coasting problem

[Palmer]

Yo guys.

Just noticed something on the 940. When you coast on the move. With the clutch down or in neutral. The revs drop to like 200. Sometimes it picks up really up really quick and is unoticable. But sometimes the lamba sensor light comes on and the whole car jolts and the revs are kicked back up to idle. Also sometimes stalls but fires back up no problemo.....

Its like it doesnt like going from being under loads. Ie driven... To going back to idle. Doesnt do it all the.time tho its weird!!

[The Hooded Claw]

My Saab used to do that all the time (used to throw a P1107 (I Think) fault)

1107 is "Bank 1 Lean" (I think) we changed the Lambda Sensor & it was no Different .... we eventually found the Exhaust manifold Gasket was Dragging in air & causing the Lambda light to come on.

Maybe completely different on the Volvo .. but info worth considering non the less !!

Keith

[gpl1968]

It's time to make yourself a code reader and check for codes (not all trigger the lambda light).
Also check all your inlet/vacum hoses for cracks.

[Daim]

Why coast? The engine has a fully functioning engine brake...!? Doesn't use any fuel until you get to around 1200 rpm!?

Is your idle valve clean? Throttle body clean and correctly set up? Does the throttle body switch click in the right position? Spark plugs fine? Distributor all fine?

All little things to check... Be happy though, that you don't have a P1x Volvo with the 1.8l petrol... When "coasting" it looks like this:

+ YouTube Video

[rippedoffagain]

My money would be on a dirty and sticking idle air control valve. Takes about 10 minutes to remove, clean, and refit on a 940. No special tools needed, just a spanner/socket set (about 11mm if I remember right), a screwdriver, and a £2 can of carb cleaner.

[Palmer]

Originally Posted by rippedoffagain

My money would be on a dirty and sticking idle air control valve. Takes about 10 minutes to remove, clean, and refit on a 940. No special tools needed, just a spanner/socket set (about 11mm if I remember right), a screwdriver, and a £2 can of carb cleaner.

And where would this said valve be located :P?

[rippedoffagain]

Originally Posted by Palmer

And where would this said valve be located :P?

Standing in front of the car looking under the bonnet, follow the main air hose from the air filter box to the throttle body. About half way along, you'll see a smaller hose coming off the big flexi hose. That thin hose goes down to the idle control valve, which is bolted to the side of the engine almost straight down from the throttle body.

There will be two hoses connected to it (if I remember right), one is the hose I just said, that goes up to the fat flexi hose, the other goes to the back of the throttle body. On the idle valve there is also an electrical connector.

Its held in place by a chunky rubber thing, that in turn is held on by two bolts.

The pipes and connector only fit a certain way, so you can't really go wrong, but maybe take a few photos before you remove it just to remind yourself in case you get stuck.

It all comes out nice and easily, and is just as easy to refit.

Once its out, just blast carb cleaner into it and leave it a minute or two. Shake any drips off and refit.

Its easy enough to access, but its even easier if you remove the main air hose and the airbox. But if you do that, then remember to reconnect the MAF sensor, otherwise you'll do like I did and stick it all back together, try it, and think you've killed your car

The first time you start her up after cleaning her nose out, expect her to cough and splutter a bit and blow a bit of smoke out of her exhaust. That's just all the dislodged filth being sucked through and burnt off.

[Chris740R]

If you change the idle air control valve and it solves the problem let me know. I have the same problem. To be honest, they way I drive it means that it gets to the point of stalling very rarely so I'm not too fussed.
I've tried cleaning my IAC valve, it didn't really help to be honest, I haven't noticed any difference.