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I sware... its posessed.

937 Views 11 Replies 7 Participants Last post by  Simon Linton
I have posted on Brickboard, and didnt get a straight answer, no one at Autopia knew... so I came here. Heres my story-

I have a '94 850 Turbo w/ 130k miles, its in good condition but needs an o2 sensor, and a timing belt(never been changed :eek
my problem is this...

Every time I cold start the car, idle is pittiful it just sits idling unsteadily and is very rough. Its hard to hear this, you just feel it. When reving it almost sounds like a small miss.

After driving the car around for about 5-10 minutes (depending on temperature) it really smooths out, after about 15 minutes its perfect, like nothing is wrong. Starting it warm, it runs great from the get go, cold starts suck.

I have tried a fuel system cleaner, only ran it for about 30 miles and its a LITTLE better... but still horrible. Any ideas what this could be?

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I would buy new spark plugs and see if that helps. (couldn't hurt and not expensive). Plug wires also detoriate with age. How many miles are on the car? Does anyone know if there is an auto choke on 850s? If that wasn't functioning it would definately display those symptoms.
Spear, thanks for your reply. The car has 130k miles. I don't know about the auto choke, and I will try new plugs and wires maybe this weekend and see if that helps.

The puzzling think is how it just cures itself over time...
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Forget the plugs. Replace the O2 sensor. When they go bad, an 850 will not run as well as it should. Since the ECU is not receiving information from the 02 sensor, it is being conservative with the fuel mixture. Cars require a mixture that is richer when cold and your engine is not getting it because your 02 sensor is out. While you are at it, might as well put in a new timing belt. You can either pay the mechanic now or pay him big bucks later.

Sounds like SCFrost has had some experience in the matter

Take his advice, sounds right!
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Yes, whatever you do, change the timing belt ASAP, you probably already know this...hence the eek....but Do It soon.

Yeah it sounds like an 02 sensor problem.
Finally, an answer that actually makes sence! haha Well I called a local mechanic today after your reply SCfrost... he said that sounded correct to him.

I now have a project this weekend-

1) Change spark plugs
2) Change plug wires
3) Change o2 sensor

Again.. a huge thanks to all of you who helped me resolve this matter, I will keep everyone posted on how it turns out! Thanks!
There's also a temp.sensor in the housing of the thermostat. This reads the (ofcourse) the temperatur of the coolingfluid. When this sensor is broken you will also experience bad start-up and unsteady idling. I have had 2 850's and on both of them this sensor broke down.... Just a thought.
All of the above sounds good. BUT there is yet another thing to do...

In my 850, once the oil gets some age to it and begins to loose it's properties, I will have a rough idle until the lifters pump-up. I've gone to Mobile 1 0W30 a year ago and never had the issue since. With 130K miles on the car, some engine wear is going to be present. This wear and old oil will cause some roughness.

Well guys, I finally took it to a mechanic who specializes only in Volvos. All he replaced was a a few Turbo hoses that supossedly had holes in them, and the plugs and wires. He said that the o2 sensor is bad, but it wouldnt cause the car to act like this. I am extremely skeptikal it will run right, but I go to pick it up today. Could these few things have been my problems?

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It all adds up. The ECU can do strange things...
Get the throttle body cleaned as well, the tolerance on it are extremely tight and muck builds up to cause the symptoms you describe.
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