350Z - "Knocking" / Uneven running 2005 UK model

[tenchijin]

Hi All,

 

So my 350Z is running really uneven and I'm really lost as to why. Here's the story so far.

I brought the car just over a year ago and about 2 months after I brought it, it just started running so rough it was un-drivable. I took it to the garage, turns out the garage I brought it from had stamped the service book but not actually serviced it!

This resulted in the clogged air filter collapsing in on itself and drawing dirty air into the system. So I had this replaced and mass air flow meter cleaned by a Nissan main dealer (not the garage I brought it from).

 

Ever since that it has been running really uneven. I took it back to the Nissan main dealer and was told I needed to replace the mass air flow meter, which I did (although it was a breakers yard part), this made no difference. They also cleaned the throttle body and I have had new plugs fitted.

 

But still it pops and knocks quite badly when idle, although it seems to ease off a bit if I have the air conditioning turned on?

 

The Nissan main dealer I took it too last said there were no error codes present and the OBD2 scan tool I have confirms this.

Looking at the LTFT values on my scan tool, it appears to run constantly at about +5% which having done some rudimentary research doesn't look correct? Although correct or not, I have no idea what would cause it or how to resolve it.

 

So I am at a bit of a loss, my next option with the garage is to authorise some very expensive diagnostic time, which I'd really like to avoid.

 

Any suggestions will be greatly welcomed and I can provide any additional info required within the bounds of what my scan tool can offer.

 

Thanks for reading and your time in advance

 

Dave

[Dom187]

LTFT always at 5% hmmm thats a reading from the MAF right?

 

Have you tried an ECU reset?

 

Do you know anyone who has a Zed? I would try swapping out the MAF for a known good one and see if that works. I know from when I had my Golf, the cars dont seem to know when a MAF has gone bad from my experience.

 

Maybe worth a shot? Where abouts are you located?

[tenchijin]

Not sure if the LTFT comes from the MAF to be honest, I have 2 readings a LTFT1 & LTFT2 which both hover around the +5% mark

 

Not tried the ECU reset although the word "reset" disturbs me slightly

what are the implications of doing a reset?

 

Nope, dont know anyone with a Z unfortunately, I'm based just outside Reading, Berkshire

 

 

Thanks

[Lexx]

No implications of doing a ECU reset.

Its just makes it "forget" you're driving style that its adapted too, and clears any limiting errors.

 

It is achieved through the so called "pedal dance" - pressing the pedals in a set sequence.

There is a guide in the guides section.

[martinmac]

The rest is a little fiddly as its time sensitive but worth a try. The procedure is in the guides section. It wont cost anything so worth a go.

[tenchijin]

Nice one guys, I will attempt this peddle dance tomorrow and let you know if anything has changed!

 

Any more suggestions the mean time are still greatly welcomed

[Mark@Abbey m/s]

LTFT always at 5%

 

LONG TERM FUEL TRIM , sounds like the car is adding 5% fuel all the time , I would like to see if this is the same after you do a ECU reset.

 

I have seen this a few times on the 350Z's. My general thoughts would be as follows;

 

1, do a ECU reset ( this can be done 3 ways. 1, via the pedal tapping 2, disconnect ECU 3, use Nissan Consult. Then see if the car returns to showing LTFT very quickly.

 

2, I have seen these cars give this problem due to front lambda sensors starting to wear out , you can sometimes cure this by swapping the sensors side to side i.e left bank to right right bank to left.

 

3, It could be an airflow meter , but normally these when the start to fail make the car go into limp mod they wont rev over 3000rpm

 

4, could be an air leak after the Air flow meter does take much of a air leak to cause the ECU to try to add 5% fuel to make the car run correctly.

 

Where are you based in the UK?

 

Any more questions ask away.

 

 

Mark