91' 240 - Sometimes idle bounces from 1500 RPM down to <500 and sometimes die

[smokin240]

Otherwise the car runs great. But it seems like the idle will dip so low sometimes just out of the blue and the motor tries to recover and it fly's up to 1500 (1000RPM is normal idle) then drops down back below 500. Sometimes will even kill itself it drops so low. If I maintain a rev at 1500 or so for a little bit and let it go, it seems to sort of flush the problem out and maintain a proper idle. But it typically happens when I either first start the car up or drive it hard then quickly shift to neutral - the tach will drop so quickly sometimes it will just die. Any idea's?

[180fan]

could be some gunk on the iacv. some oil vapor got sticky somehow and got to my iacv and caused something similar to that. give that a shot

[smokin240]

My timing was off a little causing the motor to miss a little. I turned it and it stopped the "coughing" and since then also hasn't done the crazy tach thing. If it starts again I'll try what you suggested, thanks.

[smokin240]

Ok, I'm having problems finding the IACV. There's alot of threads on it but not specifically where it is. The "PAIR" as the Nissan Field Service Manual calls it, was removed. Which is that little black box and all it's tubing near the exhaust header and intake filter area, basically just controlled emissions. I have an Injen Cold Air intake, so that's not stock, and I heard that it connects with the stock intake somewhere.

[vancouverbc]

its by the firewall on passenger side. the idle adjustment screw is part of it. mostly not visible.

[smokin240]

Wonderful. I've heard of a guy putting a little hole in that rubber hose and spraying some throttle body cleaner or carb cleaner type stuff down in it while the car is running and got it clean that way. He just replaced the hose when he was done. Would this work you think? And it is that rubber hose that I'm looking at under the IACV right?

[vancouverbc]

The iacv is held on by four 10mm bolts. 10 minutes to take off. no idea why he drilled a hole in hose. he could of just taken the clamp off the hose. When you see how much crap is in there you will be happy you did the job properly. If you are not familiar with staple fasteners, practice on a plug that is more accessible.

the pic shows the iaa unit. the labour intensive part is that you have to remove the epoxy off the brass screw(not in pic) to get access to piston and spring. the piston will be covered in gunk. you may be able to clean it by spraying in the aac orifice. the aac solenoid comes off easy . two screws.


Modified by vancouverbc at 9:45 PM 7/13/2006

[vancouverbc]

If you just want to spay in hose. this is the hose. It is delivering air from the air filter.

[clinthicum]

You've got a bad ground wire at the MAF....reground the electrical connections and you'll be fine. Good a gold !

Chris L.'90 S13 (sold) 215k miles