Ken-chan's car blog

http://www.makemilk.com/pic_hosting/s1495/diy/stripped_screw_removal/stripped_screw_removal.jpg

Just some notes from diy tuning – please chime in and help if you got good ideas.. A bit of mickey-mousing going on unfortunately to get it running since each each setup is a bit different.

Based on KA24DE-T.. I found some cool things about safc 2…

Settings that worked…

I heard of 2 IN 5 OUT being the common one recommended. It didn’t work for me.

1) T25 / N60 MAFS / 370 cc injectors — 2 IN 6 OUT

2 in 6 out worked best. I’ve tried other settings but usually these caused the AFRs to dip temporarily into lean region before returning to around 11 when boosting. It looks like the MAF range wasn’t read correctly and this caused the issues.

My THR points are: LO 3 HI 32

So my low range covers idle and when I let off the throttle.

(going to post actual #’s soon)

*** Note: On 240sx, OBD 1 is easily identifiable since it will have 2 oxygen sensors instead of 3 as OBD 2 system uses. ***

Here is some things that will not cause open loop on your KA24DE OBD1 ECU (years ’90-early ’95):

-IAT sensor (diagnostic item only)

-Rear heated o2 sensor (near cat)

-EGR -> BPT also doesn’t cause open loop

-Disconnection of airbags does not cause open loop (use your brain here to decide what you think is good for you or not – don’t clutter with debates please)

S: Car bogs, sometimes chokes when driving, runs rich.  SAFC cannot seem to subtract enough fuel, CONZULT shows rich mixture always below 0.5v (RICH) for front o2 sensor (OBD1).

** IF YOU HAVE A TURBOED CAR, CHECK THIS POST ALSO REGARDING CAR BOGGING UNDER ACCELERATION.

Replacing front oxygen sensor seems to help temporarily but quickly after it starts causing issues again.  O2  sensor voltage never goes above 0.5v when throttled & released, o2 sensor value seems to stick and not update on conzult.

*** NOTE: ON OBD1 CARS, front oxygen sensor (usually single wire) tends to be responsible for helping ECU control AFR (Air-Fuel Ratios) and operation.  The rear o2 (lambda) pre-cat sensor is usually just used for on-board diagnostics and emissions testing, etc. but doesn’t affect the running of the motor. ***

C: Problem may be electrical: O2 sensor wire possible not having continuity near the firewall.  This is especially easy to spot if o2 sensor seems to stick in value on CONZULT instead of providing feedback.  With heat from exhaust and o2 sensor wiring loose, often the wire isolation can become grounded or connector loose – look for loose broken section from exhaust manifold / downpipe to along firewall

Solution:

Once you find a potentially problematic section – start the car – don’t burn yourself but move wire around and see if you can get reliable voltage feedback from the sensor.  If you find it, turn off motor, replace the bad section of wire along with heat wrap.  Test it.  Afterwards your o2 sensor voltage should fluctuate between 0 and 1 volts (at least past 0.7v) on warm car if you give heavy throttle and let off.

***
Recently I found that when unplugged, the ecu generates steady 0.30-0.31 volts internally on the ecu pin #46 (front o2 sensor) if unplugged / wire cut off near ecu (was testing wideband->narrowband simulation). While unplugged, this causes car to run super rich obviously.

S: When you rev the motor, car cannot go above certain rpm (often over 3k rpm).  It is indication of open loop as far as measuring air input.

C: No signal from MAF or MAF voltage static low ~ 0.2v for example (ecu sees it as error and runs open loop based on throttle input and other sensors).

Solution:

Inspect & replace MAF.

S: Car would bog down with idle hovering up and down especially after car warmed up.

KA-T bad idle – video #1

C: 1 or 2 issues.

Found:

-Clogged IACV (Idle Air Control Valve) sticking on return

-TPS (Throttle Position Sensor) out of spec — was 0.78v @ no throttle — changed to 0.45v

-Another issue was MAF.  Performed diagnostic using SAFC 2 sensor check screen – every time car would bog down – at same time the voltage from maf would drop to 0v and return.  Culprit turned out to be a bad z32 mafs.

After some changes…

Swapped 480 cc injectors, ecu, maf died (0 volts)

ka-t #2 after some changes

After maf and ecu change.. car runs good again.. One thing that keeps coming back since beginning is that I cannot get better than 10 BTDC — it seems to have happened ever since I put on SAFC 2.  It’s not so bad since I am running around 14 psi almost so timing’s safe but it would be nice to get the extra 2 or 3 degrees advance.

*******
Please note that in some cases, I found that the rpm going up and down can be caused by ecu sending incorrect signals.  Also if you replaced IACV with another one but it doesn’t seem to respond or ecu code 25 keeps showing up (IACV mulfunction), check the pins on the IACV connector – if you have swapped the IACV without pulling the manifold, chances are the pins could be bent.  You can check & if they are bent, you can straighten out the pins very easily with a mirror and small screwdriver without removing the iacv off the motor.
*******

LIKE WITH ANYTHING ELSE ON THIS SITE – EVERYTHING YOU DO IS AT YOUR OWN RISK – I WON’T BE RESPONSIBLE IF YOUR CAR DIES, EXPLODES OR YOU GET HURT OTHERWISE – USE YOUR COMMON SENSE!

For those of you who want to verify that indeed it is IACV / AIV that is affecting your idle…

Here is quick and $free$ way to check if the issue with rpm going up / down is IACV / AIV related.  On KA24DE, there is a 5/8″ hose which leads to intake pipe bypassing throttle body.

If you are running stock setup on KA (non-turbo), you will find this is the biggest hose running into your plastic intake pipe coming from the airbox.

1. Unplug the 5/8″ hose end from the intake pipe.

2. Take an old clean spark plug and plug the thick end of it into the 5/8″ hose to prevent vacuum leak and block up the line going to IACV / AIV.  Clamp the spark plug to prevent air leak (see photo).  Make sure that you also block up the nipple on your intake pipe with piece of 5/8″ hose and spark plug again – otherwise, if your intake has a 5/8″ hole that’s open, your car will run very rough (rich) since it will dump metered air.

3. If you were to turn over your car now, the car will stall because throttle body plate is closed and it has no way to get any air since you blocked up IACV / AIV.  So raise the idle rpm by opening up the throttle body plate a bit, simply by adjusting the cable or the stop point on the throttle body spring – both nuts are 14mm – do 1 or the other only.
I would recommend adjusting the cable tension as that is easiest to return back to factory state after testing.

*** Rule: to open up the throttle plate, you must tension the throttle cable – to do that – move both of the cable tensioning nuts down a bit at a time.  Start car – see if it turns over – if not, hold the gas a tiny bit and when it starts let off.  All you need is to get it started and see whether idle is still moving up and down.  If it doesn’t stay and dies, tension it a bit more so that there is enough air going into the motor but not too much or you could reach about 2500 rpm – if so – turn off the car immediately and loosen up the tension a bit.

Once started – check idle – if it’s not moving up and down anymore, you’ve isolated the issue to either IACV or AIV or ECU.  Afterwards, you can set the cables back to factory state and deal with the issue – could take off iacv/aiv and try to clean them, or try spare iacv/aiv if you find them cheap, etc.