A.A.C VALVE (IDLE REGULATOR) advice me.

[maik21]

im an owner of a 240sx ka24e motor. 90

and the question is, the aac valve (idle regulator) is active when my rpms is not at idle? my car have a problem... the rpms up to 1100 for 4 secs.. then down to 750 rmps for 4 secs... then ups to first. then go to second... and is a cicle... but.. i close up my hear to the ECCS and before my eng rev to 1100 it have a noise like a "tssssss... metal " and the aac valve idle regulator have a toc and my engine revs up. ... i check all the air conduct .. maf to eccs and the other hose that is before the throttle body that connect to the aac valve and all be ok. ... when i press the gas pedal to rev the engine to 1500, its fine and the rpms are stable....

the problem is when the motor is on idle rpms... i check the switch into the tps and its fine... but when i disconect the switch , the rpms is the same.. its have not a change. switch into tps into on position = switch into tps into off position = 750 rmps...

the ecu not show any warning. it show the code 55 ... i put ecu into real time and it not show any problem. .....

when my motor is on at 750rmps and i disconect the o2 sensor, the rpms change? .. i disconect the o2 sensor and the rpms are the same. its not change.

i have a new spark plugs and are platinum 2 electrode. new spark wires, new cap and rotor. my inyectors are clean by a laboratory inyector for 35 dlls(the inyectors was removed and clean). the resistance into the tps are ok. all the way is with resistance. extra ground to maf and body

and other stuff... the rpms are fine when the motor is cold... but when my motor is at warm temp, it fails with the problem that i show in the beggin. my air regulator (bimetal) that apear that its not working because i disconect when my motor is cold and conect at 10 secs after and theres no change into rmps. ......

i hope that all the users of an ka24e help me with this problem and other users with knowledge(i dont know how to write, but its a word that mean inteligence), help me too =)

[FactoryStock]

Sounds like your engine is hunting - idle going up and down. If you have a FSM there is a diagnostic path in the EF & EC section for this problem. There's also a ton of information about idle problems in these forums.

Just be sure to be thorough in your diagnostics before replacing any parts - don't want to replace good parts and not fix the problem (waste time and money). BTW - are there many 240s in Mexico?

[maik21]

nissan dealer dont sell 240sx and ,when i go to them for a computer diagnostic, they say that my car dont show up into their books of cars. they dont fix cars imported.

[maik21]

what mean EF & EC ?

[FactoryStock]

EF & EC stands for "Engine Fuel & Emission Control System". Do you have an FSM? If you haven't done so, the best place to start is to set your timing and idle. Then check for vacuum leaks before replacing any parts.

The other thing to do is a search on "idle" in the 240SX forums and see what pops up. Lots of good stuff there that might help point you in the right direction.

[TrentS13]

I sort of had the same problem for my 89 ka24e before until I fixed it, but if this is of any help this is what I did.

1) Check for vacuum leaks for the intake system (cracked hoses, missing hoses etc).

2) Cleaned the metal electrodes on my MAFS with rubbing alcohol on a cotton swab. (In doing this process, disconnect the negative terminal on the battery and stomp on the brake pedal ten or so times and wait a minute in order to reset fuel management control).

That was it. Also, I disconnected my IAV because it was making my engine run funny and there are no adverse affects other than increasing emmisions by doing so. I hope that will help you.

[maik21]

oks, i will try it. my maf is cleaned and i do the "reset fuel management control" . i also have removed my iav. all the pieces work properly but theres one that not work and its the air regulator valve(bimetal) but i think that there is no a reason to do the problem of idle drop. the idle regulator solenoid is work fine. i do a test with a ohmeter and it show resistance. and i put voltaje in it, and the piston move down. =) ... what type of air leaks i have to find?

maf to throttle body? the air duct>? only these? i check for idle problems into 240sx forum but there are no similar with my prob.

[FactoryStock]

Here's the diagnostic procedure from the FSM for Hunting:

1. Check exhaust gas sensor: When disconnecting exhaust gas sensor harness connector, is the hunting fixed?

Yes - Check EGS

2. Perform Power Balance Test: When disconnecting each injector harness connector one at a time, is there any cylinder which does not produce a momentary drop in speed?

Yes - 3. Check plugs (and injector(s))

4. Check for intake air leak: When pinching blow-by hose does the engine speed rise (hose between air box and AIV)?

Yes - locate and repair air leak

5. Check EGR valve - press diaphram and check for sticking

END

Your problem may be something else, but this procedure covers the main components related to the idle.

[maik21]

i dont know where is located my exhaust gas sensor.... maybe o2 sensor?

[FactoryStock]

I'm assuming this is the same for the SOHC engine - I have a KA24DE. The EGS is in the exhaust manifold and is a green wire with a black rubber boot.

[maik21]

in the exhaust there are 3 way to gas come out....one go to the conv catalitic, the other go to the aiv that goes to the box filter into the mafs, and the other turn to the intake and i dont know where is go. maybe there goes to the egr. what do you think?

[crxcess]

yes the one that goes into the intake is the egr. the egr is round and disc shaped it should have vacuum hoses going into it. It shouldnt be your problem though, it shouldnt effect the way your car idles, unless its stuck open. but then your car will missfire and stall.

I think your idle problem is a leaking hose too, check ALL rubber vacuum lines in your engine compartment. even the ones between the engine and firewall. and under the intake.

If all are ok then the aac could be the problem. try disconnecting it from the intake manifold and starting the car. It may steady your idle.

[maik21]

i disasembly the distribuitor and check the sensors into it.

[Julio Bro!]

Hello FactoryStock: I have a 1993 SE model with the AIV already removed and I'm having a similar problem . It started after heating problems because of the water pump leaking. After replacing the water pump the idle problem stayed...it's been a week now, I thought it would go by itself.

I haven't check my FSM yet, but is it that same process? What if my EGS has some trouble?

[FactoryStock]

Hey Julio Bro. I assume that your car isn't overheating now that you replaced the water pump. Sounds like the idle problem started when the water pump went bad - yes? Is your engine still running hot? Hope not.

I doubt that the EGS is causing your problem. Just start with the basics - plugs, vacuum leaks, timing and work up from there.

[maik21]

i dont have a egs sensor into the ka24e !!!

[maik21]

in the electrical shematic diagram there is not a egs!! or i confuse but i dont know how to locate it... the exhaust go directly to a egr by a metal hose!

[maik21]

need i remove some thing to get access to the egs ???

[Julio Bro!]

Hey Julio Bro. I assume that your car isn't overheating now that you replaced the water pump. Sounds like the idle problem started when the water pump went bad - yes? Is your engine still running hot? Hope not.

I doubt that the EGS is causing your problem. Just start with the basics - plugs, vacuum leaks, timing and work up from there.

It's not overheating, nor leaking, the system is fine...except that the Temp needle is jumpy. Under acceleration it trembles and goes down, then back up at constant speed or idle...could this provoke the idle problem?

[FactoryStock]

You probably should look into what's going on with the temp gauge. Even though it's not overheating, ultimately most sensors are connected back to the ECU and if the ECU is getting unreliable information, then it might produce incorrect outputs, which in turn may produce an unstable idle.

[Julio Bro!]

I was told that if my Temp sensor is the original one, it may be failing, and even if I'm not sure, it's a good thing to replace it.

I just hope it's not expensive. Have anyone replaced this, is it in touch to a water channel?

I just found out that there may be 2 temperature sensors, one for gauge and the other for computer. Is that so? Where is each and which should I change...maybe both?

[maik21]

well... i change the coolant temp sensor because i think that it was fail. i have a new coolant temp sensor and it cost $30 bucks. the temps sensor that have one wire is the gauge temp.

and the other , that has 2 wires is the coolant temps sensor. it will adjust fuel in diferent temps. =))

if you which to change, you will change the sensor that has 2 wires.