I have an 87 240 DL that has had a good amount of problems in it's time with me. Some of them have been solved by a new fuel pressure and a new O2 sensor, but it seems to be going to the wayside again. Lately it's been stalling (in extreme cold just after startup) running kinda rough, getting terrible gas mileage (worse than the usual 15/16 mpg it gets) and it's putting off a weird smell. I'm thinking it's running rich. Also it may be helpful to know that my preheater hose vanished and I haven't addressed that problem yet. I keep reading about checking for vacuum leaks, but where/how should I check them?

Any help would be greatly appreciated, I hate blowing money on gas.

Thanks, Jeremy

Others have mentioned the ECU's coolant temp sensor. Another symptom of this is intermittent stumbling under acceleration. As the engine RPM's rise under moderate accleration, you will feel a series of flat spots as the engine hesitates. This and a drop in fuel economy were cured on our 83 by replacing that sensor.

Also ensure the basic engine tune-up stuff is OK. Clean air filter, good spark plugs, wires in good shape, ignition timing correct, thermostat good (I use the 92C one in all our Volvos), airbox preheater hooked up and its thermostat OK...the usual.

If the car has been running that rich for that long, I'd also check the catalytic converter for plugging or melted matrix.

I have seen 33MPG from our 83 (M46/OD) back when it only had a few thousand on the clock, and 55 national speed limit. Twenty-one yrs later it will get about 28-30 on the highway and low 20's in town. So should yours.
--
Bob (81-244GL B21F, 83-244DL B23F, 94-944 B230FD; plus grocery-getter Dodge minivan, MGB, and numerous old motorcycles)

I'd would say it was the coolant temp sensor too, except for the fact that it was replaced. It does hesitate on the first acceleration of a drive a lot, but not after that. I think vacuum leak, so I'll check the hose tomorrow.

re: "...worse than the usual 15/16 mpg it gets...."

Just as a point of comparison, that mileage is worse than just awful. I have a 1984 240 that I regularly get 20 mpg in 'lead footed' mixed suburban driving (no highways), and my wife has a '93 240 that gets 25 in the same (although not lead-footed like my) driving, and almost 30 on steady highway driving.
Even my '75 164 does better -- 17 to 18 mpg (sometimes 20, miraculously). So be sure that something is terribly wrong.

re: "...and it's putting off a weird smell...."

Unfortunately, you didn't describe it other than saying that it's "weird" -- what's weird? Doesn't help much. Is it a gasoline smell? The 'winter' oxygenated fuels can be 'weird' to some people -- kind of 'fruity'. Is it the 'rotten eggs' smell of a defective catalytic converter? Try to give us some comparison.

Best regards,

Sorry about the vagueness. It's a gasoline smell I suppose. Not raw gas, but a gassy smell. Not rotten eggs, not fruity. In my opinion, it's something involving the gas/air mix. The mileage started around 16 when it was stalling back in the summer, then when I replaced the FPR the mileage seemed to get worse, with the new O2 sensor, no drastic change, maybe even a little worse, and now that the preheater hose is gone, it's awful. I'm talking like 80 - 90 miles to a half tank, it's nice if I get 200 miles out of a tank of gas. If there's any other symptoms you want me to look for just ask me.

My email is MarchingAnt86@juno.com and I check it often.

Oh yeah, a lot of times just after startup, when I give it it's first real acceleration, it hesitates for a few seconds, then "gets going" and accelerates.
If there's anything I can do to help power/gas mileage I'd love it.

Thanks again, Jeremy

Sounds to me like its the engine temp sensor.

I agree about the temperature sensor, the one for the fuel injection, not the one for the gauge. While I was changing the sensor I would also make sure that it had the proper thermostat installed. Later, rcs.

Is this the coolant temp sensor you're talking about, b/c I had that replaced along with the O2 sensor about 3 months ago to solve a starting problem. The mileage was still terrible after both of these replacements.

You are talking about the engine coolant senor. There is one for the temp guage and the engine computer sensor is closer to the fire wall. If the one you intalled is working (maybe a defective one from factory or incorrect one), the other other things I would check are the fuel presure regulator. You may also want to check the AMM.
And as a last resort the wiring harness and the computer.

Oh, by the way, I have one more symptom for you.

It revs up when I put in park and stays higher than idle, but will kick back down if I put it into drive.