• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

1990 240 Poor fuel economy. Lost 80 miles per tank.

milanoliver

Member
Joined
Dec 17, 2015
Location
Odessa, FL
After e recent cold start issue, that turned out to be a bad coolant temperature sensor, my 240 is burning more fuel than before, maybe running rich, IDK.
In the process of chasing that issue, these parts were replaced:
Injectors (IPD);
Fuel pressure regulator (OEM);
IAC (Bosch from FCP);
Also, a few months before, I had new pumps installed, and filter. There're no vacuum leaks.
Before I was doing about 300-330 miles per tank. Now I'm 80 miles short, which is quite significant.

Please help.
 
I would suggest a double check of the coolant temp sensor. You may have a wiring issue even though you replaced the sensor itself. Test at the two ecu and ezk connectors to make sure the wiring and sensor has correct impedance. You can also test the voltage as suggested by cleanflametrap on his site.

The other major factors are the o2 sensor and the air mass meter.

How are the basics like the plugs, cap, plug wires, air filter, and rotor? Also make sure the air thermostat is working inside the air box. Hot air all the time going into the engine can fry the air mass meter which can result in fuel consumption issues.
 
Thanks for your advice. Voltage and resistance was checked in the process. The failed sensor was brand new from Volvo, so we checked everything else but the sensor.
Not sure how to check the O2 and MAF sensors. And I really don't want to just replace them, hoping to solve the problem. I already replaced good parts that were working fine.

Also, no faulty codes.
 
Manual or auto trans? Manual trans '90 is likely LH3.1, known to have ECU failures. I bought my '90 240 for $250 with a dead ECU and they were hard to find at the time. The engine just flooded on attempting to start, fuel pump would run and wouldn't shut off when turning off ignition and removing key. I don't know the nature of the exact problem, but it was fuel related.
 
My 240 (LH 2.4 - 1990) had a broken knock sensor, which triggered no code and it ran ok-ish, just bad mpg.
Maybe something to test. I found out that it was bad via datalogging LH ecu, not something thats practical for most people.
 
Manual or auto trans? Manual trans '90 is likely LH3.1, known to have ECU failures. I bought my '90 240 for $250 with a dead ECU and they were hard to find at the time. The engine just flooded on attempting to start, fuel pump would run and wouldn't shut off when turning off ignition and removing key. I don't know the nature of the exact problem, but it was fuel related.

Auto LH 2.4. Already replaced the ECU, not too long ago.
 
You don't say anything about the precision of your mpg tracking. 80 miles per tank could be lost simply by a leaky plastic float ball in the gauge sender.
 
Back
Top