1990 240sx KA24E, high idle weird ign. timing

[Punk21790]

ok, i just rebuilt a ka24e and have done the cam/crank timing 3 times. i finally have it right and now the ignition timing is giving me fits. when i hjave the ign. timing @ 15deg. BTDC as it says it should be, the idle rpm is anywere from 1500 to 2500. i hooked a vac. gauge up and it is creatin 20 in. of vacuum. but its bouncing rapidly from 20 to 17ish. i have tried many things trying to get this car road worthy..... can someone please help me, if you dont know whats wrong id still like to hear ideas.

[PapaSmurf2k3]

I'm no single slammer expert, but maybe your throttle plate is cracked open a bit, or your idle air control valve is out of whack?

I'd try pulling off the intake tube and looking at the throttle body to make sure the butterfly valve isn't open. You could also check the TPS voltage.

As for the vac... the only thing I can think of is if your cam is out of alignment, or you have an improperly adjusted valve, and maybe (but I've never heard of this happening), something is wrong with your PCV valve.

[Punk21790]

i have my TPS and IAC are disconnected b/c in my maual it says to disconnect the two when doing the ign. timing. , i have checked my tps voltage and it is within spec also. and im thinking the valve sopring is weak b/c i have a book that says a floating vac like mine could be a weak valve spring.

[CaelanSeth]

curious as to if you have found a solution... My idle was a steady 700... I then changed my belts, cleaned my throttle body, and now my idle is all over the place, usually hovering around 2000 rpm, but after it gets hot it bounces around rapidly from 1200 to 2000. I have cleaned my IAVC, disconnected AIV, pinched my air regulator hose, sprayed vacuum lines to look for leaks, ran w/o MAF sensor, all had no effect on the idle...

[mick]

I had this problem............I changed the 3 vacuum lines buried under/behind the steering pump......2 go to the charcoal canister................

I got smaller silicone vac hoses and the idle problem vanished.