[1993 NA 1.6 B6P] Oil deposits inside fuel injector housing - Is my engine on its way out?

[Kacper-K]

1. My model of MX-5 is: 1993 Eunos Roadster 1.6 (B6P) NA6CE 212-XXX
2. I’m based near: Yorkshire
3. I’m looking for technical help or recommendations on: Engine condition

Hello All,

I’m currently doing some recommissioning work on my Eunos Roadster. I recently took the intake manifold out as part of some other work I’m carrying out, and to my surprise I found oil between the manifold and the gasket.

I suspect that his has happened as a result of a cam cover gasket leak which went un-noticed a few years ago, with oil slowly working its way around the engine, and over time with many heat cycles inbetween the intake manifold gasket and the engine.

My concern here is that I can see where oil has ended up being deposited around the fuel injector housing (And inside the intake manifold, but that’s not a concern as I’m going to refubrish and clean it out).

I’ve included a few pictures here to illustrate what I’m talking about:

I can see that the part of the chamber which is is sprayed with fuel by the injector is relatively clean, however the outer housing has a thin layer of what I suspect is burnt oil.

I was really hoping to get a few on opinions on the following:

• Is this likely to have caused any long-term damage anywhere within the engine ? Is there something else I should inspect and check ?
• Can I get away with simply cleaning the injector housing with some sort of a product like carberutor cleaner that won’t affect combustion ? Would this be sufficient ?
• Am I potentially looking at an engine out job ? Would the engine need to be taken apart and re-built for a thorough clean, or potentially replaced altogether ?

Any advice or suggestions are appreciated, as I’m still considering what steps I should take next

[Martin_Young]

My first thought is it’s most likely the buildup from a small amount of engine oil vapour getting sucked into the inlet manifold through the crankcase breather valve over the years, in which case it’s probably nothing to worry about.

[Kacper-K]

Thanks, I’ll try and give a good clean before I re-assemble everything.

Do you think this would also be the explanation as to why the inside of the intake manifold is all oily/sooted up ? This seems to go as far back as the throttle body, which obviously stopped it with the throttle valve.

[Martin_Young]

Yes, I think so. It’s had 30 years to build up after all. First time I took an inlet manifold off I was a bit surprised but it looked much the same.

[Mazda_mender]

Does she smoke on start up or taking off from lights?, that just looks like standard pick from the rocker breather hoses from being used hard, check the baffles etc.
M-m

[Kacper-K]

No, I’ve never noticed any smoke at all on startup, idle or when moving from stationery.

I have noticed the exhaust tip looking a bit sooty, but I put that down to the engine running a bit rich potentially.

What would you recommend using to clean the injector housing ? I was thinking maybe petrol ?

[Mazda_mender]

Then there is nothing major afoot bud but find which hose is feeding oil off the rocker cover, the only true way to clean the inlet is to remove it ,split it from the throttle body.
Give it a deep clean ( i’ll dig some pics out) with some product we use and recommend Mazdamenders jizza clean, and just re fit ,job done , it is easy enough to remove to do the job correct.
M-m

[Mazda_mender]

M-m

[Kacper-K]

That’s brilliant, thank you for the advice & help. Much appreciated !