shadyonedeath

iTrader: (10)

My Throttle body throttle cable "half-moon" thing doesnt even touch the Stop screw used for adjusting the IACV idle.

My car idles high so im trying to plan everything out before i mess with it since the IACV is almost destroyed due to whoever worked on the car before my ownership.

KyleFort32

iTrader: (3)

while where on this topic is it okay to clean the throttle body with carb cleaner

shadyonedeath

iTrader: (10)

Yes.

shadyonedeath

iTrader: (10)

Yep, so what if I cant go any lower and my rpm is at like 900? Should I lower my IACV screw and THEN adjust from TB and back to IACV?

shadyonedeath

iTrader: (10)

Yup...so my IACV screw blew up when i tried to turn it. Literally. Blew into pieces. Harsh weather really takes a toll on these plastic screws..

Are they replaceable or do i need a new IACV unit?

96blkonblkse

iTrader: (18)

I had this problem..then i realized my TPS wasnt unplugged. Sounds stupid, but i made the mistake, im sure others probably have too.

If adjusting the screw all the way down doesnt do anything, you might have to play around with the TB. Have you had the TB off or been messing around with it?

modenaf1

iTrader: (3)

The factory service manuals say to NOT mess with the Throttle Body stop screw. Those are set from the factory and there is NO way to return it to factory stock settings.

All idle adjustments should be done on the IACV. What part of your IACV is messed up from the previous owner? It might be easier to go to a junkyard and get another IACV than risk messing with the stop screw on the TB.

shadyonedeath

iTrader: (10)

my IACV plastic screw blew up when i tried to turn it. It was really brittle.

njmaxseltd

iTrader: (19)

Here is the process for adjusting the default idle stop on the TB and the IACV.

1) Warm the engine up to operating temp, at least 15 minutes of operation so the coolant is hot.

Turn off engine

2) Unplug the TPS

Start the engine

3) Adjust the default throttle body set screw to obtain 500 - 550 RPM's with no accessories on. (no a/c, no heat, no lights, no ,radio, nothing!)

Turn off engine and reconnect the TPS

4) Start the engine and check idle speed, adjust the IACV to obtain 600 - 650 RPM's


I believe this information is in the Haynes shop manual. It's probably somewhere in the FSM as well. When the TPS is disconnected the IACV becomes inactive. That allows you to adjust the default idle at the TB.
You should not throw a check engine light during this process. Only start the car ONCE with the TPS disconnected, if it stalls while your doing this and you restart it, you'll set a CEL with the TPS code. Simply clear it when your done.

shadyonedeath

iTrader: (10)

I did this but my TB stop screw was backed up all the way and i was still at around 800-900 RPMs.


anyone know if the screw part of the IACV is replaceable?

MOHFpro90

iTrader: (11)

Do you need an IACV? I have one I am not using.

shadyonedeath

iTrader: (10)

****..wana trade? Just dropped 6k to buy this car, so im broke.

My IACV still works, idles fine. Its just the harsh weather wherever my car came from took a toll on the plastic and made it brittle.

njmaxseltd

iTrader: (19)

Is there enough slack in the throttle cable to allow the TB to close?
The only other thing that could be holding the TB open is the cold fast idle cam and plunger. Check to make sure that is operating correctly.

Get a new IACV or try to find a used on here on the org.

Have you checked for a vacuum leak? That could give you a high idle also.

shadyonedeath

iTrader: (10)

I didnt think about the TB cable, good call. But I think the butterfly plate is fully closes though. Ill double check. Thanks

shadyonedeath

iTrader: (10)

Still have this problem. When disconnecting the TPS and unscrewing the Throttle Body adjustment screw all the way, it still idles at +1000RPM. Even if I adjust the IACV all the way in or out, it makes minuscule adjustments; about 100rpm-+. I've been sourcing vacuum leaks for a while now because that's the only reason I can think of that would make it behave this way. I think it might be the IACV gasket or the Throttle body gaskets. ...if its not, I don't know WHAT it could be since I've just about sealed everything else.


Any ideas? Very high RPM when TPS disconnected, despite shutting TB plate completely closed.

jholley

iTrader: (13)

With the car warmed up and the TB plate closed measure the resistance of the first 2 pins of the brown TPS connector. It should read between 500 to 550 ohms. If it's reading a higher resistance then loosen the TPS mounting screws and easily turn it clockwise until you get a resistance within that range. After that follow the steps in post 9.

shadyonedeath

iTrader: (10)

It's not the TPS. I'm well aware of how to adjust the TPS using feeler gauges. Readings are normal.

njmaxseltd

iTrader: (19)

It seems like you have an intake leak somewhere. Are you sure the TB is closed and not hanging up on something? Did you check the cold idle circuit, specifically the plunger located down to the left of the TB? If the plunger is hanging up it will keep the TB open. I believe the plunger is normally out when the car is cold and goes in as it warms up, I may be mistaken and it could be the opposite. Watch it as the engine warms up to make sure it's moving and closing the TB as engine temp rises.

I wouldn't think it to be a vacuum leak as that would be a lot of unmetered air and should throw a check engine light for a lean condition. (air not seen by the MAF)
I think the issue is with the TB or IACV in some way as both of those draw air through the intake system and the MAF see's it.

shadyonedeath

iTrader: (10)

See, the thing is i'm using a 5th gen throttle body that did NOT come with that cold air plunger. I didn't use the 5th gen IACV or its coolant adapter under the TB so I have no cold start issues. What bugs me is no matter how far back the TB plate is pulled, it wont go below 1000rpm. (TPS disconnected). I would understand the plungers use under cold starts, but with TPS disconnected (both plugs), it idles way too high.

Also, the leak is frustrating me because the car seems to operate smoothly and quiet. Yes, there's engine noise and some hissing, but i cant seem to pin point it or determine if its just how the 00vi sounds due to its plastic composition. Im going to get new gaskets today so we'll see how that goes.

shadyonedeath

iTrader: (10)

How likely is it my Lower intake manifold isnt sealed? When I did the swap, I used new Lower Manifold gaskets and used the diagonal tightening sequence.

Cielo

never touch that plastic screw, adjust via iacv only.

shadyonedeath

iTrader: (10)

Woah, i just used a stethoscope and hear a lot of small hisses in my hoses, even the ones with clamps!

Is this normal? It's not loud but if I put it in the area of a hose/barb connection, you can hear a small sssssssss.


Can tiny vacuum leaks cause such a high idle problem?

njmaxseltd

iTrader: (19)

I think your hearing the whole intake system hissssss with the stethoscope. Pretty normal sound.

shadyonedeath

iTrader: (10)

Replaced every gasket from Upper intake manifold and up, replaced every hose, added clamps to every connection....i'm out of ideas. Still idles 1300 rpm with TPS disconnected (adjusted with feeler gauge).


I dont know if it could be my Lower intake manifold gaskets, even though they were knew when I put the 00vi....but im stumped.


Thanks for the help all.

maxed_out_99

i think if it was the lower intake gasket you would have a whole different set of problems

soo... if the throttle plates closed fully and the iacv is in proper working order, no vacuum leaks, TPS is adjusted and working, could it be that the cruise control cable is caught up somewhere? some how your getting too much air somewhere. if you can access a smoke machine thats the best way to find the leak. i doubt its on the lower half of the engine head gaskets, lower intake etc. cuz that would cause all kinds of drivability concerns missfires running rich hard start all that crap
it has to be a result of the 5th gen tb im guessing you have an adapter plate? if so maybe the sealing surface is warped cracked dirty something but i think thats where you should look if you have a leak there its going to mess with your idle
maybe the power rod is stuck open on the VI i dont know if that would change anything
just some thoughts

shadyonedeath

iTrader: (10)

Yea, with the TPS plugged in, it idles smoothly @ 780-800 rpm. I just feel that if its sucking in air to raise the idle to 1300rpm, something is NOT working correctly.

Unless of course my IACV works but it isnt closing? How could I test that? I know when I turn on the car, the IACV motor moves up and down a couple mm...stress on "a couple".

shadyonedeath

iTrader: (10)

Sealed her back up, nothing worked as expected. Idle now is 1700, despite sealing many of the apparent hose leaks with clamps.

Only thing I didn't mess with is the Lower intake manifold. Going to probably check that for swirl valve leaks.

shadyonedeath

iTrader: (10)

Vacuum leak test:

Plugged up the throttle body with a 2 1/2" PVC expandable plug and blew air (lungs) into my manifold through one of the hoses and to my surprise...the only air coming out of the manifold is through the IACV. The thick brass/gold 1/2" nipple that connects to the mid box is the only outlet letting air in/out when everything is sealed. Heck, I even sealed the unsealed IACV nipple with my finger and my engine held back pressure as I blew into it. This is good right? No leaks. It held it until I let my finger off the hose I was blowing into. Would blowing into the manifold also test EGR leaks? If it held pressure, that means everything is sealed correctly right?


So, can we rule that my IACV is dead? Is it suppose to close itself or be open during a IDLE relearn test? Because if its suppose to seal itself when I disconnect the Throttle Position Sensor, it's not happening and its probably dead.

maxed_out_99

the only time the iacv is working is when theres a load on the engine that would cause it to die like ac, power steering, sounds, (alternator) lights, all that crap or when the throttle plate slams shut other wise its "sleeping" replace it. you can probably find one fairly cheap either here or at a junk yard.

shadyonedeath

iTrader: (10)

I just dont understand why it's not sealing itself, I disassembled the large IACV sensor itself and everything seems to be in working order. It only travels about 2-3 millimeters because thats all the travel play its allowed.


Just to clarify, when people adjust their idle by disconnecting the TPS, is the IACV unit supposed to remain CLOSED or OPEN? As in, allowing air from mid-box to be sucked into intake.

maxed_out_99

it only activates under load remember it just a valve that controlled by the ecu or "switch"
here ill give you an example your car is idling with your wheels straight ahead under the hood you hear a whooshing sound from the filter that coming from the tb it never completely seals or you wouldnt idle you turn the wheel to the left your rpms drop for a split second then come right back to where they were thats the iacv coming on and working properly same goes for the a/c but the fan comes on as well once the drop is no longer smooth and returns quickly its time for a cleaning you probably have a hole somewhere

shadyonedeath

iTrader: (10)

First of all, Thank you very much for replying. Much appreciated to all those putting up with my problems, thank you.

Can I have a vacuum leak despite plugging the Throttle Body and blowing/sucking air into the manifold, and it holding pressure/vacuum? I disconnected the PCV and used that hose to blow into the manifold. Does that eliminate the Lower intake manifold and EGR possibility of a leak?

What about valve covers and spark plug grommets/seals, how could I test those for leaks if the valve covers are connected and have a breather in the front?

maxed_out_99

your welcome,
is your iacv a 5th gen or 4th with an adapter?
a leaking valve cover will not cause a high idle just a mess
the lower intake will have a different concern your engine will run like poo poo
the EGR would throw a code it has to be associated with the iacv

if you completely seal the tb the iacv should kick in or like i said the engine would die

shadyonedeath

iTrader: (10)

-4th gen IACV, Adapter plate, plenty of air flow.


NOTE: I've noticed that when I unplug my TPS (brown connector) for the idle relearn, my VAFC2 (under sensor check) shows a TPS voltage of 4.0v, like WOT. Is this normal? With the TPS plugged in, it's performs normal. Im guessing since its wired to the ECU and there is no resistance from the TPS being unplugged, the ECU is sending 100% throttle voltage to my VAFC? Hope that makes sense, and hopefully it hasnt been my TPS all along.

maxed_out_99

does the idle change when you unplug it

shadyonedeath

iTrader: (10)

Yea, thats the problem, it shoots to 1300+ rpm's with brown connector unplugged and IACV screw all the way in, and 1700rpm with IACV screw half way out.




Question, my 99 has a Diagnostic Test mode in the ECM adjustment screw. (the one we use to manually check codes). If turned fully clockwise, it points to "Diagnostic Test mode". Problem is, my 99 FSM doesn't even mention it...

is this used for anything? This VG30 and VE30 FSM talks about it under page 30 about adjusting idle/timing/fuel/etc.
http://www.nicoclub.com/FSM/maxima/1994/ec.pdf





and THIS is from my 99 FSM stating how the ECM leaves the IACV-ACC valve FULLY OPEN under fail safe mode...even though I dont have any check engine lights and it blinks 0505 from a manual trouble code inspection, meaning no codes.

maxed_out_99

i wouldnt even pay attention to that fsm dude i dont think its for obd2 and definetly not for our ecu

when you unplug the tps the rpms sky rocket? if the idle is maintained when its plugged in the tps is good all the signs point to the iacv spray some carb spray everywhere near it wile its running it should shoot all sorts of crazy high i have a feeling it has to do with the adapter plate. bolt up a 5th gen iacv with a new gasket and you should be good to go

it does make sense that the vafc would act as a tps though cuz its wired directly to the ecu

shadyonedeath

iTrader: (10)

I dont think 5th gen IACV's fit....when they changed from 95-98 style to 99, they also changed from 99 to 2000. It doesn't bolt on to our IACV housing. I remember I had to use the 5th gen IACV unit under the TB to use the 5th gen IACV, but even then, the 5th gen IACV i had wasn't cooperating with my car. (jumping idle from 1500 to 2000, constantly)



Would anything bad happen if I left the ECM screw on diagnostic mode and turned on the car?

shadyonedeath

iTrader: (10)

-ECU is NOT fried. Opened her up and everything looks normal. Every connection.

-What could possibly leak under the manifold near the valve cover? I hear a hissing sound back there but I can't source it or distinguish from the usual 00vi hiss.
-Also, to ask again...would the vacuum seal blown into the manifold also eliminate potential leaks such as the EGR or Lower intake manifold?

And to clear things up until this point:
-Vacuum leak test - Good. Holds vacuum and pressure with TB plugged. Only way air comes in and out is if I dont plug the IACV inlet.
-ECU - Good. Nothing fried.
-IACV = Measures resistance normal range - Undetermined.

maxed_out_99

i couldnt tell you anything about the vacuum lines on a VI i have a usdm manifold.
so the 99 iacv bolts to the VI?? I thought the VI had its own iacv? i think you should bolt the right iacv up it cant be that expensive and in my own opinion i feel its the right way to do it
the egr should throw a code p0400 and the lower manifold will cause all kinds of other problems "until it warms up then its fine" tell tale words that its a lower intake problem

99% of the time the ecu is NOT the problem