KA24DE high idle - IACV, AAC, Air Regulator???

Post by **90de4u** » Thu Nov 22, 2007 3:01 pm

OK, I just went through this long drawn out process to discover I had a vacuum leak. Fixed that, now the car wants to idle right around 1,800rpm. Once it warms up, same deal.

I used the idle adjust screw on the IACV...put it all the way in, nothing happened. Idle is still high. I read to pinch off the hose by the IACV that connects to the intake manifold. So I pinched that off with pliers and nothing happened. Same exact idle.

I have no vacuum leaks...I capped off all of the vacuum hoses under the throttle body. There were 6 of them. They were previously blocked with screws in the hoses, but I figured I'd clean it up a bit.

So would the IACV, AAC, or air regulator cause a high idle like this? I can't seem to get it to idle differently at all....pinch the hose, nothing happens. Idle adjust screw - nothing happens...

This is in a 1990 240SX with a KA24DE swap. Check engine light has been on as well.

Post by **90de4u** » Sat Nov 24, 2007 9:12 am

Bump.....anybody?

Post by **niemczykj** » Sun Nov 25, 2007 5:33 pm

i have the exact same situation... its like i wrote this story lol... but i have a 92 with a swapped, younger DE... and i dont have a CEL

im looking for an answer too, i have searched a lot and tried a lot under the hood...

im just about ready to rip out the whole intake manifold with all that stuff and clean it all up and hope that helps...

Post by **90de4u** » Mon Nov 26, 2007 7:05 am

This is ridiculous....I disconnected the vacuum hose that runs to the intake tube and the IACV / Air Regulator. I then unplugged the IACV harness. Turned the car on and and stuck my finger over the vacuum hose....there was suction. Pushed the throttle, there was still suction. Why is there suction when I unplugged the IACV??? There shouldn't be. From my understanding, it is only supposed to pull air in at idle. Well if it's disconnected, it shouldn't even do that.

Only thing I could think of, is it is stuck open...but even at that, it shouldn't do ANYTHING with it being unplugged. So I'm not sure what's up. I'm about to run to the junk yard and pull an IACV and slap it into my car and see if it does anything....doubt it.

Post by **krazydriver** » Mon Nov 26, 2007 8:45 am

think about what you said for a second.It's pulling vacuum CONSTANTLY. disconnecting the harness would only show that the ecu is not controlling the opening of the IACV. The valves can and do get physically gummed up where they are either stuck open or closed constantly.

if you just dump some seafoam/carb cleaner stuff down the hose from the intake tube into the IACV it will probably clean the valve out. If it still doesn't work, either remove it from the intake manifold and clean it thoroughly, or get one from the junkyard.

the iacv is a frustrating issue, but it's really not to hard to clean it.

Post by **90de4u** » Mon Nov 26, 2007 10:43 am

True....I am thinking it is stuck open...hopefully that is the problem. I just spent an hour and a half pulling an IACV off at the junk yard. There is so much crap jumbled up behind there....nothing really in the way since I have a swap. We'll see how it goes. There is a lot of dirty/watery carbon build up on the new IACV, which will get a good cleaning in a minute.

Post by **niemczykj** » Thu Nov 29, 2007 8:56 am

what was your result? did cleanin the IACV work?

Post by **90de4u** » Thu Nov 29, 2007 7:51 pm

Nope. I went to the junk yard, pulled off an IACV from what they said was a 92. Supposedly whoever did the engine swap on my car (previous owner) took my engine from a 95. This is a 1990, originally SOHC.So anyways, I pull off my IACV and run into a problem. The connectors on both IACV's are different. On my original one, they are small squares and easily go into the harness connectors. On the NEW one, they are rounded off and I could not get them into the harness because the connectors are too big.

I shaved off the "pegs" on the outside and managed it to plug into the blue harness. The yellow one was a problem though. I had to break off some of the plastic casing on the harness and insert the two wires from the IACV into the yellow plug. I was wondering if anyone else has experienced fitment issues or what??

Post by **slyspiff** » Sat Mar 01, 2008 9:42 pm

....fixed it was my ignition timing...now i screwd up the idle screw and i gotta fix my idle lol..
Modified by slyspiff at 10:51 PM 3/3/2008

Post by **Sileighty's Man** » Thu Mar 20, 2008 5:58 pm

What's up, I'm a Nissan technician and have been doing it for over 5 years. I'm a whiz when it comes to electrical but this is really turning my ratchet!!!

Alright, I have the same thing a '90 240SX RPS13 with a KA24DE swap. Now my problem is the idle is going from 1,800 to 2,000!!! I've been having this problem for a year now and NOBODY!!! Can find out what it is. I've been told that the wires under the intake plenum are crossed or something like that. I checked it out and according to the wiring diagram on the 90 240SX and the 92 240SX and they're just about the same minus the connectors on the IACV (square/round). So anyway, I have a new IACV AAC, changed the connectors from square to round, new battery, new alternator, new plugs, wires, oil change w/OEM filter and the notorious timing chain rattle. Oh and I found that the engine had SR20DET side fed injectors but that's not causing the high idle...I have the IACV adj. screw all the way in and there's no hose leak because I've replaced them with OEM hoses. So if anyone has the SAME EXACT PROBLEM and fixed it...PLEEEAAAASE, help me out. I have to smog the damn thing and it's been a year because I can't figure what the hell's going on...neither can the techs at NISSAN! We all don't know it all but I guarentee that some of us know something we all don't know and vise versa! Thanks peeps!

Post by **s13rb25det** » Sat Mar 22, 2008 4:45 pm

mine does the same thing and I think I my have fixed it. what i did was adjust the screw that is next to the idle adjustment screw it is covered in epoxy on some engines. I just messed with it a little and adjusted my idle speed and ign, timing. it seems to be working so far, I do have one question though. I crimped off my vaccum hose leading to my iacv from the manifold and it stalled my engine out. is this normal or not?

Post by **Sileighty's Man** » Sun Mar 23, 2008 11:27 am

yeah, it's normal but if it just stays on then I think it's bad. I'll have to look into that. I just replaced my IACV and it's factory brand new. I'm still having the high idle (1800-2100rpm) and it's driving me crazy! My timing n' everything was off as well. Whoever had the car before me is just a total idot or his mechanic didn't know what the hell to do. Anyway, I fixed the timing but disonnecting the sub harness to the emissions components and the idle was normal. The idle was @750rpm which is normal. Now after I did that I plug the sub harness back and BAM back to the same problem. I even checked the TPS (Throttle Position Sensor) and measured the resistance (Ohms) while it was closed and it measure about 10 Ohms. It's supposed to read @2 Ohms. So I think that the high resistance is telling the computer to open the IACV AAC and allow more air into the manifold! I have't been able to score a new TPS but when I do I'll be sure to post and update! I hope this helps me out because I keep hearing a differnt solution everytime and everytime these solutions do not work.

About the IACV having an extra screw...I know about the epoxy on there but I wasn't sure if that was a screw or not. In my opinion if it's brand new and that's the way you bought it my advice is not to mess with it but if it's working for you then so be it! But my concern is that the IACV/FICD(Idle Air Control Valve/Fast Idle Control Device) is brand new and it IS working but my Sub harness might be messed up or maybe it's my TPS that's causing the high idle. My master Tech says it's a possibility and it makes sense but it's a really rare to pin-point however. Well, if you or anyone can confirm this then let me know before I buy another expensice part and end up not being the problem...again!

Post by **Sileighty's Man** » Sun Mar 23, 2008 1:43 pm

OK, I got it! I disonnected my sub harness for the emissions and the idle went down to normal and I got a CEL. Then I unplugged the TPS and got a lower idle. I say the idle went down about 100rpm. After that I then plugged the emission's sub-harness and vioala!, the idle sustaned! I plugged the TPS back in and there went the idle up to 2000rpm's! So there you have it! it was the TPS and @ hard shut position it rated at 10+ ohms. the normal reading is supposed to be @ 2 ohms. The more the throttle is open the more the resistance goes up, sending a signal to the ECM saying, "you need more gas!" The TPS, I understand, is not an engine control component. It just simply says to the computer that you either need gas upon take off or cut off your fuel when you come to a stop! I guess that's why I don't get a CEL. Anyway, I hope this helps any of you who need help with the high idle thing but then again not all of our cars are the same and we may have the same problem...there are many problems that can lead to the high idle. I'll keep you posted if it is the TPS or not for sure...I still haven't replaced it yet but I'm pretty sure the this is the problem I'm or you are having.

Post by **s13rb25det** » Sun Mar 23, 2008 5:32 pm

thanks for the info it is really informative please keep us updated.

Post by **twowheeletex** » Tue Mar 25, 2008 5:53 am

s13rb25det wrote:thanks for the info it is really informative please keep us updated.

defiantely. I agree. I have been in the shadows and havn't needed to really ask any questions or post because of quality work y people like you. keep it up, it's awesome. I do have one thing, changing your fuel pressure regulator will not help this problem either. it may seem like a useless addition, but i did and my problem mirrors this exactly.

Post by **slyspiff** » Tue Mar 25, 2008 1:57 pm

i agree also with this guy..unplugging the TPS did the same to my car...i had idles of 1800...cuz i went all around and researching the differnt idle valves nissan use for the 240... some uses a plastic screw...other idle valves have a metal screw with smaller width...some have a spring loaded valve and other ones a square block wth a hole...soooooo....i notice it wasnt my idle valve...cuz i unplugged the TPS and my idle went down to 750..so my guess is either the TPS that is sending a signal for more gas...or a signal to pass more air in by using the IACV valve? iono...my guess is either the TPS is out of calibration or the sub harness has a corrotion somewhere causing it to shoot up in ohms? <<<hardly poossible?...hope this helps latez.. reply on this i wuld like to know if im right at least lol..ima go check out my TPS...how u check it? anyone knows?

1992 Nissan 240sx s13.5?....has an s14 engine(1996)..with s13 intake collecter but s14 lower intake/s13 exhaust..wit EGR pipe s13(s14 different)..and its old OBDI system. shooting for a KA24DE-T

Post by **twowheeletex** » Tue Mar 25, 2008 3:48 pm

you Ω out the TPS. the FSM says it should be ≈ 2 Ω when at closed throttle position and ≈ 10 Ω when at WOT position. if you are lookingat the tps connector with the clip on top, the pins are numbered from left to right, 1,2,3. probe the 1&2 pins and it your reading is within limits then your TPS is good. if you probe the 2&3 position with your key in the on position engine not running you should get .5 v ± .2 v. this lets you know your TPS is adjusted right. if you have the same problem I it have lets you know you must look elsewhere. I checked the Ω of my IACV - air regulator which should be ≈ 75Ω, and only came up with 60Ω. so I am going to clean it out this weekend and see if I can't get a better reading. if not, I'll replace it.

couple other readings to help out anyone without a FSM.

Engine coolant temp sensor68 °F = 2.1 - 2.9 Ω122°F = .68 - 1.00 Ω176°F = .30 - .33 Ω

Iacv-Acc10 Ω

Post by **Sileighty's Man** » Tue Mar 25, 2008 6:07 pm

OK, I've had my nose in the Factory Service Manual for the past 2 hours looking this subject up amongs other things! Anyway, My theory along with those who posted after me seem to be correct! I just ordered the TPS for my '93 motor and when it comes in I'll install it and give it the right adjust ment (don't for get to turn it with the key in the ON position) set at 5V or around there (It could be .5v, I just forgot!).

I also spoke with some of my 240/Silvia buddies about this issue and all but one didn't have a clue. The one, however, belives that the TPS is causing the high idle because durring a test drive we noticed the car would come down to normal idle (750rpm +/- 100rpm) durring decelaration with no load on the engine (brake only with stick in N) and when at a complete stop the engine shoots back up to 2000rpm. I also noticed the smell of gasoline sometimes when I'm either driving or at idle waiting for my car to warm up in the morning but it's really faint! It happends on hot days mostly given the temperature when gas is hot it vaporizes more or something like that, I'm not a chemist but I do know cold heat properties. Like I said, I'll keep you posted and I have this thread on RSS (via Win Vista) and I always try to be as up to date as possible in real-time! Good luck tuners!

-R.G.

Post by **s13rb25det** » Sat Mar 29, 2008 4:11 pm

any updates? I just ordered a iacv unit I am so sick of screwing with it so I just forked out the cash.

Post by **Sileighty's Man** » Tue Apr 01, 2008 2:45 pm

OK, I installed a brand new TPS and guess what? It was the problem! My idle now is no problemo! I do, however, have a EGR code though and there are times when I have to actually lift the accelerator pedal toward me with my foot at times so I guess I have to adjust my throttle cable and see what's up with my EGR. I do have a CEL by the way! But other than that everything else is fine. Aside the little things the car is running great now and my gas mileage is better now as well. So before dishing out $140+ for an IACV look into a TPS and look at your wiring too! Well if you have any questions hit me up I might be able to help you out with whatever you got! Peace!

Post by **s13rb25det** » Tue Apr 01, 2008 2:56 pm

yeah, my TPs is pretty new and it tested o.k. I am haveing a hard time finding a IACV for my year 240 though. they all are for the 95 and up s14s with different plug ins.

Post by **Nastjuid** » Wed Apr 02, 2008 10:14 am

^ try calling your local nissan dealership and get a part number for the IACV, then check courtesyparts.com They're OEM nissan parts for less than dealership prices.

@sileighty

Hey thanks for going through the motions. You said in a previous post, "there you have it! it was the TPS and @ hard shut position it rated at 10+ ohms"

Can you check that again with your multimeter for us and confirm that the TPS now shows ~2ohms at hard shut? My TPS is also reading 10ohm at hard shut, but I need to do injectors, rings and bushings to fix an air leak to get a solid idle.

Post by **Sileighty's Man** » Tue Apr 08, 2008 10:39 am

OK I actually changed the TPS and my idle is OK now. I'm still getting a little surge to 1.5rpms when I'm coming to a stop or when I give it a little blip of gas. I comes back down but it hesatates on the way down. I checked the hard shut position of the TPS with the new one installed and it read about 2.2ohms. Not bad if you aske me. And when I open the throttle it reads out between 2-10 ohms. So according to the FSM that would be considered normal. I had to asjust my throttle cable now because it's sticking a little after I lay off of the gas, i.e. Exiting the freeway. But with the current cable setting it brings down my idle a little bit faster...but not like it should. It still hesetates. I do have a CEL and chekced it and I think it was an EGR code. I have to look into that again as well. Anyway though, my idle is normal and now it's a drivability issue and CEL. I'll keep you guys posted. Peace!

Post by **Nastjuid** » Tue Apr 08, 2008 10:53 am

Thanks again for checking that. The reason I asked was because somewhere in the giant pile of idle issue posts on multiple forums, someone said that the FSM is wrong about which pins to measure resistance across. Of course, I trust the FSM more than random person X on a forum, but when I ohmed mine out, I read 10 at hard shut across the pins that the FSM said, and 2ohm hard shut across the two the other guy said, so it planted that seed of doubt in my mind.

So it was ~2ohm hard shut across pins 1&2 looking at the pins with the tab pointed up. Time for a new TPS for me then

Post by **twowheeletex** » Tue Apr 22, 2008 11:05 pm

I adjusted my idle screw in all the way on the IACV, picked off the epoxy on the brass plug, and screwed that in all they way (another thread said the spring in there could get weak over time and cause the idle to rise so I tried it) checked my codes, got a knock sensor code, changed that, checked my vacuum hoses, cleaned my maf, removed my emissions, capped off all non essential vacuum components, and still the idle sits at a frustratingly unwavering 2000rpm, warm or cold. I went through and checked all the readings I could possibly get from my tps, here's what I got:

w/clip on top (1 2 3)closed ← 9.6Ω → measured from pin 1&3closed 8.9Ω 1.2Ω measured between pins 1&2, & 2&3

opened ← 9.6Ω → measured from pin 1&3opened 1.6Ω 8.6Ω measured between pins 1&2, & 2&3

my question, is my tps bad judging by these readings.

Post by **Driftnoob** » Thu Apr 24, 2008 9:10 am

same here, tryin to find the answer !!!!

Post by **twowheeletex** » Sun Apr 27, 2008 8:28 am

bump. . . anyone?

Post by **WhiteKnight** » Wed Jun 04, 2008 1:46 am

The FICD solenoid could do this if you have A.C. The manual says to measure the voltage on the FICD connector.

Post by **mick** » Sun Apr 05, 2009 6:09 pm

What is a CEL?

Post by **vancouverbc** » Sun Apr 05, 2009 7:10 pm

check engine light

KA24DE high idle - IACV, AAC, Air Regulator???

KA24DE high idle - IACV, AAC, Air Regulator???

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (90de4u)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (90de4u)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (niemczykj)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (90de4u)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (krazydriver)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (90de4u)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (niemczykj)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (90de4u)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (slyspiff)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (Sileighty's Man)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (s13rb25det)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (Sileighty's Man)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (Sileighty's Man)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (s13rb25det)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (Sileighty's Man)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (slyspiff)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (twowheeletex)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (Sileighty's Man)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (s13rb25det)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (Sileighty's Man)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (s13rb25det)

Re: KA24DE high idle - IACV, AAC, Air Regulator??? (Nastjuid)

Re: (Nastjuid)

Re: (twowheeletex)

Re: (mick)

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