KA24DE being a piece.

SON240sx Automotive
1

Here’s the run down:

S13 KA24DE that ran great when it was pulled out of the car it originally came in, sapped into a '90
Emissions deleted
Power steering deleted
Intake, header
Second exhaust cam on the intake side
No vacuum leaks, 100% for sure
Timing is bang on… both ignition and cam timing
Good compression

Here’s the problem:

When I first put it in it wouldn’t idle most of the time, it would just stall but would seemingly randomly idle perfectly. To “fix” this I cracked the throttle plate open more, now with the idle air control plugged in it idles at 1900 RPM for 20 seconds, then it will bog down, run really rich and idle at 400 RPM for about 5 seconds, then go back up to 1900 and repeat.

With the idle air control unplugged it will idle at 1500 for 20 seconds then bog down, run really rich and idle at 400 until I give it a bit of throttle, then it will idle at 1500 for 20 seconds again and repeat. If I don’t hit the throttle it will stay at 400 RPM.

It never stalls, just comes very close.

The idling up and down is like clockwork - I’ve timed it and it’s exactly 20 seconds each time… so it has to be something electronic.

I’ve swapped some parts including the ECU, MAF, ignition coil/ignitor. Only one I really want to swap that I haven’t is the CTS, I know it can cause some weird issues.

Anyone have a suggestion? This car is going to be the death of me.

2

I’d be looking at the IAC/AAC valve.

Set your base idle as well.

Cranking the butterfly is the last thing you wanna do. You have an idle adjustment screw.

Edit: It will run rich when it is barely breathing

3

Yeah, what gets me about it is when it’s idling relatively okay at 1500rpm with the IAC/AAC unplugged… what could possibly cause it to bog down after 20 seconds?

The only thing I can think of is the ECU deciding to dump in waaayyy too much fuel… but why?

4

I was thinking the same thing, clean that bitch out with some carb cleaner. or get a new one.

5

When the IAC is unplugged, it’s a dead fuck. It’ll do whatever the vacuum in the engine wants. Suck it in if it can, unless it’s clogged solid.

These things are old as shit. Motors full of varnish and carbon. That stuff is NO good for any motor. Regular oil changes, plugs and fuel filters once a year at least.

Pull out the IAC/AACV clean em up. If you notice a difference, but still not 100%, get a new one. Be sure to clean the passages as well.

Try spraying intake cleaner through the 5/8" hose before the throttle body. Does the car run with it off? Clean the throttle body as well.

6

new intake gaskets?

7

I can not see plenum or intake gasket of any sort.

I could understand if it was steady all the time or changed with the temperature of the motor. But he said nothing like that.

Either way dude, if you can get a smoke machine for it…do it

8

I already pressure tested the intake/manifold, there aren’t any leaks.

I’m going to try some more stuff today, I’ll get this bitch working yet.