1999 v70r running rich

[fairmont50]

Have a 1999 v70r with very high mileage that has been intermittently running rich for the last month or so. Previously, disconnecting the battery for a few seconds would take care of the problem for a time but it seems to be a hard failure now. Not seeing any codes or a check engine light so far. I have checked the intake path and thought that I had found the problem a few days ago but it has come back. Swapped out the mass air sensor with a used one that I had sitting around with no change. The first indication for the problem is horrible fuel mileage followed by black smoke and rough running especially at idle. It seems to be getting about double the fuel that is required based on the mileage numbers that I am seeing.

Any suggestions would be appreciated.

Thanks

[Clemens]

have you ever replaced the coolant temp sensor. if it ages it might send wrong data, causing fuel entichment. go blue box (Volvo) or oem on sensors only!

[RickHaleParker]

1. Shorted fuel injector
2. Defective injector driver.
3. Blocked fuel system return line
4. Fuel pressure regulator.
5. EVAP charcoal canister letting raw fuel into the vacuum supply line.
6. Stuck open EGR Valve
7. Defective engine coolant temperature sensor.
8. Vacuum leak
9. High resistance to ground in on ECM.
10. MAF or MAP sensor out of calibration.
11. Defective Oxygen sensor

[chrillew]

When my t-5r was black smoking and running rich, i had a blown intercooler hose.

[fairmont50]

The last time this happened it was a leak in the elbow at the top of the intercooler (exit, I believe). The inner liner had split and it was leaking air through it. It was not obvious, just happened to notice that it was soft.

I have checked all of them except for the coupler at the turbo. Noticed some oil on the outside of the turbo during the last oil change and assumed that I needed to change the o ring and gasket on the drain (again). It would make sense that the coupler has a hole in it somewhere. Picked up a spare today at the junk yard on the way home and will take a look at it later. Hopefully that is it.

Thanks

[fairmont50]

Swapped out the coupler - could not see anything wrong with the original one but decided to change it and the clamps out anyway. Took it on a test drive that seemed promising initially but sometime between 20 - 30 miles in the car started running rich again. Planning to swap out the oxygen sensor this weekend with a used one that has been sitting on the "healing shelf" for 10 years or so and see how that works.

[fairmont50]

I know that it is a bit late on this one but I like to post the resolution for these threads.

The problem appears to have been the oxygen sensor - the used one that was swapped in had apparently not been sitting on the 'healing shelf' long enough to be a working unit. It has since been placed in a proper location. As soon as a new Bosch unit was put in the car started running properly again. After some research, I learned that these typically fail lean which causes the computer to add a @#^%$ ton of fuel. Of course, 1000 miles after the O2 sensor was replaced, the MAF sensor failed as well with similar but much worse symptoms. It runs (almost) like a new car now.

Chris

[polskamafia mjl]

It's always appreciated when people come back and close out a thread! Glad you got it fixed up!