UPDATE: It idled high after driving it today. Around 1800 to 2000 rpms at times. Also, the cruise control slows down, so there's probably a vacuum leak causing this.

2001 Maxima, 161k, manual
It won't hold idle when you first turn it on when it's cold. After giving it gas for a moment, it barely holds idle around 400-500 rpms. When it's warmed up, it idles at about 750 rpms. I think there could be a vacuum leak since the cruise control loses speed periodically.

It has codes that say the o2 sensors are all shot, as well as the knock sensor. The throttle body (which has the IAC valve on it, if I'm understanding it correctly) looks new, but I bought another just in case (hasn't arrived yet).

Any ideas what might be causing this?

Thanks.

- Brian

 

Your codes are telling you what the issue is. You need to start there by searching for theads on this forum, there are plenty. Determine if you have fed or cali spec. My guess is cali since it's an 01 but the label on the underside of your hood will tell you for sure. The codes for the O2 sensors will specify a particular one primary/Secondary & bank 1/bank 2. Knock sensor isn't the easiest to replace but with right tools it can be done. Again plenty if threads on that too. Good luck.

 

Bad O2 sensors can certainly cause a wonky idle.

 

o2 sensers all out??
The fuse under the dash might be blown. it's 15a.

 

Ok, I'll check the fuses before I change the o2 sensors. Not sure if it's cali or fed. Didn't think it would be cali since I'm in Texas, but I don't know much about these cars.

Also, the cruise control slows down sometimes, so I'm guessing there's a vacuum leak that's messing with the idle as well.

Thanks for the input.

 

If the fuse blows, does that cause the codes to come up as o2 sensors going bad when all i really need to do is change the fuse?

 

Since the idle varies and my cruise control speed slows sometimes, I'm guessing a vacuum leak is the main cause. But I think the o2 sensors could be messing with it too.

 

You may need a new iacv or if yours was just replaced it may be a cheap unit. I replaced mine with a $40 eBay one and every now and then when I start the car after driving a bit it will cut back off before it can idle. It only happens when its warm. A blip of the gas right after starting and the problem always went away. When my iacv broke I was idleing at 1500-2000 rpm and it was literaly gulping coolant through the seal in the iacv. A gallon every 4 days too be specific. No real advice can be offered unless you go to AutoZone or advanced and have them tell you what codes you have.

 

Yeah, I just got the IACV in the mail a few days ago from eBay--probably the same one you got. lol Cost me $35 I think. I'll probably change some vacuum hoses and the IACV when I replace the valve cover seals and knock sensor.

I already know what codes I have. Knock sensor and all three o2 sensor codes.

Thanks for the advice. Much appreciated.

 

when you do iacv bypass the coolant- and if you think the iacv is bad might as well pull the ecm to check for damage

 

Why would I pull the ECM just because I'm doing the IACV? Is it by the IACV? I'm confused. (I obviously don't know much about these cars)

To bypass the coolant, will I just need to put a hose going around the IACV or throttle body? That's what I've always done to my Taurus SHOs.

- Brian

 

https://maxima.org/forums/5th-genera...d-seconds.html

iacv going can take out the ecm in these cars. lots of members have had to send it off for repair to solve their issues. long story short, it's suspected the iacv gasket fails, coolant leaks in, shorts the iacv and take out the ecm with it. hence the reason for the coolant bypass- basically you want to do what you said, route the coolant out of the iacv, i had to buy generic hoses to do this, but i think some members have reported being able to reuse the old ones

maxiiiboy has been consolidating info on this issue, perhaps he will post a link to his most recent document on it

 

Here: https://drive.google.com/file/d/0B6O...hibHlkRmc/view (URL updated 7/20/16)
Cephyr, read the above document before doing any repairs .

 

Will do. Thanks so much.

 

Thanks for the article. I'll get those issues taken care if while I'm replacing the IACV.