P2177 error code and rough idle

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: NC 2.0
  2. I’m based near: Cambridge
  3. I’m looking for technical help or recommendations on: P2177 error code

Hi all,

I’ve done a bit of searching for this one, but not really found anything so far, so I’d like to see if anyone else has had a similar problem. A few months ago, after thousands of miles of trouble free driving, the check engine light came on my 2.0NC. I checked the code, P2177 - which means it’s running lean off-idle. I reset the code, carried on, and after a few weeks, it came back again. At the same time, I noticed that the idle speed was a bit lumpy - nothing serious, but every now and then there’d be a little hiccup.

Over the past few weeks this has gradually got worse, and now the error gets generated after only a few miles running, and the cold tickover is awful - hunting up and down between about 600 and 2000rpm or so.

Normally, I’d suspect a leak in the air system after the MAF sensor, but I’ve checked this quite a few times, and it all looks good. I’ve checked and cleaned all the connectors around the injectors, changed the plugs (I just happened to have some spare ready to fit - I didn’t expect this to make any difference!), cleaned the MAF sensor, checked the throttle body, checked everywhere for leaks again, ran a couple of cans of injector cleaner through the tank, checked one last time for leaks and still, no joy.

I’m beginning to suspect a dodgy O2 sensor, given the way the error came on gradually, and is now getting worse. But before I give it to someone with better diagnostic tools than me, does anyone have any other suggestions to try from past experience?

Many thanks all,

2

Hi
Google is you friend, I found this on a Miata website, see post 9

Not sure if this is mazda specific but the misfire and thoughts about the O2 sensor seem in the right area.
The fact the cold tickover is bad may indicate a pre cat O2 sensor heater issue, can be checked by testing the resistance on the circuit with a multimeter.
If you have an OBD reader that can poll live data this may help narrow things down.
try not to fire the parts cannon without data to back up the diagnosis.

Good luck

3

Just as an update to this, in case anyone else ever searches for it. I’ve not completely fixed the slightly lumpy idle, but the check engine light seems to be off, and staying off for now… what I ended up doing was removing and cleaning up the two solenoids on top of the engine (they’re listed as a Variable Intake Air Solenoid and Variable Tumble Solenoid [1]) and giving them a good clean up, and while doing that, I had the battery disconnected for 30 mins. One of these things seems to have made a definite difference. The hunting on idle has now gone, and the check engine light is off. Idle is still a little lumpy when cold, but nowhere near as bad as it was.

[1] VARIABLE INTAKE AIR SOLENOID VALVE INSPECTION [LF]