'96 850 GLT Surging

[bensr20det]

I did bring home my friends Snap-On Solus scanner. I do not have the European chip so I only have access to the global OBD data. Is there anything that may help diagnose this thing?

[JimBee]

I had this conversation today with an independent Volvo mechanic who has his own shop. I was surprised to learn that the front oxygen sensor can cause erratic engine performance. It works with the MAF, measuring oxygen going out and comparing air coming in then sending that integrated data to the ECU to specify how much fuel to inject. So either MAF or the oxy sensor or both malfunctioning together could cause that.
He said the O2 sensors do last a long time on the 850's (presumably the same on yours) but after 150k miles or more they can start to get flaky. So that's a possibility. The scanner looks for a "lamda" frequency pattern, which is a rapid rising and falling curve. The sensor can also be checked with a multimeter, he said. I think you look for 5 to 20 mv —not sure on that. But I am sure that he said it can cause symptoms. I'd been told the O2 sensors were not that tightly integrated with the air-fuel system. He said that's wrong. the front one is.

BTW: I couldn't bring myself to spend the big bucks for a Bosch MAF so I decided to try the Remanufactured one from JC Whitney. I know, you're all laughing yourself off the chair But, hey, the thing works. A Cardone, I think is the company. Rock Auto sells them, too, and the Autoparts Warehouse. Check out their web site. They use extra heavy solder to anchor the element and some other re-fix that's supposed to make them stronger than OEM. Theoretically, that's doable. We'll see how long it lasts. It was $111.00 plus refundable core charge.

[bensr20det]

Well at this point I'm ready to try anything. The O2 sensor I need to be focused on is the one before the cat right?

[JimBee]

Yup, the front one.
another thing I just thought of: I read somewhere recently that the MAF plug can get loose when the engine is hot on some 850's, I think. That can cause momentary circuit breaks as it wiggles. Suggested remedy was zip tie the cable to stabilize it. Just a thought.

[bensr20det]

My buddy knows the manager at the store where I have bought the MAF and the TPS so I may be able to return both and just get the O2. When I get my MAF back from the store I will add the zip tie. Just for the fun of it I did take off my throttle body and cleaned it up really well, then cleaned all the electrical connectors on the MAF, TPS, and IAC. I tightened up all the clamps on any air hoses in the area and looked for any holes. None of this did any good. I figure if I try everything sooner or later we will get it.

[erikv11]

If you get an O2 sensor, do not get the universal ones where you have to crimp the connectors yourself. Those have worked for some people but not for most. A plug and play (like Bosch 15097) is the way to go.

[bensr20det]

Just called and got the price on the Bosch $139. Just waiting on my ride up there so we can get this party started. If anyone has any other ideas in case this isn't it please feel free to throw more suggestions out there. I still am not 100% that this is it. Because before I started getting this error and it would surge, filling up the fuel tank would temporarily remedy the problem. But was it adding the fuel or just letting it sit that did it. Any one familiar with an O2 sensor acting up intermittently and correcting it temporarily by turning the car off?

[bensr20det]

Alright got the upstream O2 sensor replaced with the Bosch. I hate to say it but I still have the same issue. Any ideas anyone?

[marcusheard]

Could it be your fuel filter or regulator? How about a clogged throttle body?

[bensr20det]

So maybe it's the IAC. While it was doing its thing I unplugged the MAF and there was zero change. Then I plugged it back in and unplugged the IAC. The RPM eventually stabilized around 700. It stopped surging I would say it began more so to sputter but the RPM didn't change much. Also there was black smoke in the exhaust. Then I hooked the IAC back up and the RPM increased to 1000 and continued a small sputter and the is a lot of black smoke. I don't know am I on to anything here?

Here is a video with where we are