Ok guys,

My 940 B200F saloon has had this problem for a couple of months now.

When I start the engine, it revs up to 1500rpm for a second then falls to around 600rpm but idles roughly fluctuating between 500 and 700. Occasionally when driving, the rpm falls to 300/400 and it idles very roughly (i suspect this is the throttle switch not contacting, although it clicks whenever the throttle is closed) and sometimes after high speed running (highway) the revs stay at 1500rpm.

Also the engine temp guage is not reaching normal temperature (it used to be exactly 1/2, and never used to move) now it only reaches about 1/4 on the guage. I've replaced the guage temp sensor with one from a B230K, but it is exactly the same.

There isn't much diffference in mpg, and I checked the spark plugs, they were clean/white deposit around the electrode.

Also the main fuel pump is noisier than ever, not much, but noticeable when waiting at traffic lights.

I've looked at many possibilities (changing FPR, main fuel pump, ECU) all seem too expensive if it turns out to be something simple. I thought I might check with you guys, any info would be much appreciated because I don't want to get rid of my lovely Volvo.

Also, has anyone swapped a 200F engine for a 230K engine, would the ECU from the 200F supply the correct amount of fuel, etc. for a 230 engine, this because I have a 230K engine in my garage and are considering a swap.

Many thanks everyone.

Dangerous Dave

Hi, I have had this problem twice on the B200FT and both times it was down to a leaking inlet manifold gasket. It might be worth having this checked out!

My thermostat broke recently causing the car not to warm up properly. It cost me a total of about $15 for the new thermostat and o-ring, and rougly 4 minutes of my time to replace.
--
'93 945 turbo. A big comfy box.... and a '90 Mazda 626 GT turbo, 16psi on upgraded turbo and a bunch of other mods.

Dear Dave,

Good p.m. and hope this finds you well. I suspect the Idle Air Control Valve, mounted on a bracket next to the intake manifold, needs to be cleaned. If it is dirty, it will stick, and produce wildly variable idle speeds. See the FAQs (under FEATURES, above) for the procedure. Use carb cleaner to flush out the valve. As cleaning involves minimal cost - a can or carb cleaner - and a few minutes to remove and replace the valve, this is a good plact to start. The valve is easy to access.

You might need a new thermostat. That, too, is not a very costly part. Read the FAQs carefully, as you want to make sure that you do NOT install the new thermostat upside-down.

I know little about engine swaps. I'd think it advisable to get an engine control computer (ECU) that matches the engine you want to install.

Post back to report how things have gone.

Yours faithfully,

spook

Suggestions:
-See the 700/900 FAQ for instructions on how to test your throttle position switch. It appears that it might not be making continuity at the "idle" position. Just because it clicks is no guarantee it works.
-Clean your throttle body.
-Change your thermostat, which might be sticking open.
-Your in-tank pump might be failing, or the bottom pickup hose might be split. If the noise is worse when the tank is half full or less, then these two are the likely culprits.

The ECU, etc. have nothing to do with the above problems.