Cleaned AAC iac iacv and created a new problem

[sheadee240]

1994 Infiniti Q45t tcsI was trying to clean this as maintainence, but afterwards car idles at 1200 instead of 650. unplugged the AAC and idle dropped, but after cleaning no change when unplugging. I ohmed it out at 9.2 spec approx 10 ohms. Everything seemed to move freely, when I cleaned it, but now it is acting as if stuck in the wide open position. checked for vacuum leaks found none, I'm planning on removing again to bench test with 12 volts...Any input??
Modified by sheadee240 at 8:02 AM 8/4/2006

[CrimsonQ]

Replaced with a new gasket?

[squeefoo]

Did you gently screw the adjuster all the way down and back it out ~2.5 turns?Miss a hose?Clean the connector contacts?Squeeze the 3/8" hose going up to #5 upper runner and see if the idle changes?

<shrug> LMK...

[maxnix]

The cylinder that is the valve itself is threaded, and I believe I left mine in the fully extended position. I'll remember later and post back.

Must use new gaskets on IAC and EGR valve and throttle body.

[sheadee240]

Did you gently screw the adjuster all the way down and back it out ~2.5 turns?Miss a hose?Clean the connector contacts?Squeeze the 3/8" hose going up to #5 upper runner and see if the idle changes?

<shrug> LMK...

I used a brand new infinity gasketI did gently bottom the adjuster and back it out 2.5 turns ( which is exactly where it started), At first I didn't mess with the adjuster, and then after high idle I set it and that wasn't the problem.I didn't miss a hose there was just the one large hose at the bottom which I checked and looked good.I did not squeeze the hose, although that should have been my logical nest step as my suspicion is that the aac is internally stuck open.I will try that first thing this morning.Thanks

Anyone else know anything about the piston that is the valve being threaded? I did spin the piston around so that I could clean the gunk on the other side of it, but it never occured to me that it could be threaded???

Only other thing that I can think of is that a piece of old gasket was unlucky enough to fall into the hose (I should have plugged it earlier) while I was scraping that bastard old gasket off. And was then unlucky enough to jam the valve into the open position. Maybe less likely than me somehow misadjusting the threaded valve that is the piston if that is the case.

I didn't clean the connector, but I don't believe that to be the problem as I disconnected the conn with engine running before disrupting anything and car almost stalled, now afterwards disconnecting the plug doesn't change anything.If squeezing the hose confirms my suspicion that the aac is mechanically stuck open, I think I will pull it and bench test it with 12 volts and see if the piston slides easily and goes back to its home with no voltage??

[Q45tech]

Remember even in summer you have the other circuit [the coolant temperature warm up idle cam] on throttle body. NEVER NEVER touch these as impossible to reset correctly once they have been turned from oem calibration.

You must make sure the engine is warm HAS BEEN RUNNING FOR 10 MINUTES before setting the idle rpm via the IAC air bypass screw.

You cannot trust tachometer when setting idle speed jard to resolve 25 rpm at 675.

[sheadee240]

Remember even in summer you have the other circuit [the coolant temperature warm up idle cam] on throttle body. NEVER NEVER touch these as impossible to reset correctly once they have been turned from oem calibration.

You must make sure the engine is warm HAS BEEN RUNNING FOR 10 MINUTES before setting the idle rpm via the IAC air bypass screw.

You cannot trust tachometer when setting idle speed jard to resolve 25 rpm at 675.

I didn't mess with the throttle body at allEngine was warm when I set iac bypass screw.I do have a plms interface that I can use when the time comes, but I am so far away from 675 rpms right now that I really don't need the laptop readout of rpms untill I can atleast get in the ballpark.

I did other services at the same time fuel filter, pcv valve, and cleaned battery terminals, but I don't think any of these are likely related, sounds like all IACV to me?????

[maxnix]

Might be different IAC valve on the VH45DE. My comment referred to VH41DE. Sorry for misreading.

[sheadee240]

OK I squeezed the hose that supplys air to the AAC (IAC) and The idle dropped considerably. It sounded lower than a normal idle with the IAC supply squeezed shut. So I guess it'll have to come back off again to see whats going on inside there.

[maxnix]

Or be certain you closed the threaded adjustment screw rather than start from a totally open position.

[sheadee240]

Yes, I'm pretty sure...Clockwise untill lightly seated, and then backed out 2.5 turns, but initially I didn't even mess with it at all and I still had the problem.

???
Modified by sheadee240 at 8:07 AM 8/4/2006

[maxnix]

Sounds like you got it right.

[Q45tech]

Consult helps so much because it reports the PECENTAGE of time the solenoid is open adding extra air around the fixed [time] bypass valve port [what one adjusts]................much like an injector duty cycle.

What you are looking for is 10% duty cycle with bypass 2.5 turns open in Park............going to drive yields 15-25%, turning ac on yield 30-35%, turning steering wheels adds 5%, turning headlights on 2-3%

At 60 mph AC on you will have 60% duty cycle so that when you lift your foot off throttle the ECU can create an orderly coast down rpm/speed without chancing that the engine will die.

When you do a Consult power balance it will go to 80% to raise the idle rpm up to 1200-1500.

Specific Consult test to check IAC Zero%, 10%, 20%, and 80%

Rpms should be lower with IAC disconnected or forced to ZERO vs the nominal 10-15% idle.

Getting this spot on is necessary for that as new performance feeling.

About 95% of Q I check are out of my spec......not clean, Throttle not clean, pcv restricted [dirty], or just misadjusted bypass screw.

[sheadee240]

I could probably disconnect for 0% duty cycle and supply a constant 12volts for 100% duty cycle, if I just wanted to verify that the valve itself is internally stuck open. I'm guessing that the solenoid itself does not have any type of position sensor inside (Only 2 wires) , so I could therefore accomplish similar results by checking duty cycle with a good DVOM (fluke 88) under different conditions. This would rule out the ECU as a possible cause if passed all test, which I'm not really suspecting the ECU or wiring at this point based on 1200 rpm with 0% duty cycle.

I'm definately going to pull it and bench test it today, If it still acts up after inspecting everything I am going to drop the $300 (OUCH) unless anyone has a good used IACV AAC IAC to sell me cheap??

THANKS AGAIN!

[Q45tech]

I though you said you spent the hour with tiny tools [dental pics, etc microscope cleanroom] and multiple solvents cleaning ALREADY...............you will see the cylinder [valve] on the tip of solenoid arm and the close tolerances involved to get a fine resolution of air flow.

A work of art when it is clean and tuned precisely..................K&N sends oily dirt to IAC................I made that mistake 12 years ago.

Clean or replace the PCV valve and the output hose [and internal brush if so equipt].

If everything is not like brand new [spotlessly clean] the system cannot work like brand new!

You can watch duty cycle creep up and up and up as the miles since cleaning increase......................way to complicated a system for the typical car owner or typical technican of that era to TOTALLY comprehend.

[sheadee240]

I though you said you spent the hour with tiny tools [dental pics, etc microscope cleanroom] and multiple solvents cleaning ALREADY...............you will see the cylinder [valve] on the tip of solenoid arm and the close tolerances involved to get a fine resolution of air flow.

A work of art when it is clean and tuned precisely..................K&N sends oily dirt to IAC................I made that mistake 12 years ago.

Clean or replace the PCV valve and the output hose [and internal brush if so equipt].

If everything is not like brand new [spotlessly clean] the system cannot work like brand new!

You can watch duty cycle creep up and up and up as the miles since cleaning increase......................way to complicated a system for the typical car owner or typical technican of that era to TOTALLY comprehend.

My intention was not to clean again, but rather to inspect and then bench test with 12 volts to check for sticking of valve.I thought that sounded logical, but now I'm not so sure.Amyways, I also just replaced my transmission revolution sensor...While driving around this morning with no transmission malfunction message for the third day in a row (SWEEEEET it's fixed) I was really ripping hard and enjoying flawless shifts. To my pleasant surprise, when I park car rpms a tick above 600 (I will set with PLMS interface-laptop to ensure accurate rpms @ idle warm)I believe some of the old gasket fell into the AAC hose and got stuck in those close tolerances in the AAC. I noticed my oversight while scraping the old gasket off, but by the time I covered the hose it may well have been too late. If it does no reoccur I will stick with that conclusion, if not I may still bench test to check for nice stick free smooth operation, unless thats a stupid idea??My pcv valve is brand new as is my stock nissan air filter and my throttle body is clean, although I do need to clean all of the passages in the TB not sure of the condition. While I'm sure that is critical maintenance, I don't think it is related to my 1200 rpm idle that I was having as it idles perfectly until I disrupted the AAC. That is next on my list along with transmission fluid service tc rod bushings front upper links and then maybe a custom z32 diff.

THANKS AGAIN!

[sheadee240]

Played with plms interface and software tonightIt has a set base idle feature which disables the AAC through the laptop (not sure if it does anything else)My idle and base idle were both already 650 dropping to 600 in drive. There was 8% AAC duty cycle @ no loads and 35% duty cycle with AC and high beams on. Car idles for 25 minutes without exceeding 178 degrees and the tps was reading 0.46 V registering throttle off to ECU. Requesting 100% duty cycle with laptop software yields 1350 rpm as diplayed on laptop. Cylinder balance test shows no difference between any one cylinder cutout relative to others in rpm. Car is running really nice. Front upper links are now most annoying problem. Hopefully those will be replaced by Thurs.

Thanks Again!

[Q45tech]

Remember the idle is the SUM of the IAC bypass, IAC solenoid duty cycle, and air thru the TB [under and around the throttle plate] plus any gasket leaks [plenum runners injector gaskets] and into plenum hoses.