ppetruccelli

Yesterday I changed my idle air control valve. Quite the job. It is time consuming, but pretty easy. My reason for changing it was because my car wouldn't idle without stallling, and the car's computer put out the code PO505, which calls for an idle air control valve problem. So, I went to Nissan (the only supplier of the part) and bought a new one for $404 Canadian (taxes included).

To start things off, it is located under the throttlebody and very difficult to get to. So, I removed the whole thing. Plus, you get the chance to clean it out well.

Step#1 - remove air box and all pipng leading to throttlebody. You will have to undo one electric connection. You can simply turn to air flow meter upwards and let it sit on the intake manifold without completely removing it.

Step#2 - remove the two coolant lines leading the the idle air control valve, and the two brackets that support other lines that are in the way.

Step#3 - remove the 4 bolts from the throttlebody, and the two electrical connections, and pull it off.

Step #4 - Undo the two throttle cables by pulling them up and sliding them out of the track (should be easily done).

Step #5 - Remove throttlebody.

Step #6 - Replace the idle air control valve (5 screws must be removed), and clean up the throttle body. I had a really hard time getting the screws out for the idle air control valve, so make sure you lube them up before trying to get them out because the screws strip easily.

Step #7 - Reverse order, and replace everything.

Note: No additional parts are needed. No gaskets have to be replaced. The new valve comes with new screws and a new O-ring type gasket.


Hope this helps some one!

ronrule

If you are just trying to clean the IAC Valve, is it necessary to take everything else off as well? Thanks!

A33FORME

Ghost_54

iTrader: (13)

There are a number of threads here on the .org that describe this happening but so can a shorted out electric motor mount, it can also short out the ecu

Tyrone

yes this is happening to me right now car is the shop because of a bad IAC... trust me dont wait change that IAC aspa. cleaning the iac is a no no just get a new one fron the stealer $350only..

A33FORME

Just for information, How many miles on your car, wondering if mine has been done yet and how much will a new computer cost?

L_U_D_I_AMaxima

iTrader: (3)

yep I did that mistake, cleaned mine. then about 500miles away from home I had to pick up the in-lwas from O'Hare airport, just as I was getting off the highway on the exit ramp my SES came on and the car started acting funny rpms up and down like crazy... I knew that this was the symptom so I pulled into the Target's parking lot and **** it off... pulled the code and surprise surprise .... I called every single Nissan Dealership in Chicago only one had it stock, the next morning I went to pick it up and back to Targets parking lot, it literally took me 15 min to swap the part and be back on the road... Ohh what a pleasant $300+ surprise was that... especially after replacing all ignition coils and plugs the week before with parts form DaveB
What a great way to start my summer and close to a grand for some parts :bustru n:

murphy's law if it ain't broke don't mess with it.....

Flanker84

My friend, almost every 2000-2001 3.0 Maximas will experience this problem. It's a "Must do" fix and before anything else happens just do the bypass coolant to the TB before your IACV kill your ECU.

You can get the piece with a dealership (Expensive as gold) or buy it from one of the many suppliers in the Internet (Courtesy parts, Parts Geek, and many more).

I bought one from Ebay for $120 bucks and it will be arrive today or tomorrow because the damn thing just screwed my car and the idle it's very VERY random.

PaulfromOlney

I had my car towed to the dealer because the ECU wouldnt recognize the car key as 'legitimate,' They said the ECU was dead. I researched the forum and concluded that the best solution was replace IACV, TPS and air temp sensor.
I sent my ECU out to be rebuilt (via EbaY) and expect they will replace the fried chips.
Wish I'd replaced the IAC as a preventive measure. I only have 200K miles!!

Darkrock

1. Verify IACV has continuity roughly 22ohms on each of the 6 pins
2. Disconnect EC motor mounts
3. Use procedure on page EC-111 (consult II) or EC-116 if you have a probe to program TSP
4. Rekey ECM and Keys (if replacing same part number)
5. Perform Idle relearn
6. Complete IACV/TB coolant bypass

Montego Murph

iTrader: (1)

I've read a lot of discussions on this...

I have a 2001 i30 with 81,000 miles on it. Should I replace the IACV as preventative maintenance, or is it too soon?

dimafed

My 2001 maxima started stalling if I don't hold the throttle. It does not do it every time, usually after warming up. No check engine light. Could it be the IACV without setting off the check engine?

cornholio

iTrader: (1)

it could be, my cel triggered for p0505 when i tried to gas it hard and keep idle. i reset the light and it never came back the next two weeks or so while i tried to diagnose and battle the problem.

i believe it could be other things too.

aongch

Bringing this back, now happening to my 2000 SE at 149K. What do you mean by "bypass coolant to the TB"? Is it the coolant leaking into it that possibly will fry the ECU? Is there a way to check the ECU at this time? Some replaced the IAC without ECU issues, some had to replace both.

Thanks, I'm about to do the work ASAP.

maxiiiboy

Guys, there are many threads that discuss this subject, but let me recap. There are two kinds of nasty problems that are inherent to our cars:

1. IACV Failure. The stepper motor wiring in the IACV is damaged by the coolant circulating through the IACV; its wiring goes short, in turn damaging the transistor drivers in the ECU. Usually, the ECU throws code P0505 (but not always, or not quickly enough). The cost of having this problem repaired at the dealer is high - typical $2000-2500 and up.
   
2. Electronic Engine Mount Failure. There are two electronic engine mounts (cars with Auto Xmission only) that control the stiffness of the mount. One mount is up front by the radiator, and the other one back by the firewall. Either mount can fail (go short), and again, in turn this damages the ECU.

You can avoid the above problems in the following manner:

1. Avoiding IACV Failure. Many of us have implemented "coolant bypass" for the IACV. This prevents the coolant from circulating through the IACV and thus damaging its wiring (which damages the ECU in turn). You can do this procedure in about two hours and there are several threads describing how to do it (search for "coolant bypass"). The other, more expensive solution is to replace the IACV with a new OEM unit. It seems that most IACV failures occur at 100k-120k miles, so the replacement should be done accordingly. Basically, the expected lifetime of the IACV seals/wiring is about 100k miles, but it varies from car to car.
2. Avoiding "Engine Mount frying the ECU". The simplest solution is to disconnect your electronic engine mounts. Again, many threads describe how to do it, and at least one of them has pictures showing the location of EM connectors (they are brown, under and a bit in-front-of the air intake/TB). Should your mount fail and damage your ECU, the repair (by a dealer) is very expensive - just as above.

I have implemented both "IACV Coolant Bypass" and "Electronic Mount Disconnect", so feel free to ask questions. However, do the suggested searches first and read up on what's already available and known.

aongch

About this part, once I get the P505, does this mean the ECU has shorted already, or still possible just the IAC is bad and ECU still saveable?

I'm about to dive in, got the Hitachi IAC ready to install, but hoping this is all I need to do. The idle relearn with new ECU, etc etc could be avoided I hope.

Thanks again for the responses, and sorry don't have much time to do all the searches. Saw a 6 part video already on the fixes, that was a lot of work.

cornholio

iTrader: (1)

it doesn't necessarily mean the ecu is bad. i recommend pulling it out and doing a visual examination, pretty simple to do.


not sure why you quoted me maxiidude, my issue was sorted months ago (primarily from searching on my own). maybe meant for someone else or i guess it makes me cool or something. good summary tho

maxiiiboy

I think the only way to tell is to take the ECU out and have a look at the board. Also, I remember reading a story on this forum where one of the members replaced the IACV before fixing the ECU. And guess what - the new IACV was somehow damaged by the bad ECU. I don't fully understand how & why this happened (although I have a theory), but I strongly suggest to do things in the following order:

1. Verify the ECU is good. Remove the ECU board and check for burns/smell/etc. - it's usually pretty obvious. If bad, fix it by replacing the burnt Mosfet transistors on the ECU board. Alternately, get a good and inexpensive ECU (Courtesy Nissan sells some refurbished ones for around $500-600) but you'll have to have your keys reprogrammed, etc; that's a hassle and a big drawback of this second solution.
2. Once you are sure that your ECU is good, you can replace your IACV.
3. To sum it up, during this repair process, you must avoid the situation where one of the (IACV, ECU) parts is bad, as either one could damage the other.

aongch

This is a good tip, thx. I'll check the ECU first. Such a pain to remove the 4 phillips screws holding the ECU box, will report back condition of the ECU.

If bad, is this a reputable place? I'd rather fix my current ECU than having to buy new and do the complete reprogramming.

http://circuitboardmedics.com/maxima-ecm-repair/

aongch

Well, pulled the ECM and ECU board looks clean, no burn marks anywhere. Next steps? Should I install the new OEM IAC valve and hope the ECU won't short circuit? Thanks, that ECM sure was a pain to remove!









Backside (dark blue swirl looks like dye)

maxiiiboy

You have several options: a) You can just install a new IACV - it should last a while; b) You can install new IACV and implement Coolant Bypass, this should be more secure as there would be no coolant eating on your IACV wiring; c) Install new IACV and add fuses to protect the ECU; this would give you the best security (see the discussion on this thread https://maxima.org/forums/5th-genera...ml#post9008986 ).

aongch

Yup, following that 'fried ecu' thread, lots of good info. I'm certainly doing option (b) for now, doing the bypass! Will report back. Thanks.

Still love the way this 5th gen drives, easy shifting manual, with minor susp upgrades like stiffer springs, 5-way Illuminas, Stillen rear bar, rails corners!

BTW, my ECM was held on not by 8mm screws but Phillips heads, what at b***** and I'm the orig owner so it has never been serviced before.

aongch

Going to do the coolant bypass next. Searched and so far it is as simple as this? "Procedure: Purchased 5/16" brass split hose mender with the claw backs. Disconnected each hose from each side of the IACV/TB and joined each to the brass mender and clamped with existing. Capped each IACV port with 3/8" ID black chair tips and these aren't as snug as I would have liked but not certain I even need any but it looks more finished. Fired up with no issues."

This was found in thread below, let me know if there is more to it, looks to be an easy procedure:
https://maxima.org/forums/5th-genera...nt-bypass.html

maxiiiboy

You needn't to purchase any brass splits. Apart from removing the air intake, it's very simple: There are two hoses coming in and out of the IACV/TB - let's call the inflow hose H1 and the outflow hose H2:

1. Disconnect the destination end of H1 (the one on the IACV) from the IACV.
2. Disconnect the destination end of H2 (the end not on the IACV).
3. Connect the end of H1 you just freed in #1 above to the engine port you just freed in #2 above. At this point, you just by-passed the IACV.
4. Now, you may want to do something about H2 - its one end is connected to the IACV, the other end is hanging free. Most people suggest looping it back to the other IACV port that is now free. You should try to blow out any coolant remaining in the IACV before closing the loop. Alternately, don't close the loop just yet, and let the coolant dry out first (that's what I did).

The hoses happen to be long enough that you can do all this without purchasing any brass splits, new hoses, and not even clamps. What you may need though is a good set of hose pliers to move the clamps and hoses around. I bought some very good ones (and very inexpensive) at HarborFreight tools.

nissan2001

I am having the same problem with my 2001 Nissan maxima. She I starting up my car I have to press on the gas for like 2 seconds so it doesn't shut off. I have no service engine soon light on. Once the car is warm I can turn off the car and turn it back on with no problem. The car runs perfect after starting it up. I have replaced the IACV, throttle position sensor, engine mount, air charge temperature and my ECU. I don't what else I need to replace or fix so I don't have to press the gas when first starting up my car?..

Max_5gen

iTrader: (2)

Did you pull the error codes? Check for intake leaks and check your CTS.

maxiiiboy

Also, clean your Crankshaft Position Sensor.

aongch

I went through the bypass procedure, hooked up the new IACV and plugged the ECU back in after checking for any burnt areas (whew, none) and so far no issues. No idle relearn even. Idle is perfect at about 700, no stumbling or cutting out. But.....

Strange thing, my cold air now does not come in, only warm/hot air through the vents. A/C still works but again, no cold air channeled to the vents. Did I bump and disconnected something? All seems to be intact in engine comp and under the dash. Is there a connector, plug, switch somewhere nearby that I could have bumped loose?

Any ideas??

aongch

Does the ECM control any of the cold/hot air circulation through the vents? Still stumped.

maxiiiboy

You did not tell us whether you have Auto or Manual temperature control. In either case, check the fuses. If they are OK, follow the diagnostic procedure in the FSM (p. HA-61).

aongch

Sorry, I have the Manual temp controls, will check the fuses and the procedure. Thank for the tip.

Btw, I posted a sep thread since my IACV is fixed, but strange issue.

Harquebus

I am going through the IACV issue right now after having variable and rough idling for a few months and then a complete failure to idle at all without judicious gas pedal intervention. As I read on another thread here about a "burnt smell" in the cabin, I was grieved to learn that this indeed indicates that the faulty IACV has burned out the ECM. This was confirmed by the stealership calling me back with the diagnosis so that was a rude realization.

The stealership (I'll find a good indie later on) told me the diagnostic results were, "The IACV shows high resistance - the ECM doesn't recognize the IACV which caused the ECM to short out."

However, I refuse to pay the exorbitant stealer pricing so am now sourcing a remanufactured ECM and a new IACV.

Question: is the IACV specific to either manual or auto transmission? The ECM is specific and has a different part number. I have the manual trans and SE version.

Thanks. Great thread here with very astute posts.

~Harq

EDIT: The IACv is NOT specific -- it is "one size fits all".

maxiiiboy

Yes, the IACV is the same for both MT or AT Maximas. You can get it for about $241 from courtesy Nissan.

Harquebus

I read that an OEM IACV is preferable but I sourced one locally at an AutoZone. Rockauto has them the cheapest I've seen. I've had great success with AutoZone no matter where I am and my other car's a SAAB, so...

Incidentally, I have sent my ECM to Circuit Board Medics for repair. Great communication with them so far by phone and email telling me my package has been received and will be ready for return shipment tomorrow. All for $199 which is absolutely outstanding. Prior to that I was doing a lot of legwork to find one locally but either there were none in stock/none in their catalogs or very long wait times for a re-manufactured one which is what they all are these days.

The car's 15 years old...

maxiiiboy

Hope things work out for you with Circuit Board Medics; they got some poor reviews here on the org. I have heard good things about the guys in Florida (http://www.avproecm.com/ ) - the best thing being that they will upgrade your ECU by adding fuses; prices are $160 for fix, $240 ffor ix + fusing. All with lifetime warranty. There is also a good outfit advertising on eBay (http://www.ebay.com/itm/00-01-NISSAN-MAXIMA-Computer-REPAIR-KIT-ECM-ECU-2000-2001-3T-A56-Q79-/230749169527?rmvSB=true ). In either case, you want to read this thread https://maxima.org/forums/5th-genera...seconds-6.html .

Harquebus

Update on the ECU: Just received a call from the outfit. They are returning the ECU and refunding me minus a $50 diagnostic fee because essentially they could not find anything wrong with it. They hooked it up to an IACV they have on their test bench and it worked fine. The P0505 code does not manifest itself. I listed other codes besides 0505 (P0100, P1320, P1706, P0325) but those are beyond the services they provide.

Harquebus

The plot thickens. After talking to Circuit Board Medics as they were in the process of returning my ECU, they told me the ECU checked out fine; "tested well without P0505 (did not manifest itself), controlled the IACV well, no visible damage." So I received it today and sent it to the service center.

I was just called with word that the car is not ready because the ECU is still bad. The service woman says it has "bad drivers" which are not working properly.

Does anyone know what this means? How do I get this fixed? Help!

maxiiiboy

"Driver" is a part of the ECU program responsible for controlling a certain device such as the IACV, or TPS, etc. This problem, and other like it, can be fixed by "reflashing" the ECU - i.e., by up loading the latest/current program into it. Only the dealer can do it.

Harquebus

Thanks for the quick reply. So are you saying it is strictly a 'reflashing' procedure and not a hardware problem? CBM found nothing wrong with it of course.

My skepticism tells me they're not being entirely truthful with me but maybe the tech on duty just doesn't know to do anything beyond reading the diagnostic tool telling him the drivers are bad? Shall I simply tell the service place to 'reflash' it?

maxiiiboy

No, I am not saying that. I just explained what the term "bad drivers" means.
Whether the lady is right/wrong, I have no idea. Re. CBM, I told you earlier that their reputation wasn't that great.

P.S. Reflashing is certainly a good idea. How much will they charge you?