Volvo 850 Made from 1993 to 1997, this Volvo line was available in both a wagon and a sedan, both with were graced with several trim levels.

850 with rough idle / high idle

Old 11-04-2009, 09:49 AM
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Default 850 with rough idle / high idle

We've been driving a Volvo for the last seven years. Finally had to retire our 740 because it was having issue after issue... when we had an electrical fire in the dash, I drew the line and told my husband we needed something new THAT DAY. I've regretted the urgency since then, but what can you do? Cars can't catch fire when they contain three small children.

So we bought an '95 850 Turbo that we knew needed some work. So far we've spent $3100 on the car itself and $1700 on repairs. The check engine light was on when we bought it, and independent Volvo specialists replaced EGR valve and fixed inoperative odometer. We're ignoring the issues with ABS controller at the moment.

It was out of the shop for a week before the car started running roughly when cold and occasionally surging to 2000+ rpm at idle. Then the CEL came back on. OBDII codes indicate misfires on several cylinders and general misfire code.

Yesterday I replaced the distributor cap and rotor, but if anything it got worse. Plan to tackle the spark plugs today. Possibly running rich -- we're intermittently smelling gas, but seems like mostly in the cabin, and mostly since yesterday. Very poor mpg last night. The surging and rough idle happens often now, and is no longer limited to when the engine is cold.

Because of the surging, my husband suspects the IAC. He tested the voltage across the plug, and he says that the control voltage is the same as battery. That's not right, is it? What sensors feed that control voltage, and how can we test them?

I hate this car. I miss my 740.

Thanks in advance.... Sharon

Last edited by rosesforlily; 11-04-2009 at 10:20 AM.
Old 11-04-2009, 01:53 PM
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When he does the plugs, which caused the misfire code on my 94 850, make sure he uses either OEM or Champion Copper Plugs. They are the only plugs that these cars like.

As for the surging, I would look for a vacuum leak. The IAC really does not do much unless the car is under load, like when the AC is on.
Old 11-04-2009, 02:32 PM
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Thanks! I bought the Champion coppers yesterday -- had previously read on here that they were my best bet.

I'll let him know about the vacuum leak. It runs roughly all the time, but only surges when in park/neutral. Are you saying that the control voltage for the IAC should be same as battery, then?
Old 11-05-2009, 09:23 AM
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Check the coolant temperature sensor too. Our 95 Turbo started hard, ran rough and idled high when the sensor went bad. Set a misfire code at first, then no codes. The sensor is on the thermostat housing. It was a cheap and easy fix.

Don't hate the car, the 850 is one of the better Volvo models (in my opinion) If anything, have a dislike for whoever mistreated it before you got it.
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