Does it exist? It's a 1991 940T 4 door, automatic. It's my sisters car and I've done some work to get it running including a new in-tank fuel pump, cleaned the gas tank, new high pressure fuel pump under the car, new fuel filter and rubber fuel lines, seafoamed the top end of the engine since it sat for a year with the previous owner, changed air filter, spark plugs. She gets about 160-180 miles or a bit more recently out of a full tank of gas. According to this Haynes manual the 91 940T had a 60L ~ 15.8Gal tank? So 180/15.8 = 11mpg? What's going on here? I've read the fuel pressure regulator goes on these models should I give that a shot? There is no fuel leaks, no fuel odor around the car.

 

That doesnt seem right. I have the same car with 193k and just did the filter, plugs, and oil and im getting aroudn 18-20mpg in the city

 

Right, so any advice?

 

Check is it throwing any codes. Is the check engine light on? Maybe bad Oxygen sensor, a bad catalyc...

 

possibly the fuel injectors, my buddy had really gunked up injectors and that cost him tons of mpgs.

 

You're going to need to pull codes. Also, O2 sensor has a BIG impact on these cars. Also suspect a bad catalytic converter, easy to check/have checked with a pressure gauge.

Regards, Andrew.

 

The car sat with a bad in-tank and external pump for a year and the gas tank had a little sludgy buildup in it.. maybe that traveled up to the injectors? Is there any easy way to clean the injectors maybe through seafoam or should I just replace them?

Is there a certain code for the O2 sensors? It never pulled any code other than 2-1-4 "Ignition RPM signal erratic" and 1-3-1 is "Ignition system RPM signal" I fixed the 131 code by replacing the crank sensor. The rpms seem to still hop around from idle to 1000 or 1200rpm but it doesn't seem to affect the engine at all. (meaning the engine will NOT rev erratically to 1000 or 1200rpm when the rpm meter jumps like that.. it's only the rpm meter itself doing that.. if that makes any sense)

How would you do a pressure test on the cat?

 

wait. fill the tank and note the exact mileage. drive a bunch. fill the tank again and note the exact amount of gas you added and the mileage difference. THAT is your MPG, not the size of a full tank including reserve. I bet her needle is on empty and she's still got 4 gallons in the tank. you really should do this repeatedly and average as 'full' can sometimes be a half gallon difference at different pumps due to their autoshutoff.

 

I'll definitely tell her to do so but I've seen her fill it all the way up from empty from the moment I got the car running for her and on several fill-ups barely hit 200miles to a tank.

 

I dont think thats the problem... You should do a throttle cleaning. You can try the easy way by removing the big hose in the throttle and start spraying carb cleaner inside the throttle and start accelerating the car. you will notice the car misfiring but keep spraying a bit to clean the system. also buy some fuel injector cleaner a good one..

 

were those fillups 15.8 gallons? if they were something less, recalculate that mileage based on what you actually put in, not on the size of the tank.

again, i've been all the way down off the bottom of reserve, and its only taken like 14 gallons... meaning there was still like 1.8 G in the tank. so, 200 miles / 14 gallons, thats 14.3 MPG. 200 miles / 15.8 gallons would have been 12.6 MPG, a big difference. 14-15 mpg for leadfooting around town with lots of stop-n-go is not that unusual. i have a 850 turbo that can get as low as 10mpg if I really am leadfooting it, although more typically I get 17-18mpg in town, and 24-26mpg on long highway trips.

 

I had a 1995 940 and I made 425 miles on a full tank.. I think theres a problem there. BUt i dont know if in that year the 940 had a different tank a bigger one. But im not sure cause I had a 91 but I dont remember if it was the same tank.

 

oh, i do believe the wagon and sedan have different tank sizes too.

the b230ft definitely gets crappier mileage by a few mpg than the b230f/fd... but as I've said before (twice now?) you can't divide miles by tank size and figure thats what your MPG is. you NEED to divide miles / actual gas consumption

also, its not a bad idea to confirm the mileage, like when you take a long road trip, zero the trip meter when you fill up, drive to where you're going, check the mileage. now go to google maps, and recreate the route and see if the mileage is about the same. or use a GPS. volvo odometers are notoriously unreliable, although USUALLY they work or they don't, and once they stop, they stay stopped until you insert large $.

 

Your right and specially on older models lol.. the only volvo that i had the the speedo worked was 95 940. my 240 that i have now the speedo stop at 67506 miles since whenn yearsssss agoooo lol

 

well, I haven't had a speedo go out yet, but I've seen a couple odometers stop working.

• 86 white 240GL sedan - wife bought new. the odometer stopped at 250000 miles 10 years ago. car is probably over 400K and still runs great, a reliable daily driver currently used by my college kid.
• 89 gold 780 bertone coupe - I bought new, put 25000 miles on it in 6 months and totaled it in a crash.
• 93 beige 960 wagon - wife put lotsa miles on this one, was tail ended by a mercedes on highway 17, and bent but drove home. benz was not drivable.. totalled by insurance. RIP.
• 98 white S90 - wife's ride... bought at 80k. at 170k miles it tossed a timing belt prematurely, we scraped it rather than risking major engine repair
• 96 grey 850 turbo wagon - my daily driver, bought a few years ago with 85K miles, now 120k
• 91 green 940se wagon - just bought as car for college son, 235K miles, dad blew a hose and the head gasket, getting fixed now.

 

A little update for anyone that has a similar problem maybe these are some points you should check.

I ran seafoam through the gas tank and intake as well as the steam clean process >> http://forums.turbobricks.com/showth...+water+torture

I removed the cat test port in hopes I would somehow protect the cat by letting some of the steam and whatever debris the seafoam knocked out loose through that hole but it didn't seem to kick out much.

After the seafoam/water treatment it immediately started to feel more responsive when I hit the gas. Also checked the belts and noticed that the A/C compressor wasn't spinning when engaged and figured since it had been sitting for so long maybe the clutch was done for so I removed the belt that went to the A/C. I took it for a test run and it felt much peppier, very rev and boost happy I filled up the tank, reset the trip odo and told my sis to let it run down to near empty. I guess now we play the waiting game and see if it really did any good.

 

you might have a bad coolant temp sensor ,there"s two of them. the one that connects to the ecu and one that goes to the gauge.the one that goes to the ecu might be the culprit.if its bad it will sent a false reading to the ecu and it will increase your gas milege immensely.the injectors will spew out more fuel because it telling the ecu that the engine is cold and its takes more gas to start a cold engine so the injectors are spewing a lot of fuel more often.i have a 92t 740 ,i was getting 265 miles on a full talk.after i replaced it im getting 315 miles on a full tank 23-25 miles per gallon.

 

where are these two sensors? one on the block, and another on the radiator?

 

The coolant sensors are located on the drivers side of the block under the intake manifold. The gauge sender is located by cylinder 2 and the ecu coolant sensor is below #3 cylinder. When they fail, as mentioned, it makes the ecu think it's about 50 below. As has been already by typhoon Andrew, the O2 is THE most critical sensor in establishing correct gas mileage. Think about it...it is THE only sensor that monitors the RESULTS of the combustion. The ecu relies solely on the input from the O2 sensor to adjust accordingly. Other sensors can be weak or failed...if the O2 is functioning properly, the ecu, especially w/ LH2.4, will learn around the failed sensor and approximate a good fuel mixture...w/o the O2...it's flying blind. The turbos run pig rich compared to n/a cars especially with some age and miles on them.13-15 mpg around town is all most people see. 18-22 open highway is pretty average. To get a read on your mileage you don't need to know the size of your tank or run out an entire tank. Just fill the car up to the filler neck, go drive it 100 miles and fill it up again...save the receipt with the number of gallons pumped. Divide the miles driven by gallons pumped the second time at the station..voila accurate mpg.
FWIW, sedans and wagons got the same tanks 82-92 got the 15.whatever size and beginning in 93 the 19.8 gallon tank. Trying to compare driving range is apples and oranges as the latter carried nearly 25% more fuel.

 

Exactly. I used to think I got bad mileage till I realised I had a wagon without the saddle tank, so only a 60 litre tank.
It is amazing what LH 2.4 will adapt to and not set a code. Also look into exhaust back pressure, it can be measured easily and on a turbo car will kill mileage.

Regards, Andrew.