Oil in intake manifold

Vintagesixtysix · September 2, 2023

Looking for help folks as wondering if solving this is economically viable to fix.

Self inflicted issue so a bit mad at myself; got into the wrong lane at a busy roundabout I use all the time.

Quick glance around, nothing special next to me so gave it “ the beans” in 1st & 2nd and beat the traffic over 80 yards + changing to correct lane.

VSC /EML / TRC comes on and I immediately feel power loss ( no stall) and throttle response goes numb. I’m now on smart motorway at this point so keep going to next junction.

Come off and do a quick roadside paper clip hack on OBD and car shows fault 051. Make it home ( only a handful of miles)

Had the car scanned and showing vacuum solenoid and lamda issue.

Smoke tested for vac leaks…. No problems.

MAF seems ok, throttle body ok.

Plenum comes off and it’s vey oily. Unclipping the sensor at the top right (PNP?? I think it’s something to do with idle) and there’s oil in the connector.

I bought a new vac solenoid, a salvage plenum + new OEM seals. All went on lovely.

Starts second time, running very rich but calms down as I guess the ecu’ s / lamdas start to do their thing.

Can’t clear the code, still showing lamda issue.

Test drive, acceleration still numb but mpg on readout starts to climb back towards normal.

Order new ( denso ) lamda sensor bank 1 pre cat. Ready to solve that.

Out of interest….. I disconnected the PNP again on ( new to me) plenum…… OIL? 😞

Strip it down again and I’m in same situation.

So…..
Have I missed a step to resolve?

Have I done something more fundamental to the engine? ( valve seals/ rings)

All thoughts gratefully received.

Is250 MTM

144k

Bought at 42k owned for 10 years +

No previous engine problems

Serviced to within an inch of its life

Does not burn any oil or coolant between services

Vintagesixtysix · September 2, 2023

Guys….. I can’t believe it.

Shes back….

10A EFI 2 fuse blown.

Replaced and seems to be back to normal.

Looks like I was chasing the wrong end of the problem 🤦

Didn’t show on diagnostics, I wouldn’t have guessed it would have even started ??

Anyway… I’ll disconnect the Battery and see if the lights disappear.

🤞

Vintagesixtysix · September 2, 2023

Oh…&

Does that mean an oily intake is ok at this age??

Linas.P · September 2, 2023

The oily intake is "semi-normal". Basically, it is because of PCV, so oily gasses went into intake to burned-off as per design. However, depending on how oily your intake is that could as well be fault PCV system.

In short - some oily residue in intake is normal with mileage, but loads of oily residue is not good. And all in all, oily residue causes more carbon build-up and not great for throttle body. To prevent that altogether you need to install oil catch can.

Vintagesixtysix · September 2, 2023

I still can’t believe it was even running…

Anyway…

I did replace the PCV at the the last spark plug change and I removed it & just manually tested the resistance of the valve when intake was off…. It seemed ok ( id kept the old one for some reason so could compare)

I will have a look at how to install a catch can as I’m intrigued how much oil is involved. 👍

Linas.P · September 2, 2023

Generally speaking not much, but enough to cover all intake system in fine mist of burnt oil and petrol, and it is just nasty.

I am sure somebody on here had catch can installed and after half of a year it was like 80ml of oil, less than quarter of catch can but as you can imagine, that is 80ml less dirt going trough the engine. And just generally, 80 ml does not sound like much, but imagine throwing a cup of dirty oil on intake manifold and how that would look.