I know this has been addressed many times here before but I wanted to make a new post that addressed all of these problems as a result of a single part rather then many different malfunctioning parts. All of these problems can be caused by lots of different things BUT, there is one thing in particular that can cause all of these problems by itself. The part is the Idle Air Control Valve (IACV).

Basically, over time carbon deposits can build up on the valve and cause it to stick. If it sticks, it can cause the TPS sensor to not work properly which can cause the snowball effect to begin (leading to more and more problems). Here are the following problems I had and my diagnosis of them (you'll begin to see the "snowball" effect this little b@stard valve can cause!):

-Lopy idle (a result of misfiring)
-Running extremely rich in low-end and at idle (real-time diag on ECU)
-Running lean in the top-end and throughout most of the rpm band (real-time diag on ECU)
-Misfiring (a result of running so rich at idle/low-rpm)
-Missing/bogging low-end (running too rich will bogg the engine down)
-Missing/bogging high-end (running lean can have the same effect as running too rich)

I've been having ALL of the afformentioned problems. Basically, my whole entire power band seemed to be lacking. It all boiled down to the IACV. My IACV was clogged with carbon deposits, which in turn caused the valve to stick. Because the valve was stuck, this can cause air to be entering through it when it is not supposed to. A direct result of this is that the TPS sensor will not function properly, and replacing/adjusting the TPS will have no effect. With the valve stuck, a direct result is also to cause the engine to run rich with the throttle closed and low-rpm, as well as running lean through most of the powerband. Running so rich and lean at the same time can also cause your Maxima to misfire a lot and have a lopy idle. With the TPS not functioning properly the throttle doesn't quite act right in that it takes awhile for the rpm to fall. This can be seen in engine braking, revving with the clutch pedal in or in neutral, etc. Basically, after 2yrs of diagnosing these d@mn ECCS gremlins I found out MY problem. All I did to fix all of my problems was remove the IACV and spray carb cleaner through it to clean all of the deposits off. After 2yrs of replacing parts and dealing with this crap, I solved my problem in 5min (the parts I replaced helped of course)! One thing I should state is that out of all the parts I replaced, none of them really had much of any effect on the problems I was having. Cleaning the IACV is the only thing that has drastically changed/eliminated these problems. So far, everything is working great but I haven't put any serious mileage on my car since fixing this. I'm going to fill up with gas today and see how my mileage will be affected. I'll respond later next week to let people know if cleaning the IACV really has helped me that much with performance, gas mileage, etc. I replaced the following trying to fix all this crap:

-spark plugs
-wires
-dist cap
-rotor
-air filter
-fuel filter
-pcv valve
-ignition coil
-MAF
-cat
-o2 sensor
-tps sensor


Now, this IACV valve is really tricky because I have seen lots of other posts where people with similar problems have replaced the TPS, EGR, FPR, etc and it doesn't help plus the problems continue. Let me tell you this, CHECK THE IACV!!! I never thought that simple little valve could cause all the problems I was having but the fact is, it was pretty much the single reason I was having ALL of those problems! There are, of course, many other things that can cause these problems. So, cleaning the IACV might not work for everyone but, it is definitely something you should at least try.

 

I hate to sound like an idiot, but where is the idle intake control valve? Do you have a photo? I would imagine mine needs a good cleaning, too.

thanks

 

Idle Air Control Valve (you know what I meant)

 

You have a VE so I'm not quite sure.

 

If the search is running you can look up some old threads where I explain an easy method to clean the IACV for the VE.

 

Shadow, do you have AIM? IF you do, IM me at KLoWnPR109

 

Where is this located on a 1990 maxima GXE ?
The millage on my car is very low. It is averging at 100 miles per tank on city. (Queens NYC) and 180 miles per tank on highway. This is from traveling back and forth from StonyBrook.
The pull from my car is ver slow and the car feels heavy.

Can this be a problem from the nasty IACV. Oh please let it be this problem. I never saw my car leak gas and this hungry car is making me broke.

 

Also, the car is sounding old. I hope you guys know what i mean by a old car noise. But it is mainly coming from the right side. Can this be caused my the timing belt?

 

As Eric mentioned, refer to this thread: http://forums.maxima.org/showthread....threadid=99296

 

thanks, I am going to try that tonight after work.

 

what about me? What should i do?

 

Pkny514, the IACV is located on the side of the intake manifold. It is a square box shaped object. It has a vacuum hose connected to it that goes to the black "s" shaped intake piping. It has 4 6mm hex head bolts holding it in place. There are also some other vacuum hoses that you might have to remove, that are in the way. On top of that there is one coolant line on the side of the IACV that you'll probably want to take off to get the IACV valve off. Basically, with the valve off just spray LOTS of carb cleaner through there and then put it back on. With older Nissans in general, it sounds like these valves are kind of a big pain in the butt! Many of my friends with 240sx's (some with sr20 swaps) are having similar problems to what I was having, and they sound like it could be the idle control valve on their cars as well.

Pkny514, have you done all the regulard maintenance stuff. If not, I'd take care of all that as well and it should help improve your mileage. Here's a list of some of the basic stuff to replace:

-spark plugs (use NGK's)
-plug wires
-distributor cap
-rotor
-ignition coil
-o2 sensor
-fuel filter
-air filter

Can't think of anything else.

Klownpr109, I don't have AIM (damn firewalls!) but my email is fred.brown@amd.com Just email me and let me know what's up. BTW, I'm in Austin, I see you are in Longview.