940 running help

[clareehunt]

I am no expert and know very little but have a problem with our 940. On wet cold days it starts fine but is really reluctant to accelerate. You can put your foot fully down but it will not gain speed. Sometimes it will lurch into speed or you have to release the foot and re accelerate. Once it has gained heat in the engine it seems to be better. Does not idle well either when all this is happening. It goes fine and the fuel relays have been replaced recently but this problem is getting worse, although it has been wetter lately and I though it was just the damp getting in. Can anyone throw any light on this. It is an auto 940, no turbo, petrol and built 1994(M reg).
Grateful for any help.
Clare

[andykem]

Sometimes, if damp can be a cause of lack of performance, it can be the air filter getting gunged and the damp makes the goo or powdery stuff that the filter accumulates sticky so that the air cannot pass easily.

Way to test is just to remove the air filter, although that will affect the intake airflow too. So, unless you've just replaced it, you could replace it anyway and it's neither heavy technical nor terribly expensive.

Then again, it may be something else.

One other thing worth doing is undoing/doing a couple of times, each of the plugs connecting the various things in the engine bay. There's probably an air mass meter in the air intake, assuming it's fuel injection, throttle switch by something like the 'carb' or throttle body and probably an idle air valve too. As well, there'll probably be at least one temperature sensor or sender. All these things send messages to the engine's electronics and if the connections are iffy, they can interfere with how it all responds.

Regrettably, I do not say this with much authority as I am unfamiliar with tha later 4-cyl engines. But, I imagine that most of the gizmos used on 6-cyl engines are also applied to the 4-cyl ones so as to improve fuel economy and, of course, 'save the planet'!

If after you've done these easy things, there is still the same problem, I am afraid you will have to rely on others, more knowlegable, to advise

Regards
Andy

[clareehunt]

Thanks Andy, that is really good to know. I like the easy stuff so will start with those ideas.
Cheers
Clare

Had a similar problem with my 940estate - it was an air leak into the intake trunking causing ice to form - try checking all the clamps and looking at the trunking itself.
Oh - also try squirting some carb cleaner into the mass airflow device.These gunge up over time and cause the same problem.Hope this helps.

[Magnolias]

I had similar symptoms some years ago on an automatic Cavallier 1600.
It was the automatic choke. It fired up OK, and ran superbly when up to normal temperature - but between those points it was a real pain, stalling, refusing to respond to throttle, leapfrogging along at 10/15 mph etc.

[sheerwater]

This really sounds like a damp problem. The rough tickover coupled with damp would indicate shorting in the HT circuit. As simple test is to put the car in complete darkness and start it. Look along the HT leads for little blue flashes. You would be surprised what a firework display can be seen. DONT TOUCH THE HT LEADS!!!!! unless you want your head imprinted in the bonnet!!!
740/940s were suseptable to shorting if the leads either touched each other or went near metal...i.e. the brake pipe from the master cylinder. Simple answer is to separate with plastic spacers...cut up a washing up bottle and make grouves in it. Slightly more expensive is to replace leads as the carbon brewaks down with age / pulling / vibration.
Also try cleaning up the insides of the dizzy cap. This tends to be ignored as its not easy to get off.

[andykem]

I agree whole heartedly with Sheerwater. Should have mentioned HT leads & distributor cap in my own earlier post.

You could also try spraying WD40 all over the HT leads & distributor too. That always works on my wife's Renault 5! But, I suppose that if it does work it really means you need a new set of HT leads at least & possibly a distributor cap. Try cleaning the cap first though like Sheerwater says.

A set of new HT leads is only about £20, Bosch ones are good.

Another thing that can be checked for no expense is the earthing points that affect the engine electrics/electronics. If they have corrosion that might be having an effect too though quite how or why damp weather would cause it to be worse, I don't know! There are wiring diagams at: http://www.volvoclub.org.uk/wiring/U...%203905202.htm but you need the current user/password from the Driver magazine to access it. In the left-hand index column there is an item for Ground Connections and shows pictures of where they are, which makes them easier to find.

HTH
Andy

[andykem]

It should be this one then you can choose your model.

http://www.volvoclub.org.uk/wiring/index.shtml

HTH