1987 244 n.a. - fully serviced, but still lower mpg and possibly rich - adjust mass airflow?

[everyhumanvovo]

So, have replaced all standard tune-up items - oil, air filter, plugs, checked vacuum, clean pvc hoses and screen, oxygen sensor, etc. Engine still relatively strong, now near 20 mpg, but used to get closer to mid 20's. Also, replaced rusted exhaust pipe and down pipe and did not replace shot cat coverter. I think it may be running rich and wondering if I should attempt adjusting mass airflow system at all. Have never had any visible exhaust, except in colder temps. Any insights much appreciated!!!

 

[Harlard]

Have you done any of the recommended diagnostics other than throwing parts at the problem?

 

[Souped]

What do your plugs tell you?

Edit: I don’t remember getting any better than 20 in my old Volvos.

 

[Jack]

go hunter s Thompson and add 60 psi to your tire pressure

 

[Khrrck]

what's your driving pattern (mostly stop and go, mostly highway, mixed)?

automatic or manual?

I got very low 20s in my '87 245 auto with mixed traffic driving usually. sometimes approached 30 with long highway cruises.

would not recommend changing mixture without feedback of some kind (wideband O2, someone with a tailpipe sniffer, etc)

 

[johfraser]

Smog check on dyno
Install a wide band O2 sensor with monitor
Plug color
clogged cat
brake dragging
tires
trans slipping
odometer
your driving style and habits

 

[everyhumanvovo]

Thank you much all. Diagnostics ? Tail pipe check. Will check plugs. Brakes have new pads and rotors which are from past year or two. Do not think there is indication of brake drag. Is that your set up Harland?! dual cam!! Only part I threw at it was O2 sensor with couple 100 thou on it likely. The exhaust replaced was in need from the salty rust and other stuff is routine.

Should I put a cat back on for the spent one removed? Was told at time in moment of repair it was not required because of year age, but I do want to preserve the world. Would this provide back pressure and actually be better in any way otherwise with performance? Engine mostly all clean and well maintained but am away from Volvo mechanics, so have to figure this without local expertise. I am just thinking it may be running rich, because of exhaust odor and lesser mpg than I like. I expect exhaust would be cleaner with a cat which am willing to have installed again. It still pulls nice at 3000 with lumpy cam from Portland fabricator now defunct, and IPD adjustable cam,, a decade back.

I punch it all the time, well sometimes, and sometimes very lightly on pedal, and like to have the rear wag and slide some on hard accelerating turns. I mostly drive it on few short mile round trips and then a few 15 mile highway round trips each week. Fairly evenly between small city and highway driving. Not much longer highway drives of late. Any favorites on spark plugs? Think I went back to Bosch copper originals last year. Oh and did install new nice plug wires last year that was necessary..

Tires already at 35 psi, but maybe 60 is the answer.

 

[Souped]

Best adjustment for fuel economy is the nut behind the wheel.

Yes! Get a cat. It will be less stinky. It’s a filter.

 

[Khrrck]

I punch it all the time, well sometimes, and sometimes very lightly on pedal, and like to have the rear wag and slide some on hard accelerating turns. I mostly drive it on few short mile round trips and then a few 15 mile highway round trips each week. Fairly evenly between small city and highway driving. Not much longer highway drives of late.

Sounds like a recipe for low mileage to me.

 

[johfraser]

Glossing over the possibilities will diffidently not increase millage. Pick one thing at a time and use valid tests to eliminate them. Are you sure the millage data is correct.

 

[dl242gt]

You won't get stock Volvo mileage with a aftermarket cam and enthusiastic driving. That said I use an aftermarket cam in my wagon and it stays around 20mpg around town even though I rev it up all the time. So it seems like your mileage is about right for a upgraded engine.