Monty51

Working on a car for a friend. He has a 2001 Maxima SE which he bought used, and while it's generally a good car, it won't idle. As soon as he takes his foot off the gas pedal it revs down and stops. Otherwise the engine runs smooth, doesn't blow any smoke or run rough. He's been driving it around for some time by keeping the revs up. He took it in to the Nissan dealer and they said something was wrong with the throttle body, but not being a mecahanic, he can't remember just what it was. They quoted hiim $1,800 to fix it, which is what he paid for the car, so I can understand his reluctance to pay it. Can anyone suggest an approach to troubleshooting this problem? I'm not experienced with Nissan products and am not sure where to start with this one.

Thanks

D.Stillwell

Sorry to hear this man. Sounds like a bad IACV (idle air control valve) and those are also known to fry the ECU mosfet chip when they go bad and not replaced in time.

That said, if it was just a bad IACV the quote wouldn't be nowhere near $1800 or even close to a thousand. So with this quote your friend got, I'm assuming the ECU got fried by the bad IACV.

It can be possible to solder in a new mosfet chip, if the ECU is still in good shape otherwise. Doing that can be done for cheap, and then get a new IACV. If the ECU isn't salvageable, then I'm afraid you're screwed.

But wait, DONT PAY DEALERSHIP PRICES. Even if the ECU is done for, you guys can go to a junkyard and pull one from a 5th gen Maxima. Same for the IACV really, although considering those things like to stick I'd prefer a brand new IACV.

Monty51

ECU...is that the same as the ECM (Electronic Control Module)?

D.Stillwell

^^^ Those two lines don't go well together. But yeah, ECM = ECU

WTF?

Pull a vacuum line, see if it idles.

Monty51

"Pull a vacuum line, see if it idles." Interesting. What would that tell me if it did idle?

D.Stillwell

Monty51

I see, I have to separate the jokers from the well-intended.

Ok then, if the ECU was fried, I'd expect numerous things to be wrong with the car, which doesn't seem to be the case. Let's say I pull the wiring form the IACV and nothing changes, can I assume the IACV is bad?

candicurtis

We just bought a 2000 Maxima SE. Worked fine for a few days. Then noticed a leak in a hose next to the throttle area. We fixed the leak and it started dying. Same as you. I did extensive research on this forum.
I started to think the same thing. IACV as people were suggesting.
However, my husband started playing with the throttle controls, adjusting them. He thinks the previous owner messed with them to keep the revs up. After readjusting the car is idling correctly, for now anyways.
Maybe try that first?

Monty51

Thanks cancicurtis, I'll look at that. Amazing how fixing a leak can result in worse performance. My apologies to WTF? for thinking he/she was just messing around.

D.Stillwell

Lets see if I can help some more.

First thing you wanna do is DON'T listen to this person above ^^^, messing with the throttle cables can REALLY mess up your idle.

Then, also forget about the vaacum lines. No way that fixing a leak can result in worse performance. That's an oxymoron. All that means is these people had other underlying problems.

Now, that said let me get to the important info.

When the IACV goes bad it shorts back to the ECU, it shorts the mosfet chip. That is solely responsible for idle control, so you may not have any other issues with the car besides that. Also, a bad IACV can short the mosfet very quickly, so if you get a bad replacement IACV this can happen again. This is why I said you should not get a junkyard IAC, buy one new. Junkyard ECU is just fine though.

Now, I assumed your issues were IACV + ECU due to that $1800 dealer quote, not many other things that would make sense at such a price. Speaking of which, did you get the error codes from the dealership or is there any codes at all??

Finally, you can test the IACV indeed. Get a multimeter and look at this link (you will need Pg. 432)

http://www.nicoclub.com/FSM/Maxima/2001/EC.pdf

Monty51

Thanks, that's a good link. I can get the engine codes from an $89 auto store code reader (hope that's good enough) and I'm familiar enough with a VOM to check out the IACV.

I'll take a look at this info and post back what's up when I get a chance, but it probably won't be for a couple of days...I'm busy cleaning up water damage from recent flooding.

D.Stillwell

No prob dude, happy to help.

Btw, did you know that you can get the codes read for free at any Autozone? Something to keep in mind, if you don't want to buy the scanner. However, having a scanner will 100% come in handy.

Good luck with the water damage and do report back to us on this, it's always nice when these threads have a conclusion so other people can get good info from them in the future.

WTF?

This thread isn't concluded is it????? By the way, pull a vacuum line is good advice. You seem to not know how things work. Better yet, route a vac line around the throttle body and see would work even better. Go Google some ****, and learn why.

D.Stillwell

What? Is this a joke

LOL OK

I know how it works, if you pull a vacuum line you then have an air leak you re-tard. And you didn't even mention which vacuum line. At this point, I would ask you to please STOP giving out BAD advice to people.

WTF?

LOL.....do you know what a PCV system is? A vac leak AROUND the throttle body, just goes through the engine. It is a controlled leak, why do you think a bad PCV valve causes a car to run rough, or not idle? The IAC valve is a freaking hole that bypasses the throttle blade, same as a vac line routed AROUND the throttle body. Learn something yet? Now, if car doesn't idle, and you pull a line and it idles, then the pcv valve is suspect, if it still don't idle, then you plug the PCV line and see if it idles. It's called trouble shooting. Very very basic mechanical troubleshooting. Your advice is sound, but you are just basically telling him to go buy parts without checking anything at all. Not smart, and could get expensive.


Why would it matter what vacuum line? They are all hooked to the same engine, aren't they? Any vacuum line between the intake valve, and the throttle body will do.

99zx2

iTrader: (3)

^ why would it idle better with the line pulled? unless it's not getting the air it needs.

OP, is the car throwing a cel yet? i'm troubleshooting my own max right now that has a similar issue. double-check your intake piping and make sure it's solid. Pull the maf plug and see if anything changes. Clean both the maf and tb, then check again. Report back.

Child_uv_KoRn

iTrader: (7)

Yes, obviously, the IACV is stuck closed. So, it's not going to idle. Pulling a hose will let it breathe and then it magically runs.

Are we also going to learn how to read time, today? JFC

D.Stillwell

Whatever you guys say ^^^

WTF dude, I just replaced my PCV valve. You really gonna give lessons on PCV valve?

(I know how it works )

I NEVER told the OP to throw parts at it, I gave him his most likely scenarios based on the info he provided and told him to get the codes, come back and tell us what it is. I don't give out crap advice, I take this seriously because this site has helped me hundreds of times over the years.

I also gave OP link to the FSM, and the proper way to test the IACV, so he can rule that out. Never told him to throw parts at it.

That said, we still don't know what the actual problem with OP's car is, he has to update us on that. OP was stalling while driving and letting off the gas, might not even be the IACV and just a dirty TB.

Anyway, yes pulling a vac line can be useful for diagnosis, I never argued that point. I just said that in this case, it's pointless because it's not gonna tell the OP anything he already doesn't know or suspect of the problem. Doing the IACV test from the FSM is way more useful, sorry. Creating an air leak so the car can run like ****, when you already know you have a problem somewhere around the TB is useless. Oh and not everybody knows that you can pull any vac hose between intake & TB, would be useful to mention that if you tell someone to pull hoses.

Pariswagg

I have a 2000 maxima with a p0505 code iac now car won't start can iac make car not start

Pariswagg

I have a 2000 maxima wit a iac code car was starting now it won't start can iac make car not start

maxiiiboy

Yes, a bad IACV can prevent the car from starting. And the dreaded P0505 indicates there might be a serious problem.

Read the post above by d. Stillwell, and then this note: https://drive.google.com/file/d/0B6O...psNVBqUVk/view ; it describes the "IACV problem and the solution options you have.
This thread https://maxima.org/forums/5th-genera...d-seconds.html contains basically the same information, just not as well organized.