Problem starting when cold or damp.. Help

[abulloch]

Well, looks like I solved the problem.... So here's a report in case it helps anyone else.

I decided to go next to the idle valve. (I'd been going through things in the order of the most likely cause of trouble combined with checking the least expensive and most accessible parts first. (So: plugs, distributor cap, rotor arm - should have replaced the plug wires next, I suppose, but I didn't, as they are pretty expensive here in California, and also they weren't showing any signs of hardening or cracking.)

Here's a diagram of where the idle valve is located in the flow chart of parts:

http://www.vlvworld.com/indexframe.html?200/toc.htm

(Scroll a little way down to the first large diagram.)

[This is quite a useful page too: http://www.vlvworld.com/indexframe.html?200/toc.htm ]

This is really quite an easy job which anyone in this forum would be able to do, though the first time round it's a bit of a fiddle (like many repairs - always easier the second time!). No special tools involved, either - just a screwdriver, some q-tips and some cleaning fluid.

For those that haven't done this before, the idle valve on the 1991 240 is under the manifold, on the driver's side of the engine (opposite side from the plugs). It's a metal tube, 3 or 4 inches long, with two hoses connected on the left side, as you lean over under the hood/bonnet from the driver's side: one hose comes up from underneath, the other comes in from the side, and both are clipped on with circular rachet clips. On the right side of the valve an electrical plug is attached - you have to reach round and disconnect it by feel (there's a spring clip keeping the plug attached, so squeeze it and pull at the same time). The idle valve itself isn't screwed on or anything: it just sits snug in a semi-flexible rubber holder which is screwed on to a metal bracket attached to the engine body. So you detach the electrical plug, detach the two hoses by loosening the clips that hold them on (screwdriver) then wiggling them off. Then the idle valve can be slipped out of the rubber holder.

Detaching the hoses can be a bit of a to-do. They get tightly attached over time, so you have to turn them slightly back and forth, and encourage them to move off. Also it turns out that the two metal tubular extensions of the valve that the hoses slip onto have a raised rim at the end which makes for a tighter fit for the hoses, so make sure you've loosened the circular clips enough that they will slip over the rim. This part's a fiddle, but keep on easing them and wriggling them off, and they'll come.

Now you have the idle valve in your hand. You can't take it to pieces, but you can poke inside it using a q-tip (cotton wool on a little stick that you use to clean out your ears!). I dipped the q-tips in some fuel-injector cleanser and poked around as much as I could inside. It didn't look particularly gummed up, but the fact is quite a lot of black gunk came out on the q-tips - I carried on till it was as clean as I could get it (25 or so q-tips), poured some cleaner into the valve, manipulated the parts inside that turn and generally carried on till no more black stuff was coming out. Remember to pull back the sheath that swings back and forth inside the valve (on a spring) and that adjusts the size of the opening on the underside of the valve, and clean well in all nooks and crannies.

And that was it. Re-installing the valve is easy: slip the hoses back on and tighten the clips good and snug, slip the valve into its rubber holder, plug in the electrical plug on the right, make sure everything's in place and try starting up.

Turned out that was it, this time round, for my 240. Reset the engine-light gismo (helpful instructions here: http://www.troublecodes.net/Volvo/ ), and there we are.

[BTW, the engine-light trouble codes were throwing out all sorts of ideas, including that the Air Mass Meter was bad. I read a note from a Volvo mechanic somewhere - sorry, forget where - which said that Volvo themselves tell their mechanics to ignore that trouble code on the 240 from this period. Sure enough, once I'd done the idle valve and reset the diagnostic unit the check-engine light has stayed off - no more rumblings about the AMM, or anything else.]

Thanks, everyone, for all your help - I hope this may be of some use to someone sometime.

Anthony