iacv-aac cleaned / still idle high / hunting...

[kirk]

Hello,Sorry for first post. And sorry for another idle issue question for the 240sx

I am having trouble with high idle after the car has already warmed up. 1993 240sx ka24de, with removed Pair valve and pairc solenoid stuff (per p00t's post)

I have followed the FSM for diagnosis of the "High Idle After Warm-up". First step was to test the iacv-aac. I just removed the bugger like so many other posts suggested. Cleaned with B-12. tested AAC solenoid with battery, heard it click/ cleaned it a little. Tested the IACV, 10.2 ohms. Cleaned it, and checked plunger.

Put it all back together, and got it running. Does the same thing. Idles about ~1500 (maybe less) until warm. Idle goes down to about 1000~1100 and my car seems like it stutters ever so slightly. On a rare occasion, out of the blue it will stutter and go down to about 400~500 rpms and almost die and then catch itself and idle back up.

Driving is a different story. During shifts (5speed) or when in neutral coming to a stop, idle will go completely limp like it's trying to idle correctly (1000), but then it compensates and the idle will be high 1500~1700 and stay there for about 15-25 seconds. Then go back down to 1000.

Next was check air intake leak... Didn't check it all THAT good. Just sprayed some B12 around everything, and the idle didn't change or anything.

Next step was to remove O2 sensor and race engine @2000 no load for about 30 seconds. So I unplugged O2 sensor, started car, revved it up to 2000, it sat there fine for about 15 seconds, then the car started missing bad, started to stall, let of the gas, car idled real funny so I killed it.

What to check next???????????????????????02 sensor bad? MAF ground bad? Hidden Vacuum leak??? POS car???

Sorry for the longest post ever in the history of forums. But you guys are about the only ones on the internet with any idea of how to fix these cars.

Thanks for reading and thanks in advance for any advice!!!

KIRK
Modified by kirk at 10:53 AM 7/13/2005

[NISTECH]

Search for MAF [AFM] test and coolant temp test. Check those out and see what you come up with. pay particular attention to connections while performing tests make sure they are clean and free from corrosion.

[kirk]

Thank you!I will let you know what I come up with!

Kirk

[kirk]

Results are in:

FSM coolant temp sensor68° = 2.1-2.9 Kohm122° = .68-1.00 Kohm176° = .30-.33 Kohm

My carCold (approx. 80° outside) = 1.8 Kohmafter warming up car to operating temp = .37 Kohm

There was some green corrosion on the connector, but not much. Scraped it off, plugged it back in. Car is still idling high.

On to the MAF

FSM MAF sensorWhite wire, key on, engine warm .2 VoltsIdle (same wire with MAF plugged in), engine warm 1.0-1.4 Volts

My carWhite wire, key on, engine warm .26~.27 VoltsIdle (same wire), warm 1.6 Volts

Had the car sitting there idling high, went around to check the MAF, as soon as I touched the probe to the white wire the idle went down probably 3-400 rpm (very odd). Also while probing the MAF it would fluctuate erratically. sometimes showing 14 or 20 volts! (this is with a electric multimeter)

So I'm pretty confident that the coolant sensor is ok.I've still got some reservations about the MAF though.....

I will go out and remove the MAF from the car right now. Maybe in the meantime I will get some more feedback.

Thanks for the help,

Kirk

[kirk]

Tested ground wire on MAF, was getting .03 Volts. So I added a ground wire to the intake. Runs a LOT better. Seems to have removed my miss/stumble.I'm still getting high idle.I was going to unplug my TPS and try to set my idle lower, but there is no plug going to the TPS. All I see is a black rectangular box on it with a black wire loom going underneath it. I guess next step will be unplugging it and checking the voltage sweap on the throttle body, then setting my idle lower if possible....

[kirk]

Disconnected TPS.Tested sweep.

FSMthrottle pedal released 2 Kohmpedal depressed 10 Kohm

My carpedal released (idle) 10 Kohmpedal depressed 2 Kohm

Interesting.......

So I warmed the car up. Killed it. Unplugged TPS. Started it back. Idled at 2,000 Rpm!!!! Adjusted idle screw completely shut. Was idling about 900 and was still missing/doing odd idling.

So, I guess my TPS is backwards? I'll do some more research.

[kirk]

OK. no more work for the day.The only thing that I can think of that is left that is bad is the IACV air regulator. I'm thinking that it is broken and is staying in "cold engine" mode, allowing air into the intake past the throttle body.

I hear that the only way to change it is to take off the intake manifold.

So I guess I will do that tomorrow unless someone can give me any other ideas.

Kirk

[vancouverbc]

"Unplugged TPS. Started it back. Idled at 2,000 Rpm!!!!"

idle should fall 50 rpm when you unplug tps.

[NISTECH]

Your Idle air control is trying to drop the idle as low as possible. You have a vaccum leak or a stuck open FICD. with your screw all the way shut use a pair of pinch off pliers and pinch the hose going from the intake tube to under your intake manifold. Does the car stall out?

[kirk]

Car is cold, but with idle control screw all the way in (tight), and I pinch the hose going from the intake tube to in between the intake manifold, the car's idle gets real low.

To answer your question, yes.

So is my FICD bad? Or my air regulator??

Thanks for the help!

[kirk]

I can unplug my FICD and the car will start and idle "normal" (this is with the idle screw all the way in.With it unplugged, I can squeeze the hose and the car will die if I keep it held.Plug it back in and there is no perceptible difference in anything.

[InsanityInc]

Disconnected TPS.Tested sweep.

FSMthrottle pedal released 2 Kohmpedal depressed 10 Kohm

My carpedal released (idle) 10 Kohmpedal depressed 2 Kohm

Interesting.......

So I warmed the car up. Killed it. Unplugged TPS. Started it back. Idled at 2,000 Rpm!!!! Adjusted idle screw completely shut. Was idling about 900 and was still missing/doing odd idling.

So, I guess my TPS is backwards? I'll do some more research.

That's what I thought too, but the FSM actually just tells you to measure the wrong terminals. If you measure the other two adjacent terminals it reads correctly.

[kirk]

Awesome! Thanks Insanity!!

I was pretty sure that my tps was hooked up correctly. (I wouldn't think it would run with it backwards)I tried to check the voltage on the white wire with it connected and the ignition on, but was unable to get my tester probe in there, and I don't have a T-pin laying around.

Another question:Does the whole IACV assembly (FICD, AAC) and the Air Regulator share the same vacuum line (like parallel or in line)? The same one that runs off of the intake tube? The same one I was pinching? Or when I pinch that line, is it just supplying air to the air regulator?

Could my FICD just be bad?I hope so, because it is a whole lot easier to get to!!!!

[vancouverbc]

I think you squeeze the 1 inch rubber hose a few inches from the iaa unit. The intake tube is made of metal and goes under intake manifold.
Modified by vancouverbc at 6:42 PM 7/10/2005

[kirk]

Are you talking about the rubber hose that goes from the metal tube off of the back of the intake and down below to the bottom of the IACV assembly? Then no, I haven't pinched that hose.... Great idea though! Since that would rule out the Air regulator (if indeed the air regulator is before the IACV, and they are in-line).

I have A/C on my car. I haven't even turned it on during this whole process. So the FICD JUST controls the high idle when the A/C is on?

I see if I'm able to pinch that line or not and post the results (after lunch of course! )

[vancouverbc]

"I have A/C on my car. I haven't even turned it on during this whole process. So the FICD JUST controls the high idle when the A/C is on?"

I think it also provides fast idle for few seconds when car first starts. I don't have a/c and was thinking it does nothing on my car but i was wrong.Yes, i think you are right about air regulator being in line.

"Are you talking about the rubber hose that goes from the metal tube off of the back of the intake and down below to the bottom of the IACV assembly?"

yes.
Modified by vancouverbc at 8:01 PM 7/10/2005

[kirk]

If the FICD controls cold high idle, then it definately works. Just cold started my car, and it idled about 12-1300, and then slowly idled down to about 1000 (this is with the idle screw all the way in). I'll test the A/C later.

I managed to pinch off the line just running to the IACV unit, and the car started to idle real low to the point of dying, just like it did when I pinched the main line off of the intake tube. So I'm pretty much confused.

I'm going to go drive the car right now and see if I'm able to drive it to work or not. Might have to get back in the mighty NEON

I hope I don't have to take off the intake manifold of this car. It will be a learning experience though!!!! Might even post some pics and do a walkthru.

~Kirk

[kirk]

Just drove the car. Seems to drive fine.It will still do some high idling around 12-1300 when taking it out of gear and coasting, then it will go down to 900-1000.

I hope leaving the idle screw all the way in will have any adverse effect on anything till I can find exactly what my problem is.

Thanks for the help!

[vancouverbc]

test the ficd solenoid by hooking up to 12 volts. test for 12 volts at plug and test harness continuity between ficd solenoid valve terminal b and ecu terminal 33. may as well check for codes as well.

[NISTECH]

If your idle started high when cold and slowly droped down your FICd is working correctly. Also the fact you could pinch the line after the FICD once the car was warmed up and it died points to your problem being at the IACV/AAC valve itself.

[kirk]

Thanks for clearing things up NISTECH!!!

Is it possible that I didn't clean it well enough when I took it off the first time?

"Cleaned with B-12. tested AAC solenoid with battery, heard it click/ cleaned it a little. Tested the IACV, 10.2 ohms. Cleaned it, and checked plunger."

Could it still be bad even if I was reading 10.2 ohms? Is there another way to test it?

I'm going by Nissan today after work to pick up a new cap and rotor, and will ask them how much a new one is.

THANKS again for the help NISTECHYOU'RE THE MAN!!!!!!!!!!!!!!!!!!!!!!11!!!!!11!

[vancouverbc]

question: How can AAC cause high idle? Does this imply aac solenoid stuck open? if problem with power or ground it would just stay closed, right?

make sure you have 12 v at aac and that there is continuity between terminal f and ecu terminal 113. terminal "f" in an 8 prong connector at front passenger side of engine beside tps connector. many people mention a bad ground in relation to iaa . i don't know how you supply second ground.

Testing the AAC(auxiliary air control):

A. Check overall function1. start engine and warm it up2. check idle speed- should be 700 -+ 50(if no good, adjust)3.perform self-diagnosis. make sure code no.43is not displayed. make sure that throttle sensor is not in"fail-safe" state.4.disconnect throttle sensor harness connector5. if idle speed drops, INSPECTION ENDS.6.if idle speed does NOT drop, GO TO B.

B.Check Power Supply

1. stop engine2. disconnect aac valve subharness connector3.turn ignition switch to "ON"4.check voltage between terminal "e" and ground.5. battery voltage, go to 'C"6. if not battery voltage, check harness connectors, 10a fuse, harnesscontinuity between aac valve sub-harnesss connecot and fuse

C. Check output signal circuit1.turn ignition switch "OFF"2. disconnect ecu harness connector3. check harness continuity between ecu terminal 113 and terminal "f"4. continuity should exist


Modified by vancouverbc at 12:46 PM 7/11/2005

[vancouverbc]

Ground seems to be supplied by ecu to control when aac is on so a second ground would have the aac on continuously as far as i can see.

2 wires from AAC solenoid(yellow plug)(my 1991 240sx):

First wire: Red/white from solenoid to connector at front of engine. changes to light blue and goes to 113 on eccs unit.

Second wire: red/green from solenoid to connector at front of engine.changes to brown and goes to positve at fuse box.

If found this link :

http://www.zeroyon.com/TheSite/techservice.html (1993 factory service manual for 93 240sx)
Modified by vancouverbc at 2:48 PM 7/11/2005

[kirk]

You are a life saver vancouverbc!That is the same place that I got my FSM from. Thanks!

A.I ran car, unplugged tps, RPM actually went up for a second then went back to same idle. (I did not do self-diagnosis, because I haven't touched the ecu before.)

B.Checked voltage to connector E (with key on this time ) 13.3 (battery was about same voltage)

C.I'm kind of confused on what "continuity" is. I made a wire to run from terminal F to the ECU so I could reach with my Multimeter. The wire was reading .5 ohms just by itself (not connected to anything).Plugged the wire into F and tested Ohms between that wire and 113 (sky blue) on ECU.Read .6 Ohms.

Soooooo........Is that good or bad?????

If continuity exists, check IACV-AAC valve

If NG repair harness or connectors.

WE'RE GETTING CLOSE!!!!!!

Thanks SO much for the help vancouverbc!!!!!

[vancouverbc]

"Plugged the wire into F and tested Ohms between that wire and 113 (sky blue) on ECU.Read .6 Ohms."

That means you have continuity. Continuous/unbroken between 113 and f.Most electronic meters are not zero to begin with so your ohms are really only about .1 ohm. looks like your aav is getting good ground and power and you have mentioned that you got it to click by providing 12 volts. there could be a problem between f and connector at aav. your solenoid could be sticking or your ecu has a problem. i only know a bit about electronics not mechanics so don't weight what i say too heavily:)

ground appears to come in to ecu at terminal 116. you might test from 116 connector to ground to see how many ohms you get. anything over 2 ohms is a bad ground, i think.( be careful with ecu . ignition should be off when testing ecu terminals)
Modified by vancouverbc at 7:23 PM 7/11/2005

[xagna]

I find this thread very education as I am very new to engine work.

Please, can some one explain me these terms?

iacvaacB-12TPSFICD

[vancouverbc]

try disconnecting yellow connector at aav. this will cut power to aav so it should close and lower idle. if you can't reach yellow connector, i guess you can disconnect the wire that goes to ecu. i would not disconnect while ignition is on. if there is no change in idle, you can assume it is stuck open or closed. compare how engine runs before and after. there should be a difference.

i would do the same with air regulator. it provides high idle when engine is cold as does ficd. deprive each of power or ground and observe change.

[kirk]

Great ideas Vancouverbc!!

I was also thinking about the wire running from the sub-connector to the IACV. I think I'll check that after work. I also need to pull the ECU and get the codes before I go any farther. I think I'm getting ahead of myself.

I think the only connector I'm able to unplug will be the FICD. It looks like I won't be able to reach the AAC or the air regulator. But I will try.

I'll let you know what I find out!As a side note, the AICV-AAC from Nissan is $177!!!! OMG!

"I find this thread very education as I am very new to engine work. Please, can some one explain me these terms?"

iacvIdle Air Control ValveLocated on the back side of the lower half of the intake manifold. Allows air into the intake after the throttle body causing the car to idle at a set RPM. This unit is controlled by a solenoid that is activated by the ECU.

aacAuxiliary Air ControlBasically the solenoid that activates the IACV (they are the same thing IACV-AAC)

B-12Berryman's B-12 ChemTool. Best carb cleaner that I have found. Cleans gunk off of stuff. Will take the hair off a cat! (not really!)

TPSThrottle Position SensorTells the ECU where the throttle plate is.

FICDControls the hight idle of the car when the A/C is on, power steering pump is on, high beams are on, etc.

Here is a link that will show you exactly what I'm working on:http://www.geocities.com/Motor....html

This also has some great pics of everything:zerothread?id=109345


Modified by kirk at 9:23 AM 7/12/2005

[vancouverbc]

I would do all the easy stuff under high idle and unstable idle before doing anything hard. ie egr, power balance test, clean throttle, vacuum test, fuel pressure, spark plugs, etc. FSM describes power balance test. This trouble shooting is from mitchels and takes alot of stuff right from FSM.

TROUBLE SHOOTING (1991 240sx)******************HIGH IDLE: 5,8,13,21

UNSTABLE IDLE:

after warm-up:-10,25,2,4,7,1,13,8,3,12,17,18hunting:-13,25,7,8,10

ENGINE STALL:

Cold-9,25,2,4,7,1,17,19,18Hot-15,25,,2,4,1,17,19,18,20On momentary acceleration-9,25,2,4,1,17,19,18after deceleration-9,3,25,2,4,1,13,17,19,18acceleration or cruising-25,2,4,1,8,17,19,18heavy electrical load-6,25,2,4,1,17,19,18While turning-25,2,4,1,17,19,18

Symptom definitions:===============1.ensure fuel pressure within spec2.perform appropriate test in injector malfunction diagnostic chart3.inspect throttle body ports and valves for deposits, wear or plugging4.check for spark using spark tester5.Check idle speed control circuit. 6.Ensure battery is fully charged and maintains at least 9.6 volts during cranking.7.check spark plug gap and fouling8. ensure no vacuum leaks in intake system9.Check fast idle system.10.check egr control valve operation11.Check EGR control valve solenoid operaton.12. check engine compression13. disconnect exhaust gas sensor and monitor change in driveability. if it improves, replace sensor. if not, go to 16.14.Remove canister purge line from intake and test drive vehicle.15.Remove vacuum hose from fuel pressure regulator and monitor for symptom change.16.enter self-diagnosis mode 11 and monitor exhaust gas sensor operation17.check ecu harness connector18.try a good known ecu19.Check ECU power source and ground circuit.20.Check timing belt for proper installation(V6 models)21.Check throttle linkage operation.22.Try a known good airflow meter.23.Check for intake valve deposits.24.Check engine temperature sensor25.perform power balance test

[kirk]

FIXED!!!!!!!!!!!!!!!!

A big thanks to everyone who has posted back to me on this topic!!!!! I couldn't have done it without you guys!!!!!!!! YOU RULE!!

Got home. Let the car cool down a bit. Pulled plug off of AAC. Car idled the same. Hmmmmm.....So I went ahead and pulled the codes on the ECU:

12 - MAFI figured it would throw this because I had unplugged my MAF while it was running.

13 - Engine coolant temp sensorSame thing, pulled when the engine was running. (man that computer is GOOD!)

34 - Knock Sensor CircuitHmmm... come back to that later

45 - Injector leakWhat the heck?!?!!?! OH well.

So I reset the codes while I was in there. And it showed 55. YAY!

Here was my train of thought.1. Air regulator can be ruled out. Car idles high when cold, and idle goes down after warm.

2. FICD is good. When I activate A/C, idle goes up.

3. That leaves me with the ACC. Since I unplugged it and the car's behavior didn't change one bit.

Took IACV-AAC off of car. Tested solenoid again. Read 10.7 ohms. So solenoid is "good"Got to looking at the AICV unit itself and LOW AND BEHOLD THE SPRING WASN'T DOING IT'S JOB!!! The spring had gotten weak over time (I guess) and wasn't pushing the plunger against it's seat!!!! YAY!!! Now how do I fix it? I'm only going to buy a new one as a last resort!

If you ever notice on the same side as the idle adjust screw, there is what looks like an epoxied hole. Well, if you chisel away that epoxy (jb-weld) stuff, there is a Brass screw that holds in the spring and plunger. (see attached pic)http://nissaninfiniticlub.net/...t=500

I thought about how to get another spring that was the same, but then I realized it would be a whole lot simpler to just shim the spring. So I cut one of my vacuum hose plugs (like a cross-section) and this fit PERFECTLY into the brass plug. As you can see in this next pick, the brass plug has a seat for the spring to rest in, and the donut shaped piece of rubber fit just perfect. I couldn't have planned it better myself.http://nissaninfiniticlub.net/...t=500

Put it all back together. Now I have adjustment with the brass plug on how much seat pressure the spring will apply to the plunger. I thought that might come in handy in case the solenoid isn't that powerful.Anyway, put it back on, car ran just DANDY and now I can adjust the idle down to 600 (with tps unplugged). I actually had to idle it up a little, because I'm so used to it running so high!!!So my brother and I went out for a ride, and the car runs just PERFECT!!!! Idle goes right down when getting out of gear. Idles like a stone! Just completely fixed my problems!!!!

Sorry for the long post, I'm still so excited!!! Just had to share with you guys. Thanks again for the help!!!! I wish I could shake your hand and tell you how much I appreciate it!THANKS!

p.s. pulled the codes when I got back and still had the 34-knock sensor, but I'll save that for another topic and another day!

THIS FORUM RULES!