6-7 months ago I noticed the avg mpg on my 1996 Volvo 850T wagon (2.3 l engine) started to go lower. (It currently has around 150K miles). When I got the car 1.5 years ago it was doing an average 23 mpg; the highest I ever got it was 25.6 mpg. Months ago, it went down gradually to 22, then 20, then 18. Now it is going around 16-17 mpg, and no matter how much I try, it is impossible to get it even up to 19 or 20 mpg. I replaced spark plugs, air filter, tires are inflated properly. The front oxygen sensor is brand new; it was replaced a couple days ago and mpg after replacing it stayed low around 16-17. The electronic display shows everything like before, avg mpg, instantaneous mpg etc. But my odometer gear is broken, and I haven't replaced it yet. I also bought a fuel filter and I am going to replace that this weekend.
Is there anything else to check or replace to make my mpg back to what it was before?

 

When my son in law did his PCV system his MPG went up. Have you checked all your vacuum lines? Is it throwing any codes? Have you cleaned the throttle body?

 

Where on fcpgroton do you buy a new PCV? Can anyone link me to it? Should I buy the one on FCPGroton, or does it matter.. can I just get it at a local pepboys?

 

Dunno about Pepboys but the AutoZone & Parts America near me have excruciatingly little available in stock for my 850 and what the can order is expensive. FCP is the standard around here for parts; fast, friendly and damn good prices...

Non-Turbo
http://www.fcpgroton.com/product-exe...category_id/64

Turbo
http://www.fcpgroton.com/product-exe...category_id/64

 

The PCV is not just one part. It's a system.

I just replaced mine in february - not that tough of a job but be sure to get the intake manifold gasket because you'll be removing the intake manifold and will need to replace the gasket. There are step-by-step instructions on this job out there, just do some searching and you should find it.

Parts will run you around $150 through FCP Groton.

PCV would be your first step.

While you're at it, clean out the throttle body, the flame trap, and check those vacuum lines around there (3 or 4 of them connecting to the vacuum tree) that they aren't leaking. Actually, they're pretty cheap on FCP as well, might as well replace them if you're doing the PCV.

Fuel filter could help.

Do you flush your coolant and transmission? Not sure if it would effect MPG, but i'm guessing it all does.

You can also modify your airbox and remove the thermostat in there - i did it to my '95 Wagon and did notice an increase in MPG. Check www.matthewsvolvosite.com for instructions on that.

 

One thing I don't believe was mentioned was tire pressure. Check to see if they are properly inflated. Also, check to see if you have a brake caliper that is sticking/dragging.

 

btw on all 850 ur suppose to take out the flame trap..thats what all the techs do cause there was a bulletin going around on volvo to take all of them out

 

Hello KALIN850W,

If you can recall the link, could you please post it?

 

what is wrong with this message board, it won't let me post. it says network interrupted, but it is something to do with the text I'm posting... some kind of filter or something. I can't post what I want.

 

So for whatever reason, spam filters or something, the text I enter in this thread, when I click ok it says connection interrupted. So my solution is just to take a screenshot of gedit, and you guys can read my message that way. fyi. if anyone was wondering why I did this.

 

also, how do you actually test a vacuum leak? If a hose looks fine, How can I test if there is a crack or whatever.

And what is the deal with this hose:http://www.fcpgroton.com/product-exe...category_id/12

$98 for one hose? wtf?

o yea, some more info on the car. I have a rough idle, it sort of hiccups a little when idling. And it feels like there is a lose of power. There is some gas smell from the exhaust, and there is no water bubbles in the exhaust like there used to be. It seems dry.