Engine Performance problem
1996 Volvo 850 4 cyl Two Wheel Drive Automatic 135000 miles

I got this car about 2 years ago. When I test drove it it was fine. Two days after buying it I seen black smoke a couple times and then nothing for about a year. Then the black smoke started again. I took it in and they told me it was the oxygen sensor. I haven't replaced this yet, could this really be what it is? The car now puffs black smoke any time there is any kind of hill or anytime I even press on the gas at all. It also loses power when it puffs black smoke. Sometimes letting off the gas and then pressing again makes the smoke go away. I don't want to sink $150 in a sensor if it is really something else. What do you think. Thanks for any input.

Hi xmanandmom,

Thank you for the donation.

An oxygen sensor can cause a lot of problems and black smoke is one of it. However there are also other things that would cause the problem too.

I would recommend getting a second opinion.

Was there any Check Engine Lamp showing?

I paid 75.00 to have a diagnostic ran and they said that it was the the o2 sensor code, but that it could still be something else after that causing it. I don't really want to pay 75 for another diagnostic or 150 for just the sensor if their unneeded.

I knew it may cause black smoke already, but does the loss of power fit too? And could it have been going bad and then fix itself for a year before totally going out?

Hi xmanandmom,

You can get a scan done for free at your local Autozone outlet. Let them check out the code again.

However since you mentioned that it happend long ago and then stopped and suddenly is back, the scan for the code is required to see if there are any new error codes.

Another possible reason for the problem happening after a lapse of time might be due to wiring connections. Some connectors somewhere might be contaminated or loose and causing false signals to be sent to the ECM. You should check if any components might have been dislodged.