matty

iTrader: (54)

After my 96 se with 87K on it warms up i have a problem when i stop(5spd)...the first time i hit the breaks the idle goes down to about 400rpm's...i dont know if this i normal and it only does it once almost every time i stop but ONLY once ?? then after i slow up more it goes back up to normal 650 rpm's at like a light... jsut wondering if this is normal...thanks

Daniel B. Martin

It is not normal.

Here is some text copied from the factory service manual.

"Idle Air Control Valve (IACV) -- Auxiliary Air Control (AAC) Valve

This system automatically controls engine idle speed to a specified level.
Idle speed is controlled through fine adjustment of the amount of air which
by-passes the throttle valve via the IACV-AAC valve. The IACV-AAC valve
changes the opening of the air by-pass passage to control the amount of
auxiliary air. ... "

You may make a quick test of your IACV-AAC in the following way. With the
motor at normal operating temperature, and at idle, switch the A/C from
"off" to "maximum". Keep your eye on the tachometer as you do this. The
idle speed should dip momentarily and then recover. If it does this, the
IACV-AAC is working. If the idle drops and does not recover, the engine
may stumble, falter, and stall. The IACV-AAC may require cleaning,
adjustment, or replacement.

The correct idle speed is...
- 700 +/- 50 (automatic transmission, in Neutral)
- 625 +/- 50 (5-speed)

There are other engine parts which play a role in maintaining the right idle
speed, but the IACV-AAC is the first thing to look at.

jmwells00

you could have a blow fuel pump regulator... it is very rare but it happens when you run really hard when the engine is still cold... my truck had that happen to it and it costed me $300... hope for the best!

matty

iTrader: (54)

I did that to the T and it came out like completely oposite...i turned on the A/C to max with everything else off and at regular tempurature....it went up to about 900rpm's without any hesitation then when i turned it off about a minute later it fell below idle and fumbled alittle BUT NOT BAD.. it was far from stalling but just a little fumble..oposite of what you said ?? what do ya think...

Daniel B. Martin

I think your IACV-AAC valve is working, but imperfectly. It overshoots when adjusting the idle. Perhaps it can be restored by disassembly and cleaning.

matty

iTrader: (54)

do you think you can point me out where this is or you can just tell me to "buy a nissan repair book you lasy a** "
take your pick ----thanks

Daniel B. Martin

I'll do both.

I urge all Maxima owners to invest in an aftermarket repair manual, Chilton or Haynes. Haynes is the better of the two. Even if you don't do your own repairs, a quick read of the manual can help you deal with a professional service provider. In blunt language, it will help you to avoid a rip-off.

The Idle Air Control Valve - Auxiliary Air Control valve is fastened to the rear side of the upper intake manifold, immediately downstream of the throttle body. Connected to it are one large black rubber air tube and one electrical connector. It is just a couple of inches away from the Cruise Control actuator, though the two parts are not connected in any way.

95greense

daniel, doesn't the valve have two hoses? i have a 95 and it looks like it has two hoses. just makin sure cause i just took mine off and i want to make sure that i have the right part. i'm going to try to clean it because my dealer is charging $175 for the part. ouch.
also i was wondering if there was anything i should be looking for or anything special i should be doing while cleaning it or is a simple open it up and clean? thanks in advance for your help daniel.

Daniel B. Martin

As far as I can see, the IACV-AAC valve has only one hose... but I am looking at my '99 Maxima. Your '95 might be different. The hose is about as thick as your thumb and connects the intake air duct (just downstream of the Mass Air Flow Sensor) to the IACV-AAC valve. Do not confuse this part with the EVAP Canister Purge Volume Control Solenoid Valve which is in the same general neighborhood and which has two hoses.

Maybe you need a manual to guide you... but I've said that before.

I hesitate to say how difficult the cleaning job might be. I have successfully cleaned and rejuvenated this valve on older Nissans but those valves were simpler, being operated by a solenoid rather than a step motor. If it was my car I would attempt to clean the valve. I won't part with $175 without putting up a fight first!

95greense

you're absolutely correct daniel. thanks for saving me the time of taking apart my canister purge thingy. anyways, after cleaning the IACV valve to operating room standards my car still has the problem. so i'm thinking that either my IACV is totally shot or i'm fixing the wrong thing.

sorry to keep asking you daniel but i just want to make sure that i'm fixing the right thing. my car runs completely smooth after 1K rpm. but when i'm at idle with the engine warm the idle is at 600 rpm and dips to almost stalling then goes back to 600 rpm again. it actually stalls sometimes. while idling at 600 rpm the car doesn't just have a rough idle it bucks. i'd almost say that it feels like one of the cylinders isn't firing. when driving or on the freeway the car drives like a dream as always and idle is the only time i have problems. turning the steering wheel or turning the air on will cause a slight bump in the rpms but never past 600 rpms.

i know that from your previous posts that roughly 700 rpm is normal for auto maxs and it's not just a low idle anymore. does this slight bucking signify a different problem? should i just give up and bring it into a shop? thanks for your help daniel.

forgot to add that the only error code that i get is for rear heated o2 sensor. i've known about that one for awhile but figured i could wait on that repair. do you think that is causing this?

Daniel B. Martin

Matty originated this thread with a symptom report of low idle speed when the car came to a halt. I responded to him with a pointer to the IACV-AAC valve. Then you jumped in (and that's okay) with the same symptoms... or so I thought. It turns out your symptoms are not the same as Matty's. Figure out what your symtoms are and start a new thread. We'll go from there.

emax02

iTrader: (1)

My Rpm's plumit down to 300ish Rpm's. It only happens when I put my car in nuetral when I am moving,it quickly corrects in self. My check engine light is on too,but I have not checked to see what the error code is yet. Anyways I found a cure for the problem {kind of}, I just click my winshield defroster on my auto climate control. When I do this my Rpm's stay at about 1100 rpm when the car is in nuetral. P.S. I will fix the problem one of these days.