I bought the car in 2001 with 80,000 miles. Shortly after I bought it, when I would come to a stop, the idle would drop so low it would barely run unless you popped it in to neutral. A friend at a Honda dealer suggested I check the Idle Air Control Valve, I bought the factory Service manual. When I pulled it off, the screen was caked with dry soot. I cleaned, new figure 8 o-ring and the car has run perfect since. Recently (140,000 miles) the gas milage has dropped from 24 - 26 mpg to 18 - 20 mpg, with no check engine light on. I pulled the IACV again and this time it was sooty wet. I replace the IACV and the Oxygen sensor and reset the ECM by pulling the proper auxillary fuse. When I pulled the IACV connector to adjust the idle like the book says, the engine immediately dies. With it plugged in the engine runs fine although the idle is a little low at 500 rpm instead of around 650. I will need to smog the car soon. With the decreased gas milage, it may be running rich enough to fail. Does anyone think I'm missing something? Why would the old IACV screen be wet? Thanks for your help in advance! I'm new to the forum and have been reading the threads, you guys rock!

 

You need to clean more than the IACV inlet screen. Clean IACV valve movement, iacv inlet and outlet passages. Clean both sides of throttle plate and throttle bore carefully. W/ IACV disconnected only air for running comes from throttle plate bypass. If plate is too dirty, there's not enough air to sustain idle.

Also check the PCV and PCV hose are clean. A dirty PCV or blocked PCV hose can cause oily vapor to be pulled into the intake and lots of caked oil/crud. Some of this is normal, but if intake is wet w/ oil, the PCV may be blocked.

The idle boost valve function can affect cold starting also.

good luck

 

When you clean all that stuff out, you'll probably want to go through the BASE idle adjustment. Search the DIY section for a post by me about that. You don't just adjust idle, it's a bit of a procedure.

 

Thanks for all the help guys! I cleaned the throttle body good and replaced the PVC valve which was quite gunked up. I reset the ECM just for good measure. Fast idle is good and warm idle is right on at 650 in or out of gear. Thanks again!