I have a 1997 850 t5 wagon. I have done the pcv kit from fcp, plugs,fuel tank evap lines with new gaskets, oil change, new vacuum lines, and upper and lower radiator hoses all in the last 1000 miles.

Im driving cross country multiple times in this car and my fuel mileage is horrible. I have no cel.
My scan tool reads
0 codes
Mil off
Monitors
5 inc
Catalyst
Evap
02 sensor
02 htr
Egr
3 ready
Misfire
Fuel
Comp

Im not to happy with just parts changing until things are resolved. Everything i have replaced was necessary based on thorough diagnosis and inspection. Im still driving. Im actually typing this in an Ihop parking lot. Any suggestions would be awesome. If i can get my hands on an old snap on brick or similiar scan tool on craigslist i most definitely will so i can do some real time monitoring.

For now Im throwing it out to the community with much love and respect. Thanks to all who spend their time reading this.

 

Have you checked the tires ?? If they are under inflated it will cut into your mileage.

What is your mileage ??

Might want to check / replace the coolant temperature sender as if it's off some it will not throw a code but can cause the computer to go rich. It's tossing a part at a problem but it might be worth it. That or if you can get a thermometer on the cooling system and a reading from the sender through a scan tool to see if they are the same or different.

Does the engine seem to idle and run smoothly ??
Have you inspected the underside of the cap and the condition of the rotor ??
Wires ??

It's a start.

 

I'd also suggest tossing in a bottle of fuel injector cleaner if you haven't yet this year. Either Lucas or Chevron. I'm partial to the Lucas myself
If you have a gummy injector or two it makes the other cylinders work harder lowering performance and mileage.

 

In addition to the good advice from Kfrog, might want to ck the fuel pressure at the rail too.

Ck for two things:

1. The pressure itself; should be around 42-43 psi at idle, and rise a few psi when you blip the throttle. Higher pressure will make it run rich; i.e. poor mileage.
2. After you shut off the engine, watch the gauge; should hold pressure for at least 20 minutes or so. If you see start dropping as soon as you turn off the engine, you got a leaky injector.

Since you're on the road, you probably don't have a fuel pressure gauge with you; pop into an autozone or the like and see if they'll loan you one.

 

Always helps to know where a person is. There's an Ihop down the street from me. I doubt your there, but if you were I'd be willing to help.

 

The most important thing is to maintain humor. I have lost mine a couple times on this journey. Thanks mudpie. Btw im headed to Morenci, AZ tonight and then Boulder for day and Lincoln after that for two months. Anybody that is in the way that wants to help ive got beer or red bull. Thanks guys.

 

We still do not know what your mileage is???

 

Yes and No ... One of the first things I did when I got my 850 after replacing some broken/well worn suspension components was go with a 55 psi regulator on an otherwise stock 2.3T. I read up on it and I've done it on other engines (Not Volvo) for performance reasons.

It doesn't automatically make the engine run richer because the computer using the O2s input will decrease the dwell (on time) of the injector. To a certain point bigger injectors or higher fuel pressure don't really do anything.

They do allow for more fuel on the top end but as long as it isn't too much for the computer to adjust for the computer will simply turn them on for less time at a given throttle angle and RPM. The problem comes if you go too big and the computer can't cut back enough or if it does it thinks there's a problem and trips the MIL and then goes into limp. Then YES, you would have a dog of an engine and it would be guzzling fuel.

If you're starting to do mods and you need more fuel it's cheaper to increase the fuel pressure than to buy five injectors. I can't find the table right now but I think upping the pressure 10psi on our 2.3 engines is like going one size up in injectors.

 

The clock shows 167,000 miles. From the beginning. I replaced the struts and a sway bar link. The rear upper strut mounts. Two tires and an alignment. Then the fcp pcv kit. I cleaned a ton of buildup out of the intake and head. All vacuum lines and upper and lower radiator hoses replaced. I dropped the fuel tank and replaced all evap hoses there and gaskets on top. I also replaced the oil cap seal,dipstick seal, and injector seals. I also had the oil changed, wheel balancing and alignment. All in the last 2500 miles.
Since i left north carolina I have been tinkering to increase mileage. I ran seafoam through the intake to clean valve seats. I ran lucas iinjector cleaner in a tank of gas. I pulled and cleaned the iac valve. I replaced my plugs with the best .028 gapped plugs I could get from auto zone. I think they are autolites. I averaged 17 mpg from Fayetteville NC to Boulder CO. I am now in Thatcher AZ. I averaged 19 on the way here.

The car boggs badly if too much throttle is applied at any point but uphill is the worst and passing gear at any time is unusable. I can balance things out and squeeze 25mpg on the cluster at 55 mph but thats barely touching the pedal. Again too much throttle and it falls on its face and bucks.

I happened across the Hatch Valley chile festival on my way to AZ today. The festival was awesome but the traffic was horrible. I sat in a creeping line of traffic for a half hour. The car idled at 900 the entire time which is what it always idles at. The idle has never hunted and still doesnt. All seemed fine until traffic broke and I spent the next three miles gradually creeping up in speed at 10mpg until it cleared up and let me go 65 to 70 mph for the rest of the trip.
I have not checked fuel pressure but I will tomorrow. I feel like there is a misalignment between the air and fuel. Maybe the ecu is not reading the throttle plate angle correctly or not sending the right values from the maf as the variables change.

I need the testing proceedures with voltages and pins for the throttle body, maf (testing these with a multimeter has never worked out for me, although I do have my osciloscope here), the iac, and i need to look closely at the 02 sensors.

I am being cheap and stubborn when it comes to swapping parts. The fuel mileage has burnt lots of parts money. The stubborness comes from the fact that I want to know whatnis wrong exactly. Not just know its working properly after a massive parts swap. Also im a converted volvo guy from Audi,VW and im learning volvo on this car. I still own a lonely A6 wagon and mk1 that are laughing at me right now. Thanks again guys.

 

Do you have a check engine light ??

(sorry, you posted you didn't have a light)

It does indeed sound like you have a fuel / air issue. Did the plugs you pulled look black from too much gas, carboned up ?? Or were they pretty white ??

 

The plugs that were installed by the PO were ngk r and they had a slotted electrode. The electrode was rounded and worn so I replaced them. The only plugs that Oreilly in some Kansas town had were Autolite double platinums. I pulled the plugs today and they looked ok. The plugs looked pretty good. I put 600 miles of Kansas flat land and 600 miles of Colorado New Mexico Arizona hard uphills on these plugs. I purchased a cap and rotor today and I am installing them today. I tested the maf with my multimeter today. The baseline was right at 1.22 volts and it increased smoothly as I increased throttle. The only thing I have not been able to verify is how high the voltage should go. It went past 5 volts with a quick increase in rpms to high rev I saw 8 plus volts. I have not tested the coolant temp sensor,tps,oxygen sensors,cam position sensor. I have no mil on and that tells me that the cam sensor is most likely good. My oscilloscope arrives here Tuesday on a semi with my tools so Ill be able to do a good test on the 02's Tuesday evening. Any good advice on testing the tps?

 

I don't think anyone has mentioned it, but have you checked the t-stat?

 

I am sure that the t stat is working based on having to follow the full procedure for filling the cooling system when I replaced the upper and lower radiator hoses. I had to wait for the t stat to open before finalizing the fill. All worked well. I did install the new cap and rotor today and although everything I do improves fuel economy a little I am still falling flat on my face at 19mpg with no low end power. Im feeling very impatient about my oscilloscope arriving. Im tempted to just throw in an 02 sensor upstream.

 

If it isn't overheating then yes it's working but that doesn't tell you if it's working properly and bringing the engine up to it's normal operating temp. A weak thermostat that is opening too soon and running 5-10-15 degrees cooler than it should. Colder engine, richer mixture, poor performance, poor mileage.

Just a thought.

 

If the car doesn't like throttle going uphill, that is often a symptom of weak ignition. On most cars, the plug wires are the first thing to go, but of course Volvos are strange.

I find that platinum plugs are hard to fire, which will make weak ignition problems more pronounced, and more stuff gets fried. I generally avoid them, but I guess these old cars came with them. I would be tempted to put on a non-platinum plug, not just in this situation.

 

Man I feel horrible... I'm complaining about 25 - 27 highway with an evap code and a front 02 sensor code. Before I had those 2 codes I was getting 29 mpg @ 79 mph. Matter of fact, I just towed a U-Haul trailer (1600 lbs) 640 miles to Cincy @ 63 mph and got 18 mpg. You seriously have something wrong, and I believe it's PLUGS.

Get you a set of Volvo plugs and put this behind you. Volvo plugs, Bosch cap & rotor, BougiCord wires. That's the only way to go in my opinion. At 55 mph I get 33 mpg with no codes and 29 mpg with codes.

 

 

Oh, I forgot to add, when I towed the trailer to Cincy my car never complained about going up hills. It slowed down a little on 1 hill. If you come through Little Rock or Albuquerque in the next week let me know. I'm in Little Rock till Wednesday, then off to Albuquerque.

 

 

There is also a chance that you have a torn or loose intake tube somewhere. I would start with a good ignition tune up with the proper parts.