My newly rescued, poorly maintained 1988 240 5 speed has a problem I can not diagnose.
Starts easily.Idles a little rough. Runs well with the exception of it bogs a little off idle.
Twice now, when the engine gets a little hot, it runs terribly. Yesterday, in 100 degree weather in stop go freeway traffic with AC running ( no condensor fan ), it died. Restarted, but was running terribly, and backfired once. I managed to limp 1 mile to a shady parking lot where it died and would not start. I lifted the hood, and let it cool for 10 minutes. Started right up. I turned the AC off, the heater on, rolled down the windows and drove home. It ran just fine.
The car normally runs with the temp gauge at 40%.It was at 60% when this issue came up.
Things I have already done; In tank pump, fuel filter, cleaned throttle body, plugs, cap, rotor, timing belt, new water pump seals, checked for vac leaks,
air filter, plug wires. Added a missing engine ground.

Hi,

Are the spade terminals on your coil clean and tight ?

regards,
Peter

When I drove a '92 940T it had a similar problem. If your model has a FI temp sensor (with 2 terminals-not the gauge sensor) I would change it straight away. - Dave

Hi Dave,

I agree with your assessment of the issue.
It sounds like the engine is running too lean during the warm up stage and higher temps.
I think we both are ignoring the AMM idea or connector possibility, as that, would make it too easy.
I only bring that up because he said he limped it home, yet, it ran fine with the heater core in the mix!
AMMs don’t usually work that way.

The ECT Sensor may not be in sync with the engines heat range or there is a condition being thrown into the engine beyond the fuel systems control.
My thinking points me to the intake manifold gasket leaking.

The leaking or the sensor would leave the engine lean and it would exhibit low power symptoms.
Since the engine dies and runs terrible on it way up to a “hot days work” both are definitely suspect.

If it were me, I would pull back the intake manifold to give me access to both, especially the connector pins to check for corrosion.
If it has a tattered and crumbling gasket, that would be enough to let me yell, uncle!
Take a measurement of the sensors ohms and compare it to another one, in my stash, at the same temperature.
One can use the chart in the Bentley to see if it’s even close.

Since he says the car has been neglected, doing all of the above is good idea to get them inspected.

Winter is coming and if things are lean now, at one extreme, it’s only going to go the other way.

Coughing on a cold morning is not the time to be bent under a hood, shoving in the ole’ starting fluid. :))))

Phil

Thanks for the tips guys.
I will
1. check integrity of coil terminals
2. remove intake manifold, check coolant temp sensor, replace gasket
( I have a cts for a 90 model, I will check to see if it is the same)
3. Test throttle switch

An easier, cleaner way to investigate #2 is to measure the voltage at the ECU where the engine coolant temperature sensor is connected, watching it start off from cold start and drop as the engine warms. The voltage appears at the blue wire to pin 2 of the ECU. Pierce the insulation with a needle, or open the connector if you prefer.

Compare this voltage to this chart. More notes about this appear in the 7/9 FAQ, but the object is to prove the ECT or its wiring is the culprit before disturbing what might be crusty connections under the intake manifold.



The ECT for the 1990 (LH2.4 or 3.1) is black and wired differently, because it has two elements inside referenced to the brass housing and head, but it will work the same as a replacement for your single-element LH2.2 (blue) sensor. Not the reverse, though.

Yes, the chart is labeled for LH2.4, but the resistance curve of the blue sensor you have is the same, and the voltage conversion similar. If the voltage measurement seems daunting, you can fall back to the static resistance readings most do, but for those you must turn things off and disconnect the ECU.



Then again, if you'd rather pick up a wrench than a multimeter, it is a usual assumption a new-to-you 1988 Volvo could benefit from a good cleaning and new gasket on the intake side.

The sensor can be changed with the manifold in place using a 19mm deep socket on a 10" 3/8" drive extension if you take the AMM plumbing out of the way. Not much coolant is lost if you have the new sensor ready to install.
--
Art Benstein near Baltimore

"I lost one dream /It was in mint condition /In my sleep"

Art wrote--"Not much coolant is lost if you have the new sensor ready to install." True. With the reservoir topped up and the cap on and a cold motor there will be almost no loss of coolant. - Dave

Hi Dave and Art,

I was going to post earlier but I got way laid by the wife to go garage sale shopping.

I was going to add to use a piece of thin “Sharan” wrap under the reservoir cap to seal of the incoming air into that bottle that can come through the cap.
The only amount of coolant I get is right upon the initial extraction of the sensor from mostly it being wet. As I remember nothing ever hit the floor as I stared back into the hole. It’s amazingly small and deep in there.
That makes it pretty hard to start gulping fast down there with the pressures of equilibrium effect going on.

Nice chart there Art, with the voltages on it. I will be saving that one!

Phil

You guys have given me all kinds of good info, and direction to go in.
I am taking a vacation to see Philadelphia, but when I get back, I will resolve this issue whatever it takes and let you know what the issue was.

By the way,I just had a 3 day weekend and decide to replace the very noisy fan ,motor.
Wow, even having done this before, this is the most difficult job I have done on a 240. Worse than removing an engine. ( Stabbing an automatic 200 miles from home is a close second though ). I think I made every possible mistake. I even put the motor in backwards. ( though I caught it before I put anything back together ) If anyone has ever put one in backwards and put everything back together, I really feel for them.

Thanks guys.

I think I made every possible mistake. I even put the motor in backwards. ( though I caught it before I put anything back together )

This is why Steve Jobs made the iPhone - so you can take pics each step and not have to bother with hand drawn diagrams and notes.

The replacement motor looks nothing like the original motor, and can be installed 180 degrees opposite of correct.
A picture would tell you nothing.
Rotation verification is the only way to avoid a 50% chance of a disaster.

And you can read for an hour on that subject as well: http://cleanflametrap.com
--
Art Benstein near Baltimore

"Your fly is undone," was Tom's zippy rejoinder.

New development. Got back from my vacation and started troubleshooting again. Decided to check my newly installed in tank pump.
Nothing. Removed pump assembly and heard a noise like a plastic ball hitting the bottom of a gas tank. Two week old Delphi fuel pump was frozen up. I previously had a pump that was bad out of the box. I have lost confidence in these pumps. Does anyone make a good one at any price? Doesnt make me feel good about taking a long trip in a 240 powered by an unreliable in tank pump.
Lessons learned;
1.You can not assume a new part is good. 2. Having patience while removing the sender / pump unit is better than having to remove the tank to get the float out.

Burco,
Some tanks have 2 to 5 floats bouncing around.
I've fashioned a hanger to fish a few out in my
day. Some folks use the fish tank fish catcher
net style.

Joseph

This one conveniently dropped outside the fuel pump "ring" where it could not be seen!

Dave, you can read for an hour about tank pump troubles here: In The Tank

Been a long time now since I've had one fail, and I check them at each oil change. The one "brand" seemingly responsible for this lull in tank pump problems is the Airtex E8778.
--
Art Benstein near Baltimore

When a clock is hungry, it goes back four seconds.

Check the Bosch connector on the ECT sensor for a missing or loose U shaped spring.

Andrew