Rich running 2011 NC2.0

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: __ 2011 2.0 Kendo
  2. I’m based near: __ Edinburgh
  3. I’m looking for technical help or recommendations on: __ rich fuel mixture/something not right.

Hi all, have a 2011 kendo 2.0 with 29k on clock. Picked up April after many years of wanting an Mx-5. Car is in really good shape on top and underneath.

Car has a few issues I think are related and despite many internet searches I’m looking for some advice.

Firstly no error codes being thrown up at all. Car smells of fuel on start up and can be quite eggy smelling when I stop and get out car or sat in traffic. Usually a cat issue I know but generally it’s not just a swap of a cat and it’s sorted.

Car is standard with exception of a sports panel filter and a gravity performance back box.

Driving car is fine but when coasting or running steadily along it has a very subtle surge on and off. Air con is off at this point. Exhaust tips at bottom get a dry soot deposit on them regularly. No smoke visible. Car seems to seem to suffer a bit from idle droop in that it needs a wee blip of revs before pulling away. Water temp sits at just a shade below half way on needle.

I’ve done a few things such as replace plugs with iridium NGKs, replaced MAF sensor and cleaned out throttle body replacing the gasket.

Head thinks it’s either EGR valve or the upstream o2 sensor but expensive and time consuming to fix it it’s something else.

Have the torque app and ran car up to temp and took a blast locally and captured the below.

Top left is short term Fuel/air mix and top right is long term.

Other 4 widgets are showing sensor 1 voltages etc.

Any help or thoughts appreciated.

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2

What fuel do you use? I suggest a tank of super unleaded and put the standard air filter back for starters.

3

Shell V Power used.

Air filter panel is a Pipercross panel filter. Would that make much difference?

4

If the filter has been over oiled - the oil can coat the MAF sensor and mess up the mixture.

5

I’ll fire in the paper one. I’ve cleaned the MAF and also replaced it but even temporarily it doesn’t cure it. Will try it though.

Thanks both

6

Whilst you have torque running - have a look at the AFR
Should generally be around 14:1

7

These are the reading I get when I run that just now. Not sure if it requires a full run out and up to max temps or not.

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8

Some decent fuel ( V power gets my blessing) or perhaps a decent fuel cleaner product followed by a good Italian tune up session will often help before you start pulling things apart.

My 2015 s2.0 sport tech responded well to this. I think the previous owner was possibly an “ over cautious” driver :wink: . These engines really do like to have their throats cleared regularly.

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9

That is pretty healthy AFR - shouldn’t be running rich at that.

10

I know of an NC that gave surging characteristics, after hours (and hours and hours) of engine diagnoses, it turned out to be a faulty wheel speed sensor. My opinion was that the DSC module was receiving an incorrect wheel speed signal and thought that slip was occurring on that wheel, so it sent a torque reduction request to the PCM. if you can, it might be worth monitoring the wheel speeds on your app.

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