92' 240sx (KA24) runs WAY rich after swapping head. (I searched, no luck)

[ytboy4ever]

Let me start by saying I have searched for hours and have done lots of investigating on my own part, I come here asking questions as a last resort. (Trying not to ask questions that have been answered 100 times before.)

Ok, so here's the deal.

My 240 (KA24DE) runs pig rich at idle, and I'm guessing rich all other times due to the drastic drop in gas mileage. At idle the car shoots black smoke out of the exhaust. It will not idle correctly, constantly jumping between 400-600 rpm struggling to stay running.

Now for some history.

About a month ago my upper chain guide decided to find a home in between the cam gear and the distributor gear shattering the lower timing chain and reshaping some intake and exhaust valves. My father and I replaced the head with a good head from a friend, replaced all the timing chain stuff with good parts, installed some arp head studs and did the ka intake manifold emissions removal according to the write-up posted here on NICO.

Ever since then the car has acted as described above, running rich and not idleing.

Now for the details.

Like I said my father and I removed all the emissions crap per the write up here on NICO. We blocked off the EGR and got rid of everything minus the IACV and it's associated parts. My father suspects that the problem breeds from this, I don't. The FPR sees vacuum from the Intake manifold, the IACV sees vacuum from before the throttle body.

When we replaced the head and timing chain we didn't have a timing light so my dad set the timing by "ear" which seems to be close (the car runs). I haven't tried to set the timing because the idle is so bad, nor have I checked it with a timing light. (Going to buy one tomorrow.)

Now for what I have checked.

I checked vacuum and it seems to be okay. At idle it bumps around with the idle, but at about 600rpms the vacuum is about what it should be (16inHg) and lower when the rpm drops. At WOT vacuum is ~ 0. At 2000rpm vacuum is 20+ inHg. This all seems to be okay so I ruled out a massive vacuum leak being the problem. Maybe I am wrong.

When the MAF is unplugged (i.e. safe mode) the car runs better. I still think it runs rich but it doesn't pour black smoke out of the exhaust and it idles better.

I checked the MAF with a known good one and the problem didn't change. i.e. the MAF itself seems to be okay. Also the car has a S-AFC II, so I checked the input voltage from the MAF with the AFC and it seems okay. A lil over 1v at idle and 4.7v at high airflow.

I replaced the water temperature sensor with a new one, which didn't help.

Just tonight I checked the ECU codes, I get 12 (MAF sensor) and 14 (vehicle speed sensor). I swapped a HUD cluster with an analog cluster a while ago, I wonder if this has anythign to do with code 14?

NOW FOR MY QUESTIONS

1. Could having a S-AFC II trip code 12?

2. Could unplugging the MAF have tripped ECU code 12?

3. Could the S-AFC be bad and sending crazy voltages to the ECU causing the rich condition?

4. Does code 14 have anything to do with running rich and could swapping from HUD to analog tripped code 14?

5. Could the Crank Sensor (built into dizzy) be the problem? Seems like if the crank sensor was damaged the car wouldn't run at all. My father and I didn't replace the Dizzy when we replaced the head.

Where should I go from here?? Should I check and try to set the timing? It seems to me that if the timing is off a bit it might affect the fuel a little bit but not enough to pour black smoke out the back.

I am tired now and can't think of much more, any help would be great. Sorry for such a long post. Thanks in advance.

[ytboy4ever]

bump, any help would be great. Maybe my first post was too long and has scared away any help...?

[turbonola]

i'm new also, and i'm having the same type of problem but i didn't swap the head. i'm gonna be paying attention to this thread cuz i'm trying to figure out what's wrong also.

[ytboy4ever]

i unhooked my S-AFC and it runs fine now. For some reason the AFC was sending high voltages to the ECU. I don't know why and I need to test some things but as for now disconnecting the AFC made it run like stock.

[NISTECH]

What all does this AFC get wired into? I dont have one nor do I deal with them at the dealer.