cdoublejj

IAC and ECM usually you replace both, only use OEM IAC replacement. the usual stuff.


Idle WAS so high, it was banging in to gear, BAM!!!


Well I unhooked the battery for a 2 months and the idle dropped to 1400, it's drivable again.


I'm not so certain it's the IAC and ECM because if it's the ECM along with the IAC it should run like absolute trash, if I'm not mistaken Yet it's drivable and runs/drive like it should except for the idle also the trans is shifting a little funny my dad says but, other wise normal.


(dad says trans seems like it's shifting harder, but again it feels like it's driving normal, so it's not a HARD shift) {I only mention that incase it's related is all}


What's really weird is when we pull of thee oil cap it the idle lowers. Put the oil cap back on or seal the hole with your palm and it raises right back up.




EDIT: the Snap-On Verus is showing the IAC stepping down (trying to close/idle down)

cdoublejj

It would seem the TCM and ECM are separate.

cornholio

iTrader: (1)

Wut...

You don't have to replace ecm with iac, only if ecm gets fried

1400 is high idle regardless... what were you idling at before?

Tell dad to try idle relearn procedure

cdoublejj

we tried re learn and idle return, no go. can't find any vacuum or intake leaks either.

IAC is stepping down, trying to correct idle speed. shot some propane in air intake while we were checking for leaks and the computer compensated (idle up then down) .

It should be noted when that when you take the oil cap off and the idle drops back down a few hundred RPM it only lasts for several seconds.

We starting to the ECM is faulty but, not fried. As some who works on electronics and computers I have seen such things before. Working but, not stable/correct.

weird stuff man. O2's look good/correct on the scanner. In fact there were 3 of us, my dad and godfather. ANYWAYS, godfather ran the Verus (scanner) and checked out all the readings and all 3 of us look for leaks or visual indicators in the engine bay, even put it on the lift and looked underneath.

This is some really trippy stuff, the car looks and sounds to be running correctly and sounds good too! All except for the high idle and hard-ish shifts, we got a HARD shift last night from 0-40mph semi hard acceleration.

EDIT: we forgot what it was idleing at before, i let it sit fora month with the battery on hook, but, it was going 40mph idleing and BANGing in to gear from park, so it came WAAYY down after letting it sit for a month.

EDIT: We tried adjusting the jam nut/idle screw and that didn't help either.

colt149

iTrader: (1)

You need to hook up your vehicle to OBD II scan tool with live feed to detect error code and impending error code. I believe your problem might be the throttle assembly or MAF sensor. You can only reset the ECU thru Consult II of Nissan Stealership or do it yourself by throttle relearn procedure.

cdoublejj

Been there done that, that's exactly what the snap-on Verus is and then some. I could maybe see it being the TPS. I could also understand if there is very very very specific set of values we should be seeing on the TPS/throttle body/sensors that we should be seeing but, don't know about.

It's not his first live feed/scan though, he has done quite a few before and on THAT merit all things look good.

ON THAT TOPIC, i need some words of wisdom on replacement TPS units. I know the IAC HAS to be OEM Nissan just like o2 sensors on most vehicles, is the same true for the TPS?

colt149

iTrader: (1)

For VQ30DE , you can replace the TPS separately
For VQ35DE engine, you need a new throttle assembly, Nissan dealership only sell remanufactured throttle assembly (reman) for 5th Gen Maxima. Better off buying the NWP engineering 75 mm wide bore throttle assembly (brand new hitachi). If happen you need to replace the throttle assembly , you need the OBD Consult II of nissan stealership for the ECU to recognized the reinstalled new throttle assembly. Or do it yourself by performing the throttle relearn procedure. My mechanic has a high grade OBD II Snap On Brand scanner, he paid the company $600 every 6 months to upgrade the software. The said OBD snap on scanner failed to do the relearn of my new throttle assembly. I have a close friend that work in that dealership, hook up my engine to the Consult II and reset my ECU and the engine run smoothly with the new throttle assembly.

cdoublejj

how do i know i'm not buying the wrong TPS?

cdoublejj

It looks like I want to get the Hitachi TPS.

00Lightsout

check the PCV yet??

cdoublejj

Just picked up a PCV and ECM. Next purchase will be a TPS. I think we will re try the re learn but, with a stop watch this time. (all assuming the Verus can't just initiate directly)

Then we will see what is causing the exhaust leak that showed up the other day.

cdoublejj

okay so if unhook the hose (the hose that goes to the PCV) from the metal tube on top of manifold it idles down fora few seconds just like taking off the oil cap did. hell it will evne start at 650 rpm. then it goes back up again. there must be some sort of clog some where.

replaced the PCV valve AND hose no difference at all, hose was rock soldi and broke during removal and the PCV was gummy but let air pass through and rattled HOWEVER the OLD pcv valve lets air go through both ways, the correct way flows freely the wrong way is restricted. thew NEW pcv valve only lets air go the through the 1 correct way.

whats funny is i track that metal tube to here...





the clip/ring is NOT missing i removed it before the photo thinking it was another valve which it may be but, if it is part of the plastic intake i don't want to snap it off.

cdoublejj

ACTUALLY it's doing funky stuff WITHOUT the hose and PCV valve. it will idle at 650 rpm then go up to 1k to 1.1K then dip back to down to 650 rpm and repeat. it has rough lopey idle at 650 rpm.

EDIT:

https://www.youtube.com/watch?v=vFzFs57cDBg&feature=youtu.be

https://www.youtube.com/watch?v=SpC9dnHo3mw&feature=youtu.be

WTF?

Hmmm.......the PCV is actually a metered air leak. I am unfamiliar with the VQ system, but on LSx platforms a bad PCV system wreaks havoc on idle. I would make sure that there are NO leaks, which I am sure you have. I think you are on the right path tracking a pcv Vacuum leak. I have an 01 in the shop now, I will go outside and look at anything I think might help you troubleshoot.

cdoublejj

https://www.youtube.com/watch?v=vFzFs57cDBg&feature=youtu.be

https://www.youtube.com/watch?v=SpC9dnHo3mw&feature=youtu.be

cdoublejj

if it was leak, it should in theory make NO difference. how when i remove the hose (creating a leak) it idles down.. sort of what the videos to see for your self.

EDIT: at least in theory. i have a different used ECU on hand that is supposed to be good and was supposedly tested. i hear you have to reprogram the keys, idk it will start or not if swap in that ECU.

EDIT: maybe it's something like this,

http://troubleshootmyvehicle.com/nis...lenoid-tests-1


EDIT:

https://www.youtube.com/watch?v=vFzFs57cDBg&feature=youtu.be

https://www.youtube.com/watch?v=SpC9dnHo3mw&feature=youtu.be

WTF?

Maybe....it definitely should make a difference as it is metered air from behind the mass air being sucked......at least on what I've tuned. No, if it's unmetered air from in front of the MAF then in theory is shouldn't make a difference. I don't know. I looked at the one out in my shop, but I put a supercharger on it, and so all the factory vac lines are caddywhompus right now.

cdoublejj

because of the positive pressure or because of the age? interested to hear how that supercharger works out!

cdoublejj

Hooked the verus up AGAIN
Scanned it AGAIN
watched the readings AGAIN
played with the timing AGAIN
checked the hoses AGAIN
checked for leaks with propane AGAIN
played with plenum AGAIN
Sent ECU off for examination and repair.

probably would be best to replace the IAC and Throttle position sensors with OEM replacements.

nestorlugo

iTrader: (11)

Those two cost a fortune and without a real answer you'll waste a ton of money,try to hunt down a good used tb and swap it out,reinstall and give it a shot

nestorlugo

iTrader: (11)

[QUOTE="nestorlugo;8996092"]

Those two cost a fortune and without a real answer you'll waste a ton of money,try to hunt down a good used tb and swap it out,reinstall and give it a shot

Which ecm did you sent out for repair? Original or the one you purchased?

cdoublejj

yet another high idel....

New optima battery (yellow)
new hitachi IAC
new Hitachi TPS
ECU repair by David Ruberg (sells service on ebay)

idles normaly!

as for the cause of the issue


the throttle body was a MESS! black gunk every where. once i remove the entire IAC, corrosion all along the entire gasket, the holes for the air flow were fine except one was black, but, the corrosion was the entirety of the IAC gasket.

the repairs consisted of the above AND, attention to detail on the TB, where IAC mounts was carefully filed down with a metal file, it was actually not flat, it had pretty bad high spots where the screws go and along a few corners in the "gasket channel", it was levled out carefully and skillfully with the file. the corroded gasket channel was clean with a scribe (gently). the new IAC gasket was paired with a thing light coat of black silicone.


no adjustments on the TPS or idle set screw yet. i think when my dad tried adjusting the idel set screw he was careful to watch how many turns and set it back stock.

i probably when on a 45= minute test drive, shut it off a few times and turned accessories on off and it stat just above 500 rpm in the 650-750 rpm range.

it seems so far everything is good.