lack of power 1987 240 Topic is solved

old n slow · Post by **old n slow** » 19 Aug 2005, 20:22

My 240 wagon with unknown milage over 250,000, has started having a problem with power. When accelerating at any speed, I can feel power intermitently increase and decrease. Not like a "miss" but like I am losing fuel supply or something. Its not a jerky feel, more like a "slow down speed up" sensation, but very mild. I also have erratic idle of about 50-100 rpm. My idle adjustment screw has no affect at all on the engine speed! Help please

LaRy · Post by **LaRy** » 22 Aug 2005, 08:38

In some countries the carburettor was still in use in 1987. Do you have a carburettor?

Guest · Post by **Guest** » 22 Aug 2005, 19:40

No It is injected. I think I've narrowed it down to the O-2 sensor. It actually ran BETTER when I unplugged it! My parts guy said it makes the mixture go to a "medium" ratio when it is unplugged, so if mine was giving a bad reading of too lean, causing the mixture to go too rich, then unplugging it would be a big increase in performance. Cant wait to see how well it runs with a new one but they are pricey! $125.00!!) Ive only got about 145,000 miles on this sensor and close to 500,000 on the car!?

dpauto.com · Post by **dpauto.com** » 23 Aug 2005, 23:35

Guess, disconnecting the O2 sensor is not really a true test and a mistake thinking it's bad can cause you $120.

When you disconnect an O2 sensor, you put that circuit into a limp mode. In return, your fuel mixture will be richer.

Now, let say if you had a bad air mass meter and the engine ran lean (rough idle or lack of power under acceleration), a little of richer of fuel mixture >>> disconnectin the O2 sensor >>> will tense to smooth out the rough idle. Do you get my point ?

You very well might have a bad O2 sensor. But if you want to be sure, get a cheap voltmeter (Home Depot, Sears) and check the O2 sensor's reading. This is how you check the O2 Sensor on your 240. The connector where you disconnect, pull the black rubber insulator back so the connector is exposed but don't disconnect it. Then with your voltmeter set it to DC Volt range 0-20 range. Touch the black probe of your voltmeter to engine ground and the red probe to the O2 sensor connector. Do this at engine normal operating temperture. If the reading on your voltmeter FLUCTUATES from .01 - .09 volt, your O2 sensor is ok.

Regards,
Dave