I've been having this issue with my '89 240 for a little while now and haven't been able to get a handle on it. First, a little background on it...

I took the ole girl on a road trip for about five hours and she was running well most of the way there but about 3/4 of the way there the check engine light came on and she felt very down on power. MPGs plummeted, began to run super rich, black smoke out the tailpipe, smells like fuel, etc. Normal a rich condition symptoms. Getting code 1-1-3 from the ECU, nothing from the EZK.

Initial thought was to replace the junkyard MAF with a new one, which I did. Letting the battery sit for ~15 minutes unplugged and then starting it back up seemed to fix the issue, but it came back about a day or two later with the same symptoms. Since then I have:
-Checked the throttle position sensor which seems to be okay.
-Swapped out the fuel relay with one of the four I have laying around—no change.
-Unplugged the 5th fuel injector which did not help.
-Fuel pressure regulator does not have or smell like fuel in vacuum line.
-Checked with an MSD coil that we were getting good enough spark.
-Changed spark plugs which again fixed it for a day or so, probably because the other ones were so fouled at this point.
-Checked for vacuum leaks—I found one hose at the top of the engine under the intake manifold which is cracked and could use replacement, however when that hose is plugged there is no change so I'm not convinced this is the issue.
-Unplugged the coolant sensor in which it ran way worse than with it plugged in.

I've read some other posts with similar issues though most never seem to come to a resolution or the ones that did were alleviated by doing something I already have. To avoid throwing more parts at this thing, does anyone have any ideas or routes to go down?

 

Make sure you are not getting UNMETERED air leak past the MAFS. Running rich is usually caused by extra air which causes extra, too much, fuel which fouls things up with the symptoms you describe.

 

i thought unmetered air causes it to run lean, since the meter only sees SOME of the air, it doesn't add enough fuel ?

 

Theoretically, but from hands on experience I've seen it before, one of those mysteries.

 

air leaks in the exhaust can certainly cause it to run rich, because it fools the O2 sensor into thinking its too lean

but the O2 sensor loop has a fairly small dynamic range of adjustment of fuel mixture.

 

I would love for it just to be a vacuum leak somewhere. Maybe I'll just tear apart all the hoses off the engine and see if anything is split in a place I can't easily see. The brake cleaner test didn't cause any fluctuation in RPM but obviously that's not exactly scientific.

Oh yeah, that's another thing I did—O2 sensor replaced to no avail.

 

Something else which is new today: On my drive earlier the temperature gauge went up to 3/4 hot, (which is 'normal' for this car—the needle wanders between 1/4–3/4 sporadically it seems) and then slowly dropped down to 0 as if the car was off. Didn't pick anything up for the rest of the drive and then half of the drive home the next day.

I've read some things where the coolant temp sensor can play some havoc with the running of these engines, though I feel less than optimistic that this is the problem.

 

note the dashboard gauge is a DIFFERENT sensor than the dual one that both the ICU and ECU use.

normally, a 240 has a temp compensation circuit on the gauge, which pretty much pegs the needle dead center unless the car is too cold or too hot. the fact that your needle wanders may mean that either someone before you removed/bypassed this compensator, OR the compensator circuit is flakey. without the compensator, you'd expect the needle to rise to like 3/4 on a warm day climbing a steep grade, or in stop and go traffic, and to drop in cool weather and when coming down long grades with very little throttle. they put the compensator in to prevent neurotic owners from bugging the service people.

if yours was wandering around independent of the actual driving conditions, then its likely this compensator circuit has gone flakey. on some years/models,. it was a separate skinny circuit board stuck into the back of the instrument cluster, but to remove/bypass it, you need a jumper in its place. other years/models, it was fully integrated into the main instrument cluster circuit board making it harder to modify.

 

this is normal .. means nothing ...look elsewhere

 

Interesting. I knew about the compensator and had theorized that this was on its way out previously but I did not know there were two different sensors for the dash and the ICU/ECU. I don't think the previous owner did anything to it as its a single owner car and she was an elderly woman, but you never know.

I'm going to tear into it again today and see what I can drum up.

 

Update: Messing with the car some more today, I unplugged the vacuum line going to the fuel pressure regulator while the car was running. As soon as I did, the idle smoothed out and it seemed to run better. Reattaching the hose or covering the opening of the vacuum hose led it back into the cough idle. The hose is dry and doesn't smell like fuel, but could there be something else going on with the regulator that is making it run so horribly?

 

um, the regulator is setup so the actual fuel pressure is 42 +/-2 PSI *relative to manifold vacuum* ... LH 2.2 cars were 36 PSI +/- 2 psi... so disconnecting that vacuum line effectively raised your fuel pressure by the amount of manifold vacuum, which is something like 7-10 PSI at idle, effectively making the car run a fair bit richer. which suggests its running too lean by default. running too lean is often caused by air leaks downstream from the MAF/AMM mass air flow/air mass meter.

 

Interesting. It's definitely running rich though—horrible MPG, black soot out of the exhaust, plugs keep fouling with black soot and smell like gas.

 

Did some work on the Volvo today:
Compression test showed 170-175-180-170 respectively. The plugs smelled like gas and looked awful when I pulled them out, but that was to be expected.

Pulled off the main intake hose today and saw these splits on the bottom. I wouldn’t think this would be bad enough to cause my symptoms though, right?



In addition to that main intake hose, it seems like the breather hose that the flame trap sits in was also cracked. Maybe a combination of these two?

I also have the ECU coolant temp sensor on the bench and am not getting any resistance readings through it but I'm afraid I am not testing it right/using the multimeter right.

 

absolutely, even a pinhole leak between the MAF and the intake manifold will cause all sorts of idle issues.

the coolant temp sensor has two pins, you measure from either pin to the body of the sensor (ground). both pins should give approximately the same reading, one pin is used by the ignition system, the other by the fuel injection system. if you measure BETWEEN the pins, you're effectively measuring both sensors in series so would get double the resistance.

 

Interesting, I didn't think it would be that much of an issue! I ordered a new one today as well as a PCV and flame trap set up since now only was my vent hose cracked, the flame trap was missing form inside the hose. There is all sorts of grease and sludge coating the engine so while I have everything off I'll just replace it and not worry about it/see if that helps the issue.

I thought that I was testing it incorrectly, thank you for shedding light on that. And thank you for all the information thus far! I've seen numerous threads where people have similar issues but they never seem to be resolved so hopefully we can wrap this one up together.

 

Update: Ordered a new intake hose as well as a slew of other parts to throw at it since I was already in there:

-Intake hose after MAF and before the throttle body
-Knock sensor
-Fuel pressure regulator
-Replaced gaskets on intake manifold and throttle body
-Flame trap "S" hose (Also installed the white filter inside the PCV junction for the hoses as it was missing)
-PCV breather box (There was oil everywhere around that side of the engine, so thought this may be the culprit)

The final result is a mixed-bag. The car does run better...ish. The idle is high now, ~1500 RPMs for an unknown reason and stays that high when warm or cold. It is still running rich it seems, but not to the same degree it was earlier. I took it on a ~25 mile drive and it did not throw the check engine light—yet—but it is driving better. It doesn't appear to be bogging as badly on the highway as it was before, but still doesn't feel 100% back to normal.

Thoughts?

 

did you replace the CTS in the end or no?

 

CTS being coolant temperature sensor? If so, no because my RockAuto package including that and my intake manifold gasket got lost to the COVID fairy.

Eventually, whenever it shows up I will do that also.

 

yes, CTS = coolant temperature sensor.