JAmerican

I brought my 1996 Stock Engine/Manual Trans. Nissan Maxima SE to a repair shop to have valve cover gaskets replaced back in January. Recently, I got a leak from the rear valve cover and got the valve cover gasket replaced once again, free of charge (since it's within a year). Now, I'm experiencing high idle situations. I told the repair shop and they told me after having the car for a couple of hours that they replaced a tube.

I'm still experiencing high idle though but it's not as soon as I turn on the car, it happens like 35+ minutes after driving my car that my idle will go from ~700RPMs to ~1500RPMs in neutral. When I stop and shut off the car and turn it back on, my idle immediately goes back to ~700 RPMs. I'm wondering if this could be a computer issue because this happens like clockwork.

Will resetting the ECU help? BTW, I got the rear valve cover gasket work done on Wednesday of last week and I've used carburetor cleaner to try and find a potential vacuum leak to no avail. I also had two codes on my car after they did the repair:

Code: P1105 | Description: Manifold Absolute Pressure Switch


Code: P0174 | Description: Fuel Injection System: Left bank lean


I was able to clear both codes and have not seen them since. Any suggestions?

DennisMik

iTrader: (2)

They may have either left a vacuum hose disconnected or mixed up reconnecting some of the hoses. If they mixed up connections, that will be difficult to figure out without another car to look at. If they left one off, that is also difficult as you need to know where a hose is supposed to be.

IACV (Idle Air Control Valve) has 4 hoses on it and they probably had those disconnected. The MAP/BARO Switch Solenoid is by the front valve cover, but you don't need to mess with it for a valve cover replacement.

All I can suggest is to start looking around the engine on the driver's side and see if you can find a disconnected vacuum hose..

ShocknAwe

iTrader: (3)

WHen looking for a disconnected hose keep in mine there is a breather hose coming from the transmission that isn't supposed to be connected to anything. The open end should be located where the top radiator hose connects to hard line at the water temp sensors

maxed_out_99

i would check the throttle cable and make sure its not binding causing the throttle to be stuck open

i agree with the vacuum line issue as well

Fr33way™

iTrader: (23)

I would check the throttle body coolant line, it is definitely a pain in the *** the first time around and if they did it more than once they may have capped it to shortcut. If the idle is not reset correctly the high idle cam (cold start) can kick on randomly.

It doesn't relate to either one of those codes but I would check that line. It passes through the throttle body on the bottom.

Rob_0126

Whats the exact timing and condition of when the idle goes up?

Like how many minutes, seconds til it goes up and whats the temperature of the engine(if that comes into play)

Im hardpressed to believe its a vacuum line unless its hooked into a vacuum switch because its not all the time.

JAmerican

Here are some screenshots I took from my phone using OBD DroidScan Pro for Android. This hopefully will explain what I'm talking about...

This is what the beginning of my trip looks like. When cold, I feel acceleration drag initially then it feels normal. My car also goes to 1000 RPMs when first in neutral then down to ~700RPMs.



This is until I've driven for more than half an hour and the following results. I don't know exactly when it occurs because it's only detectable when the car is in neutral.

CMax03

iTrader: (3)

air intake leak more than likely or a vacuum hose not connected.....You resecured your EGR valve?

JAmerican

I don't know if it could be an air intake leak or vacuum hose leak because it is almost clockwork that my RPMs double around half an hour. I drove to work (~22 minute commute) and didn't see any RPM doubling when I parked in neutral. This has to be something that is more controlled like a electrically-controlled valve related to the throttle or the computer I think. BTW, when the RPMs double, I don't see a change in the throttle switch next to the cruise control switch that has metal wires connected to them. If it was a leak, then the change wouldn't occur around the same time all the time, or am I wrong?

njmaxseltd

iTrader: (19)

Why is the timing at 33 degrees at idle and only showing 5 or 15 at first?

CMax03

iTrader: (3)

maybe your IACV went south and is bad or leaking air...

JAmerican

I'm assuming that's related to the RPM doubling as that value doubles when the RPM doubles. Not sure exactly what that means though

JAmerican

What's interesting is when I disconnect my IACV, my throttle drops to like 500 RPMs then returns to ~700RPMs. When I start the car without the IACV, my RPMs go as high as 2000RPMs then returns to around 700RPMs. I also DO NOT get a code when the IACV is disconnected. Is that normal?

JAmerican

Sorry, I made a mistake. I disconnected my Throttle Position Sensor and my RPMs dropped not my IACV.

JAmerican

Hey all,

I've fixed my issue. The real asinine thing to do is to leave it at that but I believe in giving back to the forum that has helped me so much so here goes!

After bringing the car back to the mechanic's shop twice after they replaced my Rear Value Cover Gasket, they told me they could not find a leak. It was only when I was browsing through the forums for similar symptoms:

• High Idle @ 2000 RPMs when cold
• High Idle @ 1500 when warm
• Idle drops to ~700 RPMs then back up to ~1500-2000 after 30 min
• TPS replacement didn't solve issue
• IACV ticking
• and more symptoms

I found these threads...

http://forums.maxima.org/4th-generat...need-help.html

http://forums.maxima.org/4th-generat...g-dummies.html

They were the best resources in solving this problem. I found that my car had significant carbon buildup in the intake manifold (IM), Throttle Body (TB), Idle Air Control Valve (IACV). I did not attempt to remove and clean the EGR as I could not get a gasket to replace the lower EGR gasket. I also didn't have problems related to the EGR. These are the results of before and after cleaning the TB, IACV, and IM.

***BEFORE***







***AFTER***




Extra Cleaning occurred after this picture to get rid of black spots!

JAmerican

Here's are the gaskets that were replaced...



The next part of the fix consists of disabling the Fast Idle Cam & Plunger! This was the actual cause of the high idle situation on my car. After cleaning the TB, IACV, and IM, the car was consistently at 1500 RPM when warming up and 1000 RPM when warm. This and with the help of the reference posts above told me that I had a throttle-related issue. The IACV was ticking and the IACV screw was completely in. When I took the throttle off again, I inspected it and found this....

***BEFORE***



Fast Idle Plunger on Left; Fast Idle Cam on Right



***AFTER***


Adjust this screw and nut (left picture) such that the Throttle Pulley Assy sits on this factory set point in the right picture (DO NOT ADJUST THIS POINT!!!)

Space exists between Fast Idle Cam and Throttle! This disables it from functioning!


Some space still exists in the Throttle body

After reconnecting everything except the TPS, my car would rev high to 2000 then drop instantly down and stall. This told me I had no vacuum leaks (when cold). I unscrewed the Idle Screw just enough to allow air flow. I turned the car on and let it warm up so that I could adjust the resistance of the TPS to 500Ω closed and 3.6kΩ WOT. This TPS adjustment may not be necessary if you did not remove or replace your TPS but it doesn't hurt to check the TPS for proper resistance values when your engine is at operating temperature. I then set the idle RPM to 600 (575±50 RPM). Then I connected the Brown cable to the TPS to set the proper TPS configuration in the ECM. I turned off the car and turned it back on to see the car rev to 1500 RPM then drop down to ~620. I adjusted the screw to 650 (625±50 RPM). The reason I set my values a little above the recommended values is because I want my car to run on the higher end of the spec because I have to tighten the idle screw to reach their values. I also want my car to be able to run a little faster to get it to warm up quicker. The IACV ticking is non-existent now. My car used to hesitate when pressing and releasing the gas and this is no longer a problem as well.

Something I noticed other people did was apply a coolant bypass mod. I did not attempt this because I live in NY where its cold 8-9 months out of the year usually. I did not want my Throttle Body to freeze. Also, if the Cam actuates, it will move further from the throttle, not closer to it.

All in all! I'm happy and Maxi is happy!

99maxwell

iTrader: (1)

ok so i think that you solved an issue ive had since i bought my car almost a year ago. I have been having this high idling thing going on since ive owned my maxima and its really aggravating. my car has 125,000 miles on it and i never got around to cleaning my TB and IACV so im assuming my carbon build up is quite bad. also i have the code come on and off constantly for egr so im assuming its really badly built up with carbon and im going to take care of that on thursday. but i need to know if you could give me a walk through on how to fix the high idle by any chance? cuz i got a little confused with your pics and i REALLY want to get this issue fixed
also was it easy? because im not mechanicaly inclined and im taking a big enough risk as it is cleaning all that carbon build up on IACV and tb and egr. also where can i get the gasgets for the IACV and egr tube? any help would be apreacieted! thanks

kroze

Yea i'm kinda confused looking at the pics too.

JAmerican

Sorry, I posted that right after fixing my issue. I was super excited and thought it would be obvious. I am going to re-do the post tomorrow. I need to go to sleep now for work tomorrow. Come back tomorrow and I'll explain it better. As for how this could be the problem, I posted in your thread an pretty good explanation I think...

http://forums.maxima.org/8646163-post19.html

kroze

Here I fixed it for you! Thanks again, this fixes my car idling problem @ 1700rpm.

maxx0831

iTrader: (2)

I had this problem when I had my 4th gen. When I had both valve cover gaskets changed, I had a high idle on warm starts when the engine was already warmed up. My fix was because the egr valve gasket wasnt changed and wasnt tighten down as much either. Had to take apart everything and changed the egr valve gasket and after that, no problems. And also the air intake gasket.

kroze

Of course, it's never a 1 solution answer for any car problem.

But this is cheap and easy to figure out.

JAmerican

WOW! That was simple! I tend to explain more than I need to lol. Just to be clear to everyone, doing this will disable the Fast Idle Cam. This means the car may take longer to warm up in the morning but from my experience, the car seems to Fast Idle in the morning when cold and drop to the correct level when up to operating temperature. This may be due to a resistance change seen at the TPS sensor due to the cold Throttle Body reflects a different resistance at the TPS then a warm Throttle Body.

JAmerican

I recommend that if you haven't done simple repairs on your car that you do not attempt larger repairs like this one where removing the throttle body is recommended. You could go through the process of removing the air box and intake air tubing up to the throttle body. This will give you the clearance needed to modify the screw in the second picture...



You need to first confirm that this is your problem by looking at the place on your throttle body circled in the first picture.

99maxwell

iTrader: (1)

alright thanks man i appreciate it! also i took a look at it this morning before i went to work and yes, that gap is there so that's my problem. And if I feel up to it after getting everything else off I may decide to remove the whole TB assembely because I deff want to get it off so i can get a good cleaning on things. I was planning on doing everything tmrw but I don't have the gaskets for the TB or IACV so I was wondering where do I buy the gaskets because I have 2 days off next week and I want to get this done asap before it gets too cold!

JAmerican

Good point. BTW, there should be a gap when the coolant is cool. When your car is at operating temperature, the gap should not exist. Do you have tools already? If not, I recommend Sears Craftsman. Lifetime Warranty . As for the Cleaning, I recommend you look over this...

http://forums.maxima.org/4th-generat...g-dummies.html

I recommend gaskets from the dealership. Check out your local dealership's website. They may have an option to pickup parts that are ordered online. You may also get a discount by ordering it online. The link above tells you the Part# for the Throttle Body and IACV Gasket if you are going to remove both. If you do clean the entrance to the Intake Manifold...



Be careful with the EGR shown in the back of the Intake Entrance. I recommend you block it temporarily so that Air Intake Cleaner doesn't drain into it (if you are not removing the EGR). Lastly, make sure to follow the Factory Service Manual and that you get a good 3/8" torque wrench so that you don't over-tighten or under-tighten your Throttle Body or other sensitive components.

99maxwell

iTrader: (1)

Alright man just order'd some gaskets from a local dealer! and I'm not sure I'm gonna do my EGR i want too but it looks like a PITA to do so I'm undecided on that still and I looked at that thread on how to clean everything so I think I'm all set to get started once I get the gaskets. Thanks man for all your help I really appreciate it!

JAmerican

No problem. Glad I could be of assistance. Also, I didn't remove my EGR, because I also thought it would be a PITA and I couldn't get both gaskets for it. Also, my car never gave my any errors or problems related to the EGR so why touch it . My car feels like new after this and has a lot more energy . Good luck.