Hello,
We have a volvo 850 cd 2.5 1996 and have a problem in slower traffic - but not on the freeway. The problem is more acute in hot weather and with A/c on.
The engine seems to misfire and knock and eventually cuts out if we cannot get a clear run.
Our volvo mechanic has replaced the leads, spark plugs and cranck sensor - to no avail. Volvo cannot help and the diagnostic reveals no problem.
Anyone else out there had this problem and found a solution.
Best regards
Rory 2009

You may have a leaky intake manifold gasket. Also try cleaning the MAS and check the intake bellows for leaks. If the mechanic replaced the camm sensor for this problem get your money back. It will only cause a no start problem. Once the engine starts it's out of the picture. One other thing is the air intake temp sensor. When it's bad it doesn't close and the engine is always sucking in heated air. This very well could be your problem. Take the sensor out and let it sit at room temp. If it's bad the rod will only be sticking out about a 1/4 inch. Should be about 9/16 inch long. You can always jam the air intake so that it's never using heated air.

haynes manual lists possible cause as a leaking injector.....have them cleaned and replace the fuel filter. might want to replace the dist. cap, rotor, and flash shield as well. Mass air meter could also be going bad.

A tad more info is needed on your problem. Are you in the Southern USA? Watch your temperature gauge, it is staying at normal, is it slow to rise from a cold start? Is the engine fan on when the AC is on?

It sounds like the engine is over heating at slow speeds. Are you using premium gasoline or 87 octane? When was your thermostat last replaced? How about the antifreeze? If the fan is not running at idle with the AC on and the engine warm, I suggest verifying that the engine fan relay be tested.
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My name is Klaus and I am a V ♂ lv ♂ holic.

Thanks for the reply Klaus.
We are in Melbourne, Australia and the temperature guage is ok. We do not use anti freeze and use 91 octane petrol (gas).
I dont believe it is an overheating problem - just the effect of a hot engine on some electric component. Otherwise the car is ok.
Thanks
Rory

Might I suggest a full tank of premium? The regular fuel will ignite sooner with more heat, and actually cause some of the conditions you describe. The 2.5L engine has very high compression and detonation is a problem.

Using Antifreeze increases the cooling capabilities of the radiator and engine and raises the boiling temperature at the same time. Water is not reccomended except for an emergency.
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My name is Klaus and I am a V ♂ lv ♂ holic.

I have not had this particular problem, but some things to check for might be -vacuum leakage, clogged fuel injector, the age of the coil, or the fuel filter etc?
also with the age of your vehicle a compression test might give some answers
good luck
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'97 855na, Mobil 1, K&N, various IPD's and eBay's

Thanks for the reply Klaus.
We are in Melbourne, Australia and the temperature guage is ok. We do not use anti freeze and use 91 octane petrol (gas).
I dont believe it is an overheating problem - just the effect of a hot engine on some electric component. Otherwise the car is ok.
Thanks
Rory

Thanks for the reply Klaus.
We are in Melbourne, Australia and the temperature guage is ok. We do not use anti freeze and use 91 octane petrol (gas).
I dont believe it is an overheating problem - just the effect of a hot engine on some electric component. Otherwise the car is ok.
Thanks
Rory