irratically unstable engine surge or stumble

I can't figure this out. I own a 87 240Gl B230f engine. LH 2,2. My car seems to have a ever more consistant idling problem. keep in mind the syptoms are are not always there but here's the jist of it. Usually at first start up the engine runs fine but anywhere from 20 minutes to half way in the day( or sometimes not at all) it starts idling irratically usually it surges to a higher RPM first say 2000 but then will drop below normal RPM almost or sometimes stalling and and then back up to higher RPMS. On other days it will be running fine and will just cut out with any warning while waiting at a light. At times it will also surge or hesitate off idle at highway speed. Usually once the syptoms start the car continues to run like this all day until a nights rest. Sometimes the car will be fine but systoms always appear after I engage but not limited to the air condition. Today i pulled a coolant thermostat senser from a junkyard and I installed I thought my trouble was over as the car showed no problems even with the air on until half way into the day when it started again. The troubling idle condition seemsto have lessened in intensity a bit but the car still surged and stalled at times. i checked the fuel pump relay and it had a date stamp of 2004. Just for the hell of it a sampled another relay but still the same results. While at the yard i picked up but did not install a fuel pump(by fuel filter under car) and a fuel regulator. I'm waiting for more advise before trying these items. Any suggestions?

peter

[Peter D]

When the car appears to be OK listen in the fuel filler so you recognise the sound the in Tank pump makes. Now next time she pays up leave her running and listen for the pump if she is silent there is your problem Either the supply to the pump ot the pump is intermittant. However having said that once the pump is running they normally keep running put can fail to start at power up. There is also another possible cause. Where the electrical connection go through the Sender Unit plate corrosion gets under the seal between the nylon insert and the metal top and expands and cracks the insert sheering either the pump power line of the fuel gauge signal or both I have seen this cause intermittant operation of the pump. However if the pump is not starting and it has 12V at the feed then it is sender unit out time. This is not easy and often the pipe are co corroded they snap off then you try to remove the pipes and you have to remove the locking ring. Be prepared a replacement complete sender unit availably only from Volvo is £248 + vat. a replacement pump is £38 form eurocarparts. Let us know the outcome. Regards Peter

[Clifford Pope]

If you do get to the point of facing corroded pipes just on top of the sender unit, I did a very satisfactory bodge by cleaning it all up and encasing all the metal pipework in epoxy resin.
Try pouring a bit of boiling water over the ends of the nylon pipes before trying to pull them off the steel pipe-ends. If you have to use force you are liable to twist the steel pipes to pieces.
Pin-hole leaks here can let air get sucked into the fuel.

Is yours the model with an Idle Air Valve under the inlet manifold? I find that the major and regular cause of poor idling. It seems to carbon up quite easily and cause sticking at high idle. Easily cleaned with petrol or WD 40.

[dave_tps]

did you ever get to the bottom of this,

i have a problem similar

[dave_tps]

did you ever get to the bottom of this,

i have a problem similar