I bought a 1990 240 about six months ago for $900. It had a check engine light and it ran a little rough at idle (plus some suspension issues, in the process of being fixed). It's been displaying a 232 code since I got it plus some running issues. I've replaced fuel injectors, mass air flow sensor, O2 sensor (used one of those ones that you splice to the old connector), distributor cap and rotor, plug wires, plugs, fuel pressure regulator, and throttle position sensor. Also replaced the alternator, but I believe that was a separate issue.

All of those were because either they were presenting as bad or a mechanic told me they were bad. Nothing has changed. As a matter of fact things have gotten worse. It used to just run really rich. Now it runs pretty good when you first start it or reset the computer. After about seven miles it starts stalling out at stop lights every so often. Run it further and it stalls out at stop lights and won't stay running above 35 mph unless the gas pedal is pressed. Run it a little more and it becomes very sluggish from a stop and won't pick up speed very well plus the stalling out. And it isn't a sputtering sort of stall. It just quits. The check engine light won't come on for a few days and the last time it did it said it was running rich at idle (code 232) and that the throttle position sensor was acting up at idle (code 133, which is why I replaced it). New throttle position sensor did nothing for it and hasn't thrown a check engine light yet.

Two Volvo guys, three of my gearhead friends, and myself have tried to figure this out but everything we've done does absolutely nothing. Is it just something so simple that we didn't even think to look or is this a game-breaking problem that will cost more money than I can put into it?

 

if it misbehaves when its warm, it might be the fuel injection temperature sensor, which is one of the sensors on the head under the intake manifold.

you probably have Bosch LH2.4 fuel injection, which has some pretty handy diagnostic functions. I would go through the stuff in the 7xx/9xx FAQ as its 99% applicable to an LH2.4 240 ... main difference is, the 240 doesn't have a 'radio supression relay'

Engine Tune and Performance:

and for the OBD diagnostics, see the DTM#2 and #3 tests described
Engine and OBD Diagnostic Codes
DTM #2 can tell you a fair amount about the various sensors, while DTM#3 exercises various actuators on the engine

 

It's not just when it warms up. It warms up after about a mile or two (temps have been in the 80s lately). Well beyond the warm up period is when the problem starts. When it is acting up and you manage to stop it without stalling the idle is low and rough, but it sounds fine when you rev it.

Also, I just talked to one of my family members and they suggested a clogged fuel filter. Which is odd because I was under the impression that a clogged fuel filter causes problems all the time. Not just after running for a while.

As for that sensor you mentioned, I can't find anywhere that says my car is equipped with an injector temp sensor. Also can't find it on any parts supply websites.

 

for a 1990 240 w/ the B230F engine, its volvo pn 1346030, 'Temperature Sensor', and as I said, its screwed into one of several possible positions on the head under the intake manifold. on different b230 engines, I've seen it in different holes. this is NOT the same as the temp sensor that is used for the dashboard temperature gauge, that one is elsewhere (also moves around). there may be other sensors on the intake side of the block too, including a knock sensor and a oil pressure sensor (actually, I think oil pressure is on the exhaust side, but I'm being forgetful).


clogged fuel filters are more likely to cause problems at high throttle and high RPMs than at idle.

 

How would I go about testing said sensor once I find it? I've never run into a car with a fuel temp sensor (not saying much as I'm 22 and have only owned three cars). I'll go through the OBD self-diagnostic tests if the sensor checks out.

 

its not a fuel temp sensor. its a engine temp sensor that is used by the fuel injection to adjust the mixture for best operations with a cold or hot engine.

its a thermistor, it varies its resistance according to the temperature. you could measure it with a digital multimeter in Ohms (resistance) when its cold, then put it in a glass of hot water (or just get your engine hot) then measure it again, and if its in a reasonable range, its good.

from the 7xx FAQ (same engine, differeent car)

* 32F (0C)-- about 6000 ohms within a range of +/- 10%
* 68F(20C) -- about 2300 ohms "
* 104F(40C) -- about 1300 ohms "
* 140F(60C) -- about 600 ohms "
* 176F(80C) -- about 300 ohms "
* 212F -- about 190 ohms "

I'd just take two readings, cold (probably 20C or 30C) and hot (probably 80C or so)... if its even close to right, i'm sure its fine.

there's actually two of these sensors, one for the ignition computer, the other for the fuel injection computer. on some later engines, they are combined to a single sensor with 3(4?) wires.

 

Found the sensor. Now my problem is how to get to it. The only way I can tell is to remove the intake manifold, which means draining the coolant. I'd rather avoid all that.

 

i'd find the other end of the wires to it and measure the resistance. I believe on a 1990, the temp sensor is a dual unit, has two thermistors, one goes to the LH 2.4 fuel injection controller, and the other goes to the ignition controller. the other end of both thermistors goes to ground. I *think* its pin 13 on the fuel ECU and pin 2 on the ignition controller, each of these should be read with an ohm meter to ground with the respective controller disconnected/unplugged

I'm not sure why you'd need to drain the coolant to remove the intake manifold, there's no coolant going through it. when you remove the sensor, the coolant will dribble out, so you stuff the new one in quickly before you lose any significant amount.

 

I too have a 1990 that is having idle/rough running issues. I am begining to think it may be the pickup that is behind the cyl head. I have changed plugs, cap, rotor, plug wires, I substitued known good coil, and known good ignitor. Will check temp sensor as it does run like crap when cold.

 

Well that's good to know. Haynes manual said that the coolant would need drained for intake removal.

 

Here are my thoughts:
1. o2 sensor - I know you replaced it, but you can measure it's output voltage with a volt meter during idle to make sure it's functioning OK.
2. vacuum leaks - look for any split or disconnected vacuum hoses. Spray wd40 where the intake is attached to the head to see if the idle changes, suggesting a gasket leak.
3. Make sure the blade fuse on the firewall next to the coil and fuse 4 (and the contacts) are clean. Make sure the right side of fuse 4 is close to the same voltage as the battery while running. With the car off jumper the left sides of fuses 4 and 6 and listen to make sure the in tank pump is running, and that the main pump doesn't sound stressed (loud buzzing).
4. AMM - again I know you replaced it, but put the old one back in and note any changes in the way it drives.
5. measure the resistance of the LH temp sensor as suggested.
6. ECU - kind of as a last resort, swap out the LH ECU with one from a salvage yard.

 

Tested the temp sensor at the ECU connector. Used a proper ground on the body. It's 2,200 Ohms at 77 degrees (ambient temp). I have to put the throttle body back on to run it to test the resistance at higher temps.

On a side note the inside of the intake was wet when I took off the throttle body two days ago to check it (it hadn't been run for two days at that point). Throttle body itself had a little gunk built up. It wasn't blocking any of the vacuum holes, though.

 

Done checking the coolant sensor. As I said, at about 77F it reads 2300 Ohms. With the temp gauge at between half and three quarters it reads 270 Ohms. I have no way to judge exact temp. Also checked the in-tank fuel pump. It's running and the other pump isn't making any horrible death noises. Still need to test the O2 sensor.

On a side note I've found something interesting. The car still runs if you remove the fuse for the fuel pump (ceramic fuse in drivers side interior panel). Unplugging the fuel pump relay still cuts fuel delivery.

 

I ordered a new temp sensor $17 and a new pickup $35 from fcpgroton. While I am waiting I changed the orings and end caps on the fuel injectors. The car runs much smoother so evidently they were leaking air into the intake. Still not perfect but way better. If it is not the temp sensor or the pickup I now have a spare. Having a spare is many times the easiest way I have found to quickly check a sensor so I don't think I am out anything one way or the other. On long trips I carry all my spares....this scares it and i have therefore never needed them. Leave them at home and there you will be on the side of the road in the hot sun knashing your teeth. I buy spare AMM from Car-Part.com--Used Auto Parts Market pretty cheaply...I got 2 for my 1988 cars for $20 each.

 

there's a rule in motorcycles, whatever you have a spare for never goes wrong

carrying the spare is a form of insurance

 

Got my package from fcpgroton yesterday. I changed the "speed sensor" on the trans bellhousing behind the cylinder head. It is a little bit of a pain to get to. It transformed my car. No more missfiring and starts right up. I like to change one thing at a time so when I finally find the problem I know what caused it. I am not sure why volvo changed from their bulletproof pickup in the distrubutor but starting in 89 they went to this speed sensor. It is a three wire hall pickup one ground. one power, one signal wire. My original pickup has a rubber sheath that was deterioriating and you can see the foil sheilding underneath. It did not look bad to begin with but with just me moving the wire it started falling apart. I guess it is more accurate timing sensing a 60 tooth wheel rather that four blips in distributor. I will buy another (I have two 90 volvos) If you have a 89 up 240 and rough running consider that this may be what is causing the problem.

 

4 blips on the distributor corresponds to two blips on the crankshaft. yes, the new system gives them crank angle (and therefore RPM) with a much higher resolution, so the Jetronic processor knows the engine is turning faster/slower before its had to go around a couple times.