Idle problem

[dickiesmalls]

Here is my issue or how it started and where I am at now. I have a 2000 nissan maxima se. It began to stall at red lights or at idle. This was very intermittent but once it started to act up it would do it consistently during the drive. I had a guy try and do and idle air relearn and it wouldn't complete. He said it was the iac. So i replaced it with a standard motor products after market one and it still wouldn't do a relearn. I then replaced the tps and tired a relearn with no luck. I put the old one back on. I then cleaned the mass air flow sensor and throttle body value, replaced the spark plugs and coils(after market) and it finally did a relearn after about 15 attempts. After doing a relearn it idled fine for a few hours then started back having issues. Now, not only does it have idle issues I am getting about 18 mpg. It also will do like an idle surge where the rpms will jump while it is shifting between gears but is very intermittent. If I hold the rpms at 1500 it will jump or bob up and down. If I rev it up to about 2500 rpms and let it drop it will try to catch it self to idle but it either stalls or catches it self at like 200 rpms. I decided to take it to a dealer and they said I had a bad mass air flow sensor, a bad rear heated 02 sensor and a bad engine control harness. Total of about $3000. The codes I have are P1320, P0139, P0138. I never saw the P0505 code. I have read a lot here where people have had to replace the ecm because of the iac, but the dealer said they tested the ecm and it was fine. I need some help. Could an after market iac cause all of this? Could it be the mass air flow and o2 sensors? Below is the data monitor info I got from the dealer.

Eng Speed 0 rpm
MAS A/F SE-B1 1.32v
A/f ALPHA-B1 100%
A/f ALPHA-B2 100%
HO2S1 (B1) 0.00v
HO2S1 (B2) 0.00v
HO2S2 (B1) 0.29v
H02S1 MNTR(B1) LEAN
H02S1 MNTR(B2) LEAN

[maxhopper]

The only things listed that would cause the issue are the MAF or the harness. Did they tell you what they thought was wrong with the harness?

I would personlly lean towards the MAF or possibly a vacuum leak.

[dickiesmalls]

The just said a short in the wiring harness then went on about the bulletin NTB02-051a. They couldn't give me any specifics. I talked to another guy that works there (a family member of one of my friends) and he said they just really didnt want to take the time to track it down. If I replace the MAF do I need to do an idle air relearn? Is it ok to use an after market iac?

[maxhopper]

I would install the new MAF and see how it ran before doing the idle relearn. Just disconnect the negative battery cable for at least 5 mins while changing the MAF.

Nothing wrong with an aftermarket IAC as long as it didn't come from autozone (I just don't trust their electronic parts).

[dickiesmalls]

Thank you for your help. I will let you know how it turns out.

[dickiesmalls]

Hey Max, I was doing some research and there is a service bulletin 01-036A that has to do with the MAF code P0100. It says to update the ecm after installing a new one. I don't have that code, should I worry about getting the ecm updated once i put the new one on?

[maxhopper]

I wouldn't worry about it since you don't have that specific code.

[korner]

I would install the new MAF and see how it ran before doing the idle relearn. Just disconnect the negative battery cable for at least 5 mins while changing the MAF.

Nothing wrong with an aftermarket IAC as long as it didn't come from autozone (I just don't trust their electronic parts).

Why the disconnecting of the battery? Is that to get the LTFT reset to Zero?

[NutriaforBreakfast]

I am leaning toward the vacuum leak
You might call around and try to find someone who has a smoke machine
The smoke goes into the intake of the throttle body using air compressor power and you can find leaks sometimes

[NutriaforBreakfast]

A bad idle is the toughest thing to find and fix
the dealer or repair person is just trying to charge you to replace parts and see what happens
They have trouble thinking out of the box sometimes with all the high tech stuff
I have plugged air leaks with plumbers putty and them fix them permanently later
You could have a problem with emissions equipment or exhaust as well as just an air leak

[NutriaforBreakfast]

Note the info the mechanic gave you says your O2 sensors are running lean
This is evidence of an air leak (to me) especially with the idle surging
First make sure the air box is tight then look at emissons and exhaust problems/leaks