After 2 attempts at cleaning my idle air control (IAC) using the disassembly method in the FAQ, I had to try something else (or lay out big bucks like I should). The unit checked out fine when I applied voltage, and didn't look dirty, but kept giving erratic idle speeds. I read one post where somebody bypassed the IAC completely - tried that, didn't work at all for me. But by unplugging the intake hose to the IAC at the plastic nipple coming out of the dict feeding the throttle body, I found I could change the idle speed by "starving" the IAC of some air. This led to the following (see photo). Here's what you do (but only if your main thing is the thrill of treading where only a Volvo factory designer-guy has trod before). Go to the hardware store and get some garden hose fittings with 5/8 barbs and 3/4 threads, including a plastic ball valve intended as a stopcock on the end of a garden hose. Oh, and you'll need a few inches of old heater hose to connect to that plastic nipple mentioned above. Slide off the gooseneck hose that feeds the IAC, insert the barb/ball valve assembly, and connect to the nipple. You now have an adjustable restrictor that reduces the flow to the IAC. No, you haven't solved the basic fault (which could be the IAC, AMM, throttle positioner, ECU.....) but for me, it cut the "hunting" range of that erratic idle speed way down to an acceptable level - very calm with only a rare hiccup. Hey, it's colorful, it's cheap, and it got me back on the road in no time.



Andy Crosby
87 744, 485K