I have a 1997 850 with 92k i changed the oil and now the car is running rich. I don't have any computer codes. I have checked the resitance of the O2 sensors with a multimeter (volt meter) and both the front and the rear had simiular resitances. With no codes I assumed the O2 sensors were ok. I then brought it to the dealer and they said it was the mass flow sensor. I ordered the part from OEM volvo parts online (new part) and put it in. Now, with the new sensor the car doesn't start. I have thought about replacing the temperature coolant sensor. I know the plugs are dirty because it was running rich and need replaced but it should start with the dirty plugs. The starter motor runs and the engine goes through the starting procedures but just wont run. PLEASE ANY HELP WOULD BE GOOD.

I just got a check engine light on my 97 854T5 a few days ago; I pulled the(generic)code using the orange ACCRON(sp?) reader and it said P0172(??)- fuel rich on 1st bank(or something to that effect). I cleared the code & 2-3 hours later it came back on!! I don't have any black smoke or bad plugs, just a rough idle at start up(about 950-1000rpm), while it usually idles @ 7-800rpms. I plan to go see my indie mech. this week, but wondering what could be possible cause for this.
BTW, plugs & wires are 4 months old; O2 front sensor is 3 months old; use only Sunoco 93; I upgraded ECU in May(Upsolute reprogram). Can someone give me the site that has volvo basic codes; code was not listed in the Hayes manual!! TIA,BD

have you tried to reset your ECU by disconnecting the battery for a couple of hours, the ecu may need to learn that it has a new MAF sensor installed, who knows, but i know if you change a 02 sensor the ecu needs to be reset.

besides this would be a good time to getr the battery charged from all of the cranking over that you have done.

since the MAF is right next to the coil, could you have knocked the coil lead loose by chance? just a hunch

Dan
97 850 glt turbo

Like previously asked, I too have been wondering why you say that. If it was, you'ld definately have fuel trim fault codes and a check engine light. It's best to use a scan tool to monitor O2 sensors and fuel trim rather than using a VOM. When using a VOM, was the engine at operating temp? A MAF usually doesn't cause that in 850s (rare compared to NEW Volvos) and a MAF shouldn't cause a no start either, the engine should start even with the MAF meter unplugged.
Does it start with the old (probably good) MAF meter? Are you sure that all wires nearby, like the coil wire is plugged in?

Lastly, don't just guess at parts as you'll spend (waste) alot of money doing that. Most shops can only charge you 1 hour labor to diagnose a "no start" or drivability problem SO even if that's $90 (like at my dealer), that's still cheaper than throwing parts at it when you're just guessing.

I did bring the car to the dealer to have them diagnose the problem. The dealer told me it was the mass flow sensor. I know the car is running rich because of the black exhausts gases and the black soot on the plugs. I am thinking i might just have a vaccum leak. If i unplug the mass flow sensor I can get the car to start most of the time. Are there any key vaccum lines that could cause the car to run rich or not start? For now I will try disconnecting the battery and hoping that the ECU needs reset.

you can clean the MAF sensor with alcohol and Qtips, remove teh sensor from the sensor housing withthe two screws on top of the sensor, pull it out and clean the element with only Alcohol, it is platinum.

i clean mine every year with no problem.

Dan

I think that the tech assigned to your car misdiagnosed your initial problem. If your car has a vacuum line going to a fuel pressure regulator on the fuel rail, disconnect that line preferably after running the car until warm (IF you can get it to run) and see if gas is dripping from the regulator. Not all cars have it, changed system in later years but on cars that have the earlier type systems with FPRs, when they fail it's a common reason for running so rich that you see black clouds and if bad enough, it'll flood the engine too. Your engine oil will smell like gas, plugs will be carbon fouled.
A bad ECT sensor will also do that but you'ld get a code, check engine light.

I have not ever seen a bad MAF causing that on an 850, nor do I think that the idea here of disconnecting the battery will help.

well I got the car to start by unpluging the electrical connectors to the injectors and disconnecting the MAF. After getting the car warmed up i turned it off and tried to start it with the MAF attached and it wouldn't. I then tried to connect the MAF while the car was running and the car turned off. I then replaced the engine coolant temperature sensor and tried again and i couldn't get the car to start with the MAF connected. Any ideas on why it won't run with the MAF. I bought the MAF new and put it in last week. Any help is appreciated.

This whole thing started because, you said, "the car is running rich."

How do you know this?