Hi. I have owned a Fiesta MK6 1.25 2014 for 2 years. It has been reliable but developed a revving issue a few weeks back. It ticks over fine but can then jump from about 900rpm to 2000 rpm. This happens when driving too. A blip on the throttle can sometimes cure it, dropping the revs back to normal.

After Googling a fair bit, I replaced the air filter and took off the throttle body to clean (it was already very clean). I also had a garage do a smoke test to check if any vacuum hoses were damaged or leaking. When it was still doing the same thing on the revs, I took off the throttle body and cleaned the wipers on the circuit board's fly-by-wire unit (I have good experience with handling electronic stuff btw). I did notice evidence of engine oil behind the butterfly this time though on the engine side. I dipped a clean rag into the intake where the throttle body mounts and it was pretty full of oil, so I removed as much as possible and reassembled it all. It seemed to run perfectly for a few drives.

This week it got a lot worse though, happening more often and also now cutting out a few times when waiting in traffic which it has never done before. There's no MAF sensor on this car but I believe there is a T-MAP sensor which I intend to clean or replace. The engine seems to rattle a bit too occasionally.

1. Anyone seen this before?
2. Can the T-MAP sensor cause this issue?
3. Do you think the oil might point to piston rings failing or something else?
4. Is there a drain in the inlet manifold for that oil to escape that might be blocked?

I'll pull the plugs when I get a chance too. Thanks in advance for any help.

 

 

The oil breather valve (PCV) would be the next thing to replace here.  That should only allow a small amount of oil vapour past, not a load of liquid oil.

Thanks @TomsFocus. I have the PCV valve, will try to fit asap and let you know.