I had a previous post "Can't Remove MAF" (thread p6424280), but the problem has evolved to something different, so I thought I'd start a new thread, as I could not find anything in the I30 forum that dealt with this specifically...

I ended up taking the 2001 I30 to the dealer to diagnose the rough idle and cause for the car to idle down/die while at stop.

They say I need a new Idle Air Control Valve (over $700), and possibly a new ECM (over $2000), but they won't know that until the IACV is replaced.

Ouch! I've heard that a bad IACV can short out the ECM, but how likely is this really?

I think I could do the IACV myself, or at least get a better deal at another garage, now that I know what the issue is.

What are my options? Can I replace the IACV without much issue? Where do you recommend purchasing the part if I do? My two choices would be O'Reilly or Autozone. Any reprogramming required afterwards?

Then there's the ECM. Not sure where it lives or how hard it is to get to, but where can I grab a new or rebuilt one?

I don't want to go for the IACV without at least having my options lined up for the ECM, if needed.

Bottom line, what's realistic here? Don't want a repair that's going to be more than book value for the car.

I know this is a lot of info, but I'm desperate at this point.

OK I already told you that this was your problem in the other thread. The IACV is not $700 even with install labor. Mitchells labor time is 1.7hrs to install and reset idle. I do it all the time cause people don't listen to me when I try to sell them the gasket, that fails, that is only $3. You need to change the IACV and have the dealer attempt to reset the idle. If the idle does not reset you'll need the ecm. If it is the ecm you can have it rebuilt for around $200 form a shop in Texas, can't think of it right off but we send the ecm's to them all the time and they usually have a quick turn around. Usually you can stick your head down there and smell for a burnt electrical odor if it is bad but if not then the reset attempt is the only other way to tell.

Here is the part and price from courtesy parts
http://www.courtesyparts.com/23781u-iac ... 93630.html

Thanks, Outcast. I DID give you credit in the other post. Problem is, a guy reads through tons of forums, Google results, etc. and you'll see tons of different answers. The more you research, the more confusing it gets. I thought it was worth the $75 bucks to have the dealer hook it up and look it over. Plus, the original mechanic said the IAC was fine...

I got an IAC from Autozone and had a hell of a time getting connectors and hoses off, but the throttle body is out (which I went ahead and cleaned). Am waiting on a new TB gasket before reassembly.

Here's the big question: everything I read says that if the ECM fried, then replacing the IAC without fixing will fry the new IAC... Yuck.

So after I get everything back together under the hood, I want to inspect the ECM for visible damage before i apply power to anything. But my gut says to go ahead and replace or send out the ECM to be safe - I can't afford to replace the IAC twice.

Thoughts?

Also see where the motor mounts are a major cause of ECM failure in these cars. Am tempted to just disconnect them.

Saw something else that even said to replace the throttle position sensor along with the IAC... Jeez. Really?

Thanks, again,
DBB

Motor mount can do it to but it's rare. If you replace the IACV and the computer is bad it will not fry the new IACV. The IACV shorts the ECM because of coolant that gets past the old seal and on the electric motor.

I can't tell you how many posts I've read where a fried ECM has ruined a brand new IAC.

With a new ECM, I'd have to have the keys programmed before I could even start the thing. Is there a way to test the ECM? Can I take the ECM to a regular garage for this, or am I back to the dealer?

Honestly the only way I test them is to use Consult if I don't smell the burnt electrical odor. And as a tech I have never seen or heard of the ecm shorting the IACV it's always the other way around. Even the shop that rebuilds them for us always sends a slip with it telling us to replace the IACV cause the ECM will get damaged again if not replaced.

Okay... I'll defer to you.

But in the shop, do you always test the ECM with Consult following an IAC replacement?

So without access to Consult, after I replace the IAC, I'll pull the ECM and look for visible damage. If I see none, you're saying it's safe to power up the car, then?

If I need to rebuild, the service you use wouldn't happen to be AutoComp Technologies in Houston, would it? If not, do you think you could find the service you use? There's a repair service local to Dallas here, but a technician told me that rebuilt ECMs from them fail to program, more times than not.

Thanks, Outkast.

You'll usually see a burnt curcuit on the board when you pull the ECM but can smell it if you just stick your head down there and sniff. It's out of Houston, cause that's what one of the boxes said the last time I did one and again I've never had a problem with theres not programming after the repair. You can even get ECM's off ebay too for $200 to if you want it faster.

I called the place in houston i mentioned. They don't repair ECMs for the I30, but would sell me one off the shelf.

With a new ECM, I'd have to carry it to the dealer to have my keys reprogrammed before the ignition would work, then after it's installed, take the car back to the dealer again to have them then finish up what programming couldn't be done before, correct?

Part numbers for the I30 and Maxima are the same, google it. When they program the keys, they will set idle as well. Anything else would be ripping you off

I'm a bit confused here...

The keys have to be programmed to the new ECM, or the keys will not work in the ignition to start the car, correct? So, from what I've been told, I can take the ECM (just the ECM; not installed in the car) and my keys to the dealer (the only ones who can do this, apparently) to get this done.

Once the keys are operational, the new ECM would be installed in the car, and then the car driven to the dealership to do the idle relearn, and whatever other functions have to be programmed that requires the ECM to be installed in the vehicle.

So, two trips/two programming efforts.

What am I missing?

I've replaced the IAC, and everything is back together. Disconnected the mounts while I was at it.

Pulled the ECM and inspected it, and there is absolutely no sign of damage, nor does it smell burnt, so I put it back in. Started the car and let it sit idling in park for a while, then drove around for about 10 minutes.

I pulled back in my garage and let it sit at idle for a while longer, as the original problem only seemed to happen when it was good and warm.

Idle RPM is about 700, but every 30 seconds or so, it still shudders and dips to 500-600 RPM, then returns to 700. But it didn't die during the dip this time. I'll drive it around this weekend to see if that will still happen.

Do I still have a possible ECM problem, or has the IAC screwed up again? Bear in mind that I have't yet done the idle relearn procedure.

Pulled the ECM and inspected it, and there is absolutely no sign of damage, nor does it smell burnt, so I put it back in. Started the car and let it sit idling in park for a while, then drove around for about 10 minutes.

The thing to take a very close look at in the ECU is the STA509A Mosfet, it's a black 10 pin SIP plastic part about an inch long and third of an inch tall located near the connector. If the chip has overheated it sometimes blows a chunk of the plastic casing off, or the casing swells or cracks or discolors. If the Mosfet package still looks *pristine* (like other ones in the ECU), and you see no signs of burnt circuit traces leading to it (on the top or bottom of the board), then it may well be the ECU is ok.

Since you report that your idle is inconsistent, I'd have it scanned for codes at AutoZone to make sure the P0505 code is gone, and that no other codes are present. It may well be you need to do the idle relearn procedure, which is something you can do yourself (the manual gives instructions for doing this w/o the Consult tester, so you don't have to take it in to get this done).

Where are you located?

A couple of summers ago I bought a 99 I30 for $300 from a lady that had given up on getting the bad ECU fixed. The car would not run and she had spent a bunch of money chasing a "tire store" fuel system misdiagnosis. I stopped by Pick-and-Pull on the way to pick up the car and got an ECM for $30 from a wrecked 99 Maxima along with the IACV from the same car. I think the IACV cost $25. I could tell from the wrecked Maxima's interior and engine compartment that car received good care before it was wrecked. I cleaned the IACV then tested it to determine it was good before installing it. At that time I didn't realize the IACV issue was most likely to occur on the 5th gen.

To get NATS reprogrammed, I had the car towed to the dealer where they took Consult and reprogrammed it to match the keys or vice versa. It cost one hour of labor $115 for the reprogramming.

When I see a relatively clean Maxima with under 200,000 miles at the salvage yard with no explainable reason for the car being salvaged, I think it must have been caused by one following failure reasons:

1) Failed ECM from either the electric front motor mount or IACV (5th gen)

2) Owner gave up and threw in the towel after several rounds with a failed MAF, IACV or both.

3) Transmission failure due to fluid neglect.

After it was all said and done, I spent around $600 on car, used parts, towing, and reprogramming on the I30.

We don't want your I30 to be the next salvage yard casualty.

Pilm wrote:

The thing to take a very close look at in the ECU is the STA509A Mosfet

Yeah, I've seen this chip mentioned; some even replace it on their own. Mine was undamaged, as were the circuit traces under/around it.

Make sure the P0505 code is gone, and that no other codes are present.

I never had the P0505 code. The one that showed up was the too lean P0174. I paid the dealership $80 for a full diagnosis. They said it was the IACV.

Sounds like you did great on on the used I30. $600. I doubt if I would be that lucky... LOL

OwnerCS wrote:

Where are you located?

Dallas

To get NATS reprogrammed, I had the car towed to the dealer

Was trying to avoid this. Turns out, my ECM must be okay, thank goodness. If I would have had to replace it, I probably would have removed the panels and unbolted it from the bracket, then driven to the dealer and pop the new one in for programming in their parking lot once I got there...

BUT, since my last post, I think I have some good news to report...

I drove the car around some more and discovered it still died on me when warmed up. Limped it home and figured with nothing to lose, I'd use more force to try and get the MAF sensor out again (I had originally started by trying to remove the MAF sensor but couldn't get it out).

But first, I pulled the MAF connector off and let it idle for quite a while. Not only did it not die, but the "idle dips" no longer occurred. Got the P0100 MAF codes, as expected, though...

So I pulled the MAF sensor out - I really had to pry around hard on it, and chewed it up around the edges, but it finally came out.

The sensor wire was pretty dirty, so I shot the whole thing with MAF cleaner in short bursts until shiny, let it dry and reinstalled.

I cleared the P0100 codes and again let the car idle for quite a while. Exhaust really smelled, and after a bit, I got the too rich P0172 code.

Ran through an idle relearn procedure (RPM shot up briefly when the Throttle Position Sensor connector was removed). When finished with the procedure, the idle RPM was pretty much unchanged from where it was before (600-700), but the idle had smoothed out - the occasional RPM dips were gone. The P0172 code went away on its own, too.

Guardedly optimistic, but I've driven around on some errands, and it appears that my problems have been fixed! The idle is smooth and steady.

Speaking of misdiagnosis, now I'm wondering if the MAF was the culprit the whole time, and if the dealer's bad IACV diagnosis was wrong? Regardless, $225 in parts (IACV, Throttle Body gasket, MAF and TF cleaner), $80 for the dealer's diagnosis and my time, and it looks like I'm back on the road.

Sure beats the dealer estimate of > $700, with potential $2000 ECM they quoted.

One thing; the dealer's $80 was a full diagnosis, so I have some other things to look at now, like a power steering leak, and cracked drive belts...

Thanks, everyone!

I have done this twice before. If the engine does not die when removing the MAF connector
then the MAF is probably bad.

Your price is too good. I don't think you got a new IACV and
MAF. The MAF by itself is over $200 even at Oreilley's, Auto Zone etc. Something got cleaned and replaced-probably the MAF.

The IACV collects a lot of carbon and get stopped up. A multimeter can show it as working when
it really isn't. You can open it up and get the carbon out of it.

NutriaforBreakfast wrote:Your price is too good. I don't think you got a new IACV and MAF. The MAF by itself is over $200 even at Oreilley's, Auto Zone etc. Something got cleaned and replaced-probably the MAF.

No, you may have misread; sorry if I wasn't clear. I only replaced the IACV, and just cleaned and reinstalled the MAF sensor. The 'MAF' in my total costs was referring to the can of MAF cleaner, along with the can of throttle body cleaner.

The IACV collects a lot of carbon and get stopped up. A multimeter can show it as working when it really isn't. You can open it up and get the carbon out of it.

The IACV was pretty fouled up with carbon. Maybe I should clean it out and put a meter to it to see how it reads for curiosity's sake. I could kick myself for not wailing on the MAF sensor to get it out when I tried that first, though. I'm half willing to bet there was nothing wrong with the IACV, and I could have saved myself a whole lot of trouble and money simply by cleaning the MAF.

So how does the dealership test and make the determination that the IACV is bad?

In the end though, it was an experience. I've saved quite a bit of money, and I've got a nice clean throttle body to boot, along with the satisfaction of doing everything myself. The help and info in these forums are worth gold.

Of course I wouldn't be looking at it that way if the car was still out of commission... Lol

A big thanks to everyone who replied!

Get the carbon out of the IACV and it should be ok. Use electronic cleaner on nearly everything
under the hood-degreaser is just too aggressive and redneck.

Consider cleaning the IACV and the MAF as a general maintenance item like the spark plugs,
air filter etc.

Im having the p0505 dance now. I had a p0400 egr flo malf when I got tis car -00 i30- about 2 months ago. next came the 1126, 0172, and then the p0505, I cleaned the egr tube which was packed solid of carbon which Im familiar with from maximas. I then replace coolant temp sens, egrv, and iac. Well 1126 n 0400 are gone and the 0505 is back. I did check the ecm 3 times and its good. Well I put back old iac with new gasket after I cleaned and tested it (since it was n sync with ecm) and it runs perfect....except it stalls now...a lot. It did before I unclogged egr tube n I thought egr was culprit but u guess not, I did unplug MAFS and car ran ok, shuttered past like 6k rpms tho. Idid clean mafs and on way to replace. It sounds like theres a vac leak somewhere. With the stalling however I removed vac tube to air control valve just behind throttle bell crank and it ran fine. It also stalls when I chock wheels left and right in park. There is significant power steering leakage but cant find. I think maybe pumps sealing gaskets but it howls pretty loud when I turn. How do I remove the p0505. Got car in Jersey and Im in NY and cant get a NYS inspection until light off. I keep getting I to 3 codes all for p0505. The motor mounts been disconnected since I got car. I don't think the iac went before I replaced egrv n iacv the 1st time. previous owner drove with p0400 for so long that the p0505 came on literally 2 days before I cleaned egr. The new iac caused massive ide problems and refused non-consult2 relearn. when I swapped old iac it drove so quiet and ice and idle beautifully. I guess what Im asking is an ecm be fried if its sexy as hell inside, no burnt chips ( I no which ones to look for), burnt odor, nothing. Or can a P0505 be triggered by other malfunctions. Can a bad MAFS thro a p0505 or cause the IACV to not work properly? Please help me out. I got a lot of years working with cars so you can talk direct to me. Im pretty sure theres no coolant in iacv motor and almost sure ECM is ok. EGR is new and works fine. Iacv harness is hot and iacv motor works. I have a suspicion either mafs or an air leak has something to do with it. thanks.

Welcome to NICO.

You can find info and diagnostics for P0505 starting on page EL-458. http://www.nicoclub.com/FSM/I30/2000%20I30/EC.pdf

Be sure to look at the vacuum diagnostics beginning with step 4 (since you mentioned a possible vacuum leak sound).

[[/img][/img][quote="DBB1"]I had a previous post "Can't Remove MAF" (thread p6424280), but the problem has evolved to something different, so I thought I'd start a new thread, as I could not find anything in the I30 forum that dealt with this specifically...

I ended up taking the 2001 I30 to the dealer to diagnose the rough idle and cause for the car to idle down/die while at stop.

They say I need a new Idle Air Control Valve (over $700), and possibly a new ECM (over $2000), but they won't know that until the IACV is replaced.

Ouch! I've heard that a bad IACV can short out the ECM, but how likely is this really?

I think I could do the IACV myself, or at least get a better deal at another garage, now that I know what the issue is.

What are my options? Can I replace the IACV without much issue? Where do you recommend purchasing the part if I do? My two choices would be O'Reilly or Autozone. Any reprogramming required afterwards?

Then there's the ECM. Not sure where it lives or how hard it is to get to, but where can I grab a new or rebuilt one?

I don't want to go for the IACV without at least having my options lined up for the ECM, if needed.

Bottom line, what's realistic here? Don't want a repair that's going to be more than book value for the car.

I know this is a lot of info, but I'm desperate at this point.[/quo

I replaced my IACV on my 2001 infiniti i30 and it did burn up a chip on the ECM ...I have replaced the ECM myself and I am a woman. Now I have to reprogram the key. Open for suggestions ..

I replaced my IACV on my 2001 infiniti i30 and it did burn up a chip on the ECM ...I have replaced the ECM myself and I am a woman. Now I have to reprogram the key. Open for suggestions ..

DBB1 wrote:Thanks, Outcast. I DID give you credit in the other post. Problem is, a guy reads through tons of forums, Google results, etc. and you'll see tons of different answers. The more you research, the more confusing it gets. I thought it was worth the $75 bucks to have the dealer hook it up and look it over. Plus, the original mechanic said the IAC was fine...

I got an IAC from Autozone and had a hell of a time getting connectors and hoses off, but the throttle body is out (which I went ahead and cleaned). Am waiting on a new TB gasket before reassembly.

Here's the big question: everything I read says that if the ECM fried, then replacing the IAC without fixing will fry the new IAC... Yuck.

So after I get everything back together under the hood, I want to inspect the ECM for visible damage before i apply power to anything. But my gut says to go ahead and replace or send out the ECM to be safe - I can't afford to replace the IAC twice.

Thoughts?

Also see where the motor mounts are a major cause of ECM failure in these cars. Am tempted to just disconnect them.

Saw something else that even said to replace the throttle position sensor along with the IAC... Jeez. Really?

Thanks, again,
DBB

I REPLACED THE IAC AND FOUND THE ECM AND ONE OF MY CHIPS ON THE CIRCUIT WAS FRIED..(YES I AM A FEMALE) FOUND ALL THE PARTS ON EBAY BUT NOW ITS THROWING THE P0430 CODE AND THIS WAS RIGHT AFTER I REPLACED THE ECM. I cleared the code drove it for about a day...running poorly. I rescanned (no engine light on) now no code but its no reading it ....has good connection. My question is since I didnt do the reset procedure /relearning...would it throw codes out even if there isn't anything wrong w the what the codes are throwing out? Still running poorly./
Any advice would be very helpful and appreciated.

After reading through a bunch of myths about IACV, it looks like many don't understand the function of nissan IACV. Here is a short explanation.
IACV stepper motor has 4 coils at ca. 20 Ohm each. When they short ( it goes down to almost 0), control transistor in ecm cannot handle a lot of current, and burns out, and cannot control idle anymore, which leads to P0500. It's very easy to test the motor: just remove 2 small screws and pull out the motor from idle housing. The plug has 6 terminals, the middle ones - power, the other 4 - for coils. Take your goddamn voltemeter, set to ohms to 200 ohm scale, and test resistance. if it 2, 3, 10 , no restance, it's not good, shorted or burned out. It should be above 20 OHm.Put a new one in(make sure to check coils!) and test the signal from ecm with a scope, but actually i's just easier to remove ecm and just open a cover to look at pcb.. And you don't have to replace the whole housing, if it doesn't leak.

Is it safe to disconnect the ECM and check if any burnt chips? I read somewhere that when disconnecting the ECM, the car will lock and the keys need to be reprogrammed.

I want to make sure I can disconnect the ECM safely, check it, and be able to connect it back without any reprogramming issues. Thanks.

Also, is an aftermarket IACV good? Or should I stick with the Hitachi brand?

Yes, it is absolutely safe to disconnect battery power, remove the ECM, and check it for any burnt chips.

You can use an aftermarket IACV, but why try to save a few dollars and risk that it will burn your ECU? You can get the OEM IACV for only $231 + shipping (see http://nissanpartsasap.com/nissanparts/ ... atalogID=0 ).