Volvo 240 Running Rich, Why?

gmasters · Post by **gmasters** » 12 May 2012, 07:10

I have a volvo 240 that is running very rich. The catalytic converter is glowing red hot, trying to burn off the extra hydrocarbons that escaped from the engine. I know my Air mass meter is faulty, however I was wondering if this is the only part that could cause this issue? I have gone through 3 Air Mass Meters (Aftermarket) and all of them give me a (121) Air mass meter faulty. The car wont run on idle unless I increase the idle control. Please help with any possible theories, as I need to get my car running as soon as possible.

Thanks,
Garrett

Post by **billofdurham** » 12 May 2012, 12:55

Code 1-2-1 also indicates a possible problem with the fuel injection main relay which is mounted under the right side of the dash behind the glove box.

Attached shows how to check this:

240 Fuel Injection Main Relay.pdf: (91.3 KiB) Downloaded 930 times

Bill.

gmasters · Post by **gmasters** » 12 May 2012, 18:16

That is different from the Fuel Pump relay, Correct? If so is it in the same general area?

Thanks,
Garrett

Post by **jimmy57** » 12 May 2012, 22:43

Have you unplugged the single wire from the oxygen sensor (two wire plug is the heater for the sensor)?
LH 2.4 and LH 3.1 systems are heavily influenced by O2 sensor and a bad one can run you crazy.

gmasters · Post by **gmasters** » 13 May 2012, 07:28

That could be the issue, I am trying to hook up a new oxygen sensor. I am trying to figure out which wire goes where. There are two white wires and one black wire. I am unsure of which white wire is which. Does anyone one have a wiring diagram or a way I could test the wires to see which one would go where?

Also would a bad oxygen sensor cause it to have a rough idle? I thought the oxygen sensor didn't have an influence on the condition until it warmed up,

I am also trying to locate the problem with the 121 code. I thought it was a bad MAF, however Bill you said it could be cause by the fuel injection relay as well. Does the 91 Volvo manual 240 with the 3.1 fuel injection have the main relay that could cause this code?

I am just trying to get down to the bottom of this inefficient running condition, I would appreciate any help you guys can throw my way.

Thanks,
Garrett

Post by **jimmy57** » 13 May 2012, 08:52

The black is the signal and the whites have no polarity, they are the wires to a heater element.
The adaptive fuel trim will adjust when the coolant temp is warm enough for closed loop and when you start engine cold the adapted adjustment will be the basis for injection computations. So it certainly affect it.
Disconnect battery or pull the ECM fuse so the adaptives will be lost and then unplug the sensor lead. Now start engine and see what happens.

gmasters · Post by **gmasters** » 13 May 2012, 15:11

Are you saying unplug the Oxygen sensor after I reset the ECM by unplugging the battery? If not which sensor? Then when I start the car do I keep it unplugged or simply unplug it and plug it back in then try to start?

Thanks
Garrett

Post by **jimmy57** » 13 May 2012, 15:36

Unplug O2 sensor and leave it un plugged and run the car and let it warm up and see how it runs.
The idea is to reset the fuel trim to base values and see if it runs better. It may not run perfectly as a car with a lot of miles needs some fuel trim correction.
If it is still really sick and won't idle then it's not O2 sensor issues.
240's were prone to get cracked O2 sensor tips and the sensor would output a signal but it was not correct for the actual exhaust gas content. There was rarely an O2 sensor code until the car was black smoking and fouling plugs.

gmasters · Post by **gmasters** » 13 May 2012, 18:57

Well technically the car has had its O2 sensor unplugged the whole time. The person I bought it from for some reason had the catalytic converter removed. I replaced the exhaust system and the new O2 sensor along with a new cat back, however I have not had a chance to wire the O2 sensor to its plug adapter. I will wire up the new the O2 sensor and see if that changes anything, however I thought it could be caused by some other part of the fuel injection system because the idle is so poor. To keep it running I have to turn up the idle control valve to where it idles high but does not stall. I am just not sure what would cause this poor running condition. The only code I am getting is 121, which I thought was AMM, however I have replaced it 3 times and I am still getting the code and bad running conditions. Could this code mean anything else?

Thanks,
Garrett