ButtaMax

iTrader: (7)

Its the IVAC bro, call Dave B $2fiddy!!

qwerty652

I'm having this similar issue: (2001 Nissan Maxima - 120K)

P0505 code - car would die when starting cold, unless the engine was revved up for a few seconds. Replaced the IACV and cleaned the throttle body and MAF.

Result: Same code, but now it will start no problem, but the idle will shoot up to around 2000 rpm and then will fluctuate up and down. When you put it in gear, it is driveable, but the rpms still seem high and do fluctuate when you come to a stop.

What next? Is there something wrong with my ECU? Does it need to be reprogrammed or (hopefully not) replaced? Thanks in advance!

duanes7

My car also dies on startup. But if I give it a little gas for a couple of seconds it then stays running. Idles up/down with ac on/off, but idles a little low at lights.

Inside of ECU looks fine.

Replaced all the intake gaskets this weekend. Alos found coolant seaping around IACV to TB gasket. Replaced that gasket as well. Car would not idle at startup prior to gaskets replacement.

Is it possible that my IACV is in the process of going bad and is just slow to respond? Could the coolant have damaged it?

Oh, and I have no codes now. Had o2 codes before the gasket replacement.

duanes7

forgot to subscribe...

qwerty652

Well, took it into the dealer (they told me that they could hopefully just reprogram the ECM), but it turns out it is shot. Price quoted was $1200 for a new one!

Wow, that is pricey.

Is there a good reliable place to get a used/refurb ECM online? If anyone knows of any, please post!

MikeJL

The IACV is the problem generally if you start and then immediately stall. It will not exhibit this behavior every time but after a while it will be nearly every time you go to start the car. Do this: Use throttle body cleaner and inject it into the air intake hose fitting in the IACV body. I have 4th gen and I don't know what your's looks like but it most likely is the same. This should clean it up.

If not, get a gasket, remove the IACV (3 screws I remember) and clean it out of the body.

Do this to be sure that the IACV is the problem. Start the car when cold. You should see RPMs at 11K or so and watch the RPMs as the engine warms. You should see "steps" in the RPM decrease until you reach idle. This tells you that the IACV is responding to engine conditions and is working to reduce aif flow into the engine to reduce idle. Until you see this the IACV is suspect.

Also, you may be able to start the car if you turn on the ac before you start. This will open an auxilliary solenoid valve the let's more air in to the engine to bump up idle to compensate for compressor load.

Either way, IACV should be cleaned periodically and once you see the results you will be able to diagnose it easily in the future.

Mike

duanes7

After I start my car (whether normally or having to give it gas), the idle does step down as it should. Seems the IACV is working.

I've had my 5th gen IACV (2000 I30) completely apart and it has both a stepper motor and an internal "flapper" assembly. There are square air ports that join the TB both before and after the plate and 2 coolant hoses so coolant can flow through the center of the IACV body. There is a 1/2" round hole passage between the external and intake side square ports.

The stepper motor has a tapered plug that points directly at the 1/2" hole ans probably moves in and out, thus adjusting the amount of air bypassing the TB.

The flapper is about 1.5" long, 3/16" at its narrowest and 1/2" at its widest. There is a spring or coil that slots into the flapper on one end and into a slot on the IACV body on the other. The assembly is on the intake side and lies across the air stream coming through the 1/2" hole. Seems that as it rotates it presents more or less of an obstruction to air flow. As the flapper has no electrical connection, I'm assuming the coil is some kind of bymetallic part that winds/unwinds with the temp and changes the pitch of the flapper or it's a spring that lets the flapper simply respond to the amount of air that the stepper is letting through.

Again, seems my IACV is working once the engine is running. This weekend I will pull it again and check the resistence.

Anyone have an idea what the time is supposed to be for the stepper to drive from fully open to fully closed? Or what length the shaft/plug assembly is supposed to be at each position?

qwerty652

got my ECU repaired for $70 at autoecu.com... just got it back and put it in, works great. Much better alternative to buying a used or new ECU!

thesuntoucher

Make sure the IACV isnt going bad, sometimes cleaning it wont help. That kick my @$$.

dcwilliam

I have a 2001 Maxima, the car would die right after starting unless I held the throttle down for a couple seconds then it would run fine. I like many eventually got a P0505 code, replaced my IAC, TPS, and while replacing those sent my blown chip on ECM to get repaired. After putting it all back together it still continued to die. I had the dealer look at it who told me that my radiator and thermostat was bad(nothing to do with the dieing car) so I replaced that, Car still dies. I replace the camshaft and both crankshaft position sensors, still dies. I took the car back to the dealership and now tells me that my starter is dieing and has a dead spot in it and I need a new camshaft position sensor and that there is oil in the camshaft position sensor harness(once again I cant see this fixing my dieing problem) I replaced the starter and cleaned the harness and it continues to die and after I got it back from the dealer when i turn the car off I hear a what seems to be a motor running, it wont stop unless I disconnect the battery(maybe the oil pump)

so 2 questions:
1.How do I fix the dieing car?

2. Has anyone had this small motor running sound before?

Suzesisk

I have a 2k Max with 210k miles. I've replaced the alternator then the starter. Soon after I noticed PWRs steering leaked. Haven't replaced that yet but here's the question that relates to this thread....don't know what to do nxt. Getting ready to enter on ramp and the idle dropped to nothing. Have to press gas to keep it up and running. Now the odd thing is at first it did this periodically it sat for about 3 months. Didn't have time or $ to repair. I've taken it to dealership. They've cleaned the throttle body but it didn't help, in fact now the prob is constant instead of periodic. We've purchased a iac to replace but as I've researched this site I'm wondering...do I need to "relearn" it before replacing? If so can that be done by me or do I have to take to dealership? Sorry so long winded but it's just me and the repair manuel.

maxiiiboy

Instead of doing the idle re-learn, you can just disconnect the battery (both terminals) for at least 24 hours (some people think 3 days are needed). The ECU will then relearn automatically, on its own.

Re. the stalling, the prime suspects are the MAF and the IACV. I would start with the MAF - I would clean it first, and if that did not work, I would replace it.

Thebull8913

Hey ur got ur car fix?...my nissan is giving me same problem...sucks!