- My model of MX-5 is: 2012
- I’m based near: Manchester/Chester
- I’m looking for technical help or recommendations on options to resolve engine oil consumption issues - short of dropping the engine if possible!
Afternoon all - I would really value some technical support/previous experience from the ‘hive mind’.
I have a 1.8l NC2 with just under 160,000 miles on the clock, which passed an MOT back at the start of July and hasn’t had much use since then. The engine runs fine, doesn’t knock and idles smoothly but recently I got an Engine Warning Light on the dash and when I pulled the codes I got P2096 -FF error code - Post Catalyst Fuel Trim System Too Lean. After some digging around I noted that this error can be associated with contamination of the sensor. Today I checked the Oil level which was below minimum but was filled by the garage at the same time as the MOT - so less that 1000 miles ago. I’ve never noticed any smoke from the exhaust but the Tailpipes are black with soot, which definitely indicates that this is where the Oil is going.
I carried out a Compression Test as per the Haynes Manual procedure and got consistent readings of 250psi on all four cylinders. I checked the Spark Plugs, also new at the MOT, and the two from cylinders 3 & 4 were a bit wet - see pics. I used an endoscope and had a look into each cylinder to find the piston crowns in cylinders 3 & 4 were coated with burnt oil - see pics. Cylinders 1 and 2 looked in great condition, with just a ‘normal’ coating on the piston crowns and the markings on the crowns still visible.
Given that the Compression Test doesn’t indicate any loss of compression and the fact that it’s only affecting two cylinders not all four, my thought process goes like this:
If the PCV was faulty, I would expect contamination in all four cylinders - as it’s only two cylinders could it be Valve-Stem Oil Seals?
I am also wondering whether it’s the Oil Control Rings on Pistons 3 & 4 that have got stuck and whether there’s anything I can put into the Cylinders to potentially clean the burnt oil that might be gumming them up.
Any thoughts or guidance based on previous experience of these engines would be very much appreciated.
