Hi Guys,

Could use some advice, my 350z (an 04 with 60k on it, well taken care of) is having idle issues. It's throwing a CEL which is for cat converters and for MAF. The cat converters are invalid since I am running test pipes.

The MAF probably means the MAF is shot, so I did the logical:

1. Clean the MAF properly with MAF cleaner, reconnect it.

This has improved quite a bit but still not where it should be. Every 30-40 seconds it will drop 200 RPM's and act like it is loosing out, but then it recovers and idles well again for 30-40 seconds. In normal driving operations it does not have issues.

So I advanced to:

2. Remove MAF sensor and start car, this creates an Open loop. In theory Idle should hold at 1,000 RPM's steady (or so I have been told),

When I do this, the idle does hold much steadier at 1000 RPM's but again every 30-40 seconds it will drop 100-200 rpm's and then quickly recover.

The issue is not constant, sometimes it will go 3-4 days without any issue what so ever. If the AC is turned on it does -not- do this.

This leads me to believe it's:

1. MAF sensor
2. Throttle Body
3. Vaccum leak

I have almost ruled on 1 because even when the MAF is disconnected the issue persists.

It could be the throttle body, a vaccum leak is not likely as I have already checked carefully and did the soapy water check.

What I am wondering about is why the CEL says it's the MAF ... is the most likely issue still the MAF even though with no MAF the issue exists?

Any advice would be great just want to figure out where to go.

Also my mechanic said it's the MAF based on the computer and wanted to replace it. I would agree but even with MAF disconnected the issue exists.

Here is a video of idle with the MAF and without MAF connected.

http://www.youtube.com/watch?v=ilwJq...ature=youtu.be

Thanks in advance.

 

try disconnecting the battery and doing an idle air relearn
thats the easiest and most inexpensive first thing to start with. i had a choppy idle when the weather changed (went from 110 dry heat to 90 humid heat) and when i tried that the idle would go back to normal.

 

My Z was idling rough after test-pipe install. Had to get a tune to fix that.

Cleaning the MAFs is worth a shot

 

I remember when i logged my car with the MAF sensor disconnected, The idle was fluctuating and was never steady at 1K rpm as you say !!!

 

Thanks x 3.

I have a test pipe - so that could be part of it.

Also the MAF off - rough idle - did not know that, when I was studying to be a mechanic I learned MAF off - open loop should be a steady idle depending on the car, never studied Nissans.

I am worried now though I may have a bigger issue... my exhaust smells sweet, almost like anti-freeze and to me that means bad Head Gasket. Car has never ever over-heated, so not have any forced induction mods and only 60k, as unlikely as it seems the HG is bad, I am getting a tad bit of white smoke and quite a bit of a sweet smell from the exhaust. Oil is not muddy and anti-freeze does not bubble in radiate when car is running.

I am taking her in for a leakdown and compression test tomorrow. I am super paranoid at this point.