Wife's 1989 244 auto; B230. Has 185K on clock. Good maintenace. For years this car gave right at 29 miles per gallon. Just recently I decided to check it and twice I'm getting 20/21 mpg. Surprised me.

Last year the ECU went out. I was told the original was problmatic, (wouldn't start suddenly; would not switch on FP) I replaced it with the updated part number many of you have done. (Sorry I don't have the p/n's handy) I mention this because this is the only significant change that has happened with this car.

What are the first items that I should check that could be killing my mpg?? I plan to do tune-up items; plugs, etc. I'm asking here because I'm wondering if there is a particular part that degrades and furnishes this economy loss.

I have noticed a drop in mpg's with at least two of our non-Volvo vehicles since Ethanol was given to us. I'd hate to think that is the reason for this because it is a discouraging drop.

Comments appreciated,
Dennis in E WA state

Worse case would be that you have someone going around and siphoning out some but not all of the gas out of your tank.......

--
'86 sedan with 482,000 miles on the original engine and automatic transmission

One last suggestion...dragging brake. If it is a rear, you might never notice in normal driving especially if you tend to be a less aggressive driver.

Most guys here have suggested an IR thermometer to check. If one wheel is warmer than the other after a normal drive, that is probably the culprit.

My 1990 240 DL sedan with the AW71 get 19-21 city with my mildly aggressive driving style and the 10-15% Ethanol gas up here. I also have at least one warped rotor and probably a dragging brake that I have not taken car of yet since spring rolled around.

There are a lot of good suggestions here.

My list of things to check in order would be:

Tune up - plugs, air filter, oil change, distributor/cap (if Bosch)

Intake leaks from decayed rubber parts or loosened lines - especially canister lines
O2 sensor for proper voltage sweep (because it's easy to check)
AMM (running better connected or disconnected?)

FPR - is it getting vacuum and is the line leaking?

Physical fuel leak - are any of the fittings on the fuel pump or filter leaking?


I've seen ethanol and driving style affect mileage 2-4mpg, but 8mpg is a lot. You may also want to do a compression test just for peace of mind and thoroughness.

I hope that helps!
Good Luck

Ethanol will reduce your mileage. Try running a couple of tanks of non-ethanol gasoline if you can get it. It does seem surprising that it would be that much of a drop, though.
--
1966 122s, 1968 142s, 1969 144s, 1979 245dl, 1989 244gl

How long ago was this 29mpg calculated? Was the 21mpg measured the same way, on the same drive, in the same time of year, using the same fuel pumps as the 29mpg? It makes a BIG difference.

I have never gotten above 27mpg in my '93 244 aw71, and that was on a low-speed, all-highway run. My normal around town is 20-21mpg.

Ethanol doped gasoline certainly seems to hurt.

There are probably many things that could contribute to a lower MPG. In my case, the two most common things that have happened on 240s I've dealt with that caused sharp declines in mileage were failing MAF sensors (due to stuck airbox valves) and failing O2 sensors.

A MAF failure would probably also cause other things to go wrong that would inhibit drivability (clunkiness, horrendous exhaust fumes, sudden engine stalls or surges, etc.), but not always - their symptoms have been pretty random in my experience. An O2 sensor failure would cause an overly rich mixture, which would definitely decrease mileage, and you may not notice anything else wrong. On a trip along the west coast a few years back, my friend was badly losing mileage through CA's central valley until we stopped and diagnosed the faulty O2 sensor and changed it out. Presto! MPG was restored.
--
Zach in Vista, CA

1992 Volvo 245 DL, B230F, LH2.4, 175k, M47 (Toaster)
1970 Volvo 145 S, B20B, Dual SU HS6, 145k, M41 (Honey Badger)

I would also check the air filter housing, and make sure that the thermosat has not failed. It usually fails in the open position, allowing super hot air from the exhaust manifold to feed to the engine. This caused my MPG to go down a few years ago.

I take an ice cube out to the driveway to check the operation of my thermostat when it is warm outside. If it moves smoothly, then everything is okay. once the ice cube causes the vent to open you can apply heat with a hair dryer, or just grab the thermostat with your fingers, and this will be enough warmth to cause it to close.

Good luck, and let us know what you find out.

--
If it needs to be maintained, repaired or replaced on a 1990 240, I've probably done it. '90 240DL, 320,210 miles, will she make it to 400K ?? >>You haven't really worked on a car until you draw blood<< :-}

My '85 244 experienced the same MPG drop last year. Turned out to be the Fuel Pressure Regulator.
Dukester

Dukester:
Thanks for the comment. First, our car seems to run fine. Did yours after you experienced the drop in mpg??

Was your fuel pressure reg. leaking?

How did you diagnose the problem down to the FPR?

Lastly, where is the darned thing located?

Dennis

The FPR is located at the front end of the fuel rail.(LH 2.4)
Years ago, I replaced my FPR as a frustrated stupid guess when my 85 244 was running bad.
Of course, the FPR was not the problem, but at least I learned where it was, and now I have a spare.
After months of stress and bewilderment,the problem turned out to be a bad plug wire!...
Now; I say that fresh plug wires are a good investment!