Jump to content



Photo

I am stumped at this one......2001 Maxima VQ30DE


  • Please log in to reply
4 replies to this topic

#1 Beard

 
Beard

    Advanced Member

  • Members
  • 52 posts
  • Gender:Male
  • Location:Charleston, South Carolina
  • Interests:Surfing, bicycling and motorcycle building
 

Posted 01 February 2010 - 08:38 AM

Alright, I ma having a bit of an issue trying to figure out what the problem is with this car. It is throwing a IACV circut fault code. Another shop installed a new TPS, new IACV and they said it needed a new cluster so they installed one of those as well. Well, I went through and checked the stuff they did and found that they set the TPS at .88v, which is way over spec. Facotry specification is .45-.60v at closed throttle. I set the TPS to correct specs and the problem still persists. I searched Alldata for TSB's regarding this issue and I found one that says the fix is to reprogram the PCM with an updated program. I tried to reprogram the PCM with the new program and the program wouldn't take with my programmer......so I took it up to my buddy at the dealer and they couldn't get it to take. So far this is what I know, IACV % at idle is supposed to be @ 15-25% and it is hovering around 45% at idle sometimes working its way down to 30%. When commanded to 100% (100 steps) the idle does not change at all. I have checked for vaccuum leaks, found none. I have checked that the throttle plate is 100% closed, it is. I made sure factory idle mixture screw is where it is supposed to be, it is. Now, I am at the point where some other heads on this problem could be helpful. PCM won't take a program, wont communicate with new IACV and when started cold, it will not want to idle on its own for the first 5-10 seconds of engine run. After the vehicle has warmed up, it runs and starts perfect. I will send a Wal-Mart gift card to anybody that can explain this problem and help me find a fix. I am serious. Thanks fellas, Daniel Beard Auto Care Express Mount Pleasant, SC (843)884-9700

CRIME CONTROL, NOT GUN CONTROL!!

Any Duramax diesel questions? Ask me I may have an answer

ASE Master

GM / Duramax Master

Associates in Business Management

Associates in Advanced Automotive Technology


#2 Beard

 
Beard

    Advanced Member

  • Members
  • 52 posts
  • Gender:Male
  • Location:Charleston, South Carolina
  • Interests:Surfing, bicycling and motorcycle building
 

Posted 01 February 2010 - 08:45 AM

Oh yeah, forgot to add.....I tried doing an Idle Learn on the car and the learn failed every time I tried.

CRIME CONTROL, NOT GUN CONTROL!!

Any Duramax diesel questions? Ask me I may have an answer

ASE Master

GM / Duramax Master

Associates in Business Management

Associates in Advanced Automotive Technology


#3 austintech

 
austintech

    Member

  • Members
  • 18 posts
  • Gender:Male
  • Location:Forney, Tx
 

Posted 02 February 2010 - 08:57 PM

one problem I have seen while working at Nissan was the harness like to break around the the back of the strut towers where the harness goes into the firewall, when this happecs you might want to check the pcm.

#4 nismaster

 
nismaster

    Newbie

  • Members
  • 2 posts
  • Gender:Male
  • Location:poughkeepsie ny
  • Interests:mtorcycling
 

Posted 02 February 2010 - 09:58 PM

i got two possibilities for your issue. first, do you have the original iac valve? reason being that sometimes they short out and wipe out the ecm. easiest way to check is to measure resistance between both upper and lower rows. place one lead on the middle pin and measure resistance on on pins to the left and right, and do the same for the other row. 0 ohms and you will most likely have a bad ecm. if you replace unit, note that car will not start until keys are programmed and idle relearn needs to be done. second possibility is going to be an airflow meter issue. you need to look at your fuel trims, too high or low will most likely require replacement of sensor and ecm reprogram (assuming the use of facory replacent parts). based on your post, i'm biased towards first possibility.

#5 nismaster

 
nismaster

    Newbie

  • Members
  • 2 posts
  • Gender:Male
  • Location:poughkeepsie ny
  • Interests:mtorcycling
 

Posted 02 February 2010 - 10:13 PM

Alright, I ma having a bit of an issue trying to figure out what the problem is with this car. It is throwing a IACV circut fault code. Another shop installed a new TPS, new IACV and they said it needed a new cluster so they installed one of those as well. Well, I went through and checked the stuff they did and found that they set the TPS at .88v, which is way over spec. Facotry specification is .45-.60v at closed throttle. I set the TPS to correct specs and the problem still persists.

I searched Alldata for TSB's regarding this issue and I found one that says the fix is to reprogram the PCM with an updated program. I tried to reprogram the PCM with the new program and the program wouldn't take with my programmer......so I took it up to my buddy at the dealer and they couldn't get it to take.

So far this is what I know, IACV % at idle is supposed to be @ 15-25% and it is hovering around 45% at idle sometimes working its way down to 30%. When commanded to 100% (100 steps) the idle does not change at all.

I have checked for vaccuum leaks, found none.
I have checked that the throttle plate is 100% closed, it is.
I made sure factory idle mixture screw is where it is supposed to be, it is.

Now, I am at the point where some other heads on this problem could be helpful. PCM won't take a program, wont communicate with new IACV and when started cold, it will not want to idle on its own for the first 5-10 seconds of engine run. After the vehicle has warmed up, it runs and starts perfect.

I will send a Wal-Mart gift card to anybody that can explain this problem and help me find a fix.

I am serious.

Thanks fellas,
Daniel Beard
Auto Care Express
Mount Pleasant, SC
(843)884-9700




1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users