lack of power
 

Hi all,
i'm new today to the voc forum, my name is marc and i would appreiciate some help or advice if possiple please. i have recently purchased an 850 estate the 2.5 10v, which seems to be lacking in acceleration and power. i have changed all the relevant service parts, oil filter, air filter, fuel filter, spark plugs but the car still seems flat. i have never owned an 850 before but have had a v40 2.0 which was rapid compared to this. is this common in the 850 to be honest i was expecting a bit more oomph as i have desired an 850 for quite some time. any advice?
thanks.

Well the B5252S engine isn't the quickest out of the blocks, but it should be fairly lively.

Is the car manual or auto?

Check that the handbrake is releasing OK. Also, have a look at the temperature gauge. It should reach the midpoint quite quickly (within a mile or two from cold) and then sit there, regardless of the driving conditions. If not your thermostat is shot, and this can certainly affect performance. Just last week I found out the hard way that a poor connection between the temp sensor and the wiring loom (the connector is hidden behind the power steering tank) was enough to make mine feel a bit stodgy until the engine started to warm up.

If the plug leads, rotor and distributor cap are tired that'll affect things. I've found with my car that these need to be changed every 100k miles or so. It is possible simply to clean up the dissy cap contacts and the tip of the rotor, but if the ones on there have done a big mileage then it's as easy just to fit new.

Make sure too that the tyres are correctly inflated!

Hope that gives a few pointers.

Cheers

Jack

Bloody hell, they don't make em like they used to. I remember the days you could get 4 million miles out of a Volvo between spark plug changes :-).

Capt Jack has nailed it I think.

The only other thing I can think of to check out is the MAF sensor.

Thanks guys i will certinately have a look at the distributor cap and leads as this seems like an easy fix, what about the maf sensor tho' where would i find that? and what sort of difference would it make (what does it do should i ask ?) should the 850 2.5 10v be quite keen on the throttle and how does it compare to the other models like the 20v or the GLT etc? i wasn't expecting a rocket, but a little more give without having to hammer down the accelerator pedal which doesn't do my mpg any good i've noticed.

Sorry forgot to mention the car is manual, not keen on autos as i know they can be a little less responsive.

Evening! picking up from yesterday you mentioned the MAF sensor, what does this do and where would i find it? also is it a costly part?

Cheers.

I second capt jack, I had exact same probs on my v70 10v, after changing the obvious turned my attention to thermostat and ect sensor.
The car was juddering very badly from cold and had slight misfire under load when warm and felt "restricted"
I replaced both thermostat and ect and have noticed a difference immediately, like a new car!

Oops, I didn't read your engine spec properly......... I don't think the 10V has a MAF.

Not a MAF but it will have a MAP sensor, tucked just above the radiator with a couple of electrical connection and a vacuum pipe. There'll also be an air inlet temp sensor in the inlet air trunking between the air filter box and the throttle body.

The ECU has to work out how much air is coming into the engine. On a car with a MAF sesnor system, it does this by measuring air flow MAF = mass air flow. On a car with a MAP sensor it does this by measuring the the Manifold Absolute Pressure and then using information about the air temperature to calculate the mass of air. This in turn is used to work out how much petrol to squirt through for the calculated amount of air. Sounds complicated but it's actually quite straightforward and generally reliable. If something's amiss however, you'll get problems of either under- or over-fuelling and the engine will misbehave.

Faults should throw a code and light up the engine management light.

I reckon a Haynes book would be a good investment to help you find your way around the engine bay.

Cheers

Jack

One last thing - make sure the throttle cable can move freely. They do rust up once the plastic sleeving starts to deteriorate. An easy fix to replace - but if it is a bit grotty try running some oil down the cable first!

Jack

Hi Marc

In the last 3 years I've gone 2.3 T5 to 2.0 20v and then to 2.5 10v - the latter two are nominally same 140bhp output but 2.5 feels much more relaxed in its power delivery - I'd need to check the books but I think that not only the T5 but also the 2.5 have higher gearing than 2.0 - going from T5 to 2.0 I'd noticed I had to work the 2.0 harder (no s**t sherlock!) but that actually it was lower geared so revved higher at all speeds and not actually desperately good on mpg - the 2.5 is far more relaxed and I am seeing much better economy from it than the 2.0. I still miss my turbo though but have another about-to-be-17-year-old to put L plates on for this year and another one in 2014 so it's no turbos for the present.

Nick

Hi all!,

Sorry chaps but i've been working away and never had a chance to thank you properly for your very imformative comments, i've took every thing into consideration and it's nice to know that there are people out there whom really know there stuff!

One thing i didn't mention tho and i don't know if it will play a factor or not, but the service light is illuminated and was when i purchased the car. would this effect the cars performance? if so does anybody know how i can turn it off with out going down the obvious route of garages, some sort of sequence maybe?

Cheers.