adjusted the arm that pushes the throttle plates open
Adjusted mixture using dwell readings (it was waaaaaay off)
Ran the Lambda/Dwell tests per the shop manual

The car now idles smoothly, does not hunt for idle cold or hot, does not stall going into any gear, does not stall when I take my foot off the gas quickly, does my taxes, makes me breakfast, and compliments my hair. Gas mileage remains to be seen but I have a good feeling.

Thanks to everyone for their suggestions and encouragement.

Now I shall put down this iPad, get in my car and DRIVE IT

[David T]

Gas mileage is the ultimate test of how the whole car is running. It is affected by things other than just the motor. Tires, alignment, tire pressure, bad wheel bearings are just a few examples of things that can ruin your gas mileage. Of course if the motor is not set up and running properly, that is the biggest contributor. Always check your gas mileage and know what it is and if you see it change you know something is happening. Make sure your timing is set up right and the vacuum and mechanical advance are working.

[Ron]

Cool beans, AND taders!

[CFI]

I finally got the chance to run a mileage test. I just got back from a 96 mile drive, the vast majority of those miles spent travelling between 55-65 mph. No traffic. I filled up, drove, and didn't stop until I got back to the gas station (ok, maybe one or two red lights, but that's it).

28 MPG!!

I'm so excited! In the year I've owned my car I've never gotten better than 21 or 22 MPG.

Installing a new oxygen sensor and resetting my fuel mixture did the trick.

Thanks to everyone who chimed in with ideas and encouragement.