1. Home
  2. Volvo automobiles
  3. Results of 92 740 O2 sensor tests.....advice?

Results of 92 740 O2 sensor tests.....advice?

I got the new Fluke 114 DVM today and tested the voltage from the O2 sensor. this one has the averaging function and analog bar graph.

Its a new sensor from RockAuto.com. Replacing the old one had no effect on gas mileage, it remained at 16 mpg.

After running a few minutes, at idle, I had 475 mv average, and the bar graph was fluxing all the way from zero to over-range, about once or twice a second.

At highway RPM, the avg. rose to abt 480 mv. and bar graph was fluxing the same way. I think J. Sweet said that at stochiometric, it should be abt 500 mv....so should I conclude that the control system and all sensors are functioning properly, maintaining optimum mixture?

So then either I am a lead--foot (no way), or the tranny is not maintaing proper ( low) RPMs (I am thinking). Like I said, It winds up to 3300 RPM or so going up to hwy speed, and will never shift into third until you manually back off the gas for a second--so its like having only a semi-auto transmission. And it turns about 3200 rpm at

60 mph. I have tried twiddling with the kick-down cable a lot, and can't seem to get the tranny to shift at lower speeds and fully automatically with *any* adjustment. My 88 Camry maintains LOW RPMs....while this Volvo winds up like a top!

I was hanging on to this car beacause its its easy to work on /fix myself.....but there comes a time when the rising price of gas will make it better to buy a recent-model high gas mileage car, and bite the bullet on a monthly car note to pay.

I like those VW diesel engines that get 40 or so MPG!

Thanks, geronimo

Reply to
geronimo
Loading thread data ...

Yeah it sounds like your O2 sensor is working just fine. There's something goofy going on with the transmission though, does it ever shift into 4th? My

740T has a manual transmission, but cruises at around 2300 RPM on the highway and I can usually get around 27 mpg out of it.
Reply to
James Sweet

Ok geronimo...

Go back to basics. Pull out your oil dipstick and look at oil level, condition and smell it. Is it overfull ? Is it discolored ?, Is it thin ? Does it have an acrid/gassy smell ? If, especially the latter, symptoms are present that is an indication that fuel is burning inefficiently and the excess is ending up in the oil. The fact that the H2OS is working nicely suggests that this is not the case but it's a quick way to eliminate one branch of the diagnostic tree.

Like James, I'm inclined to think that your OD is not engaging. Check trans fluid and service if required. The transmission is not particularly complex and mine have always provided good service with limited attention. If you service it you might try LubeGard additive. Every summer I tow a converted VW Type II camper with my 87 240 wagon for 5000 or so miles and have yet to have a problem so the trans itself is fairly reliable in my experience, but I do faithfully maintain things.

With an AT you should get a reliable 24/25mpg and the failure to get it into OD will keep it under 20mpg.

Keep us posted

pat hayes

Reply to
pathayes81946

Nope....the oil looks entirely normal. Only a little darker than honey and no smell. That is what it is, I think... no overdirve, although it is enabled by the button on the shifter. I have never counted more than three gear shifts. The tranny is screwed.

Reply to
geronimo

Most common cause is the wire to the solenoid valve on the side of the tranny.

The relay also commonly fails, though usually the orange arrow on the dash gets stuck on when that happens, but not always.

Check the fuse too, as obvious as that is.

Internally the tranny is probably fine, these are pretty dependable units.

Reply to
James Sweet

Roger on that. I will have to check all that out....our gas bill is getting outrageous.

Check out this google video of this guy who is injecting "free" HHO into his Accord to increase HP and MPG.....

formatting link
&so=0&type=search&plindex=0 I want to build one of these hydrolyzer cells myself and experiment, they're pretty simple to home-brew.

I just wonder if that engine would still be running after 5000 miles of this.....

Reply to
geronimo

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.