Please help advise.
I don't know what I'm looking at here.
Rencently, my buddy gave me back an '85 GS that I sold to him a few years ago.
Totally stock, NO mods.
I gave him $0.00 for the RX7.
I babied the car when i had it. (my friend did not)
It sat for the past 2ys under a pile of boxes, garaged.
Minor dings. Faded paint.
Absolutely NO rust.

Drove it the 80 miles to home.
Stumbles a lot in the low and med rev range.
150K on the ODO.

While I was changing the oil I notice a GREEN foam in the oil filler tube. Looks like coolant. Could it be that the coolant ate away at the alum. housings during its hibernation? The oil was way past due and dark brown. Couldn't tell if there was water mixed with the oil. Did the oil chg with after warming the engine.

Plugs are clean.
No smoke.
Starts all the time.
Idle is ok, but stumbles on accel.
Primary cat is hollow.

I can't see affording an engine rebuild anytime soon.

Should i panic about the fate of the engine?
What actions should I take?
Thinking about getting a tune up.

I was hoping to turn this RX7 into a streetable Autocrosser and occasional track car.

Many Thanks!

 

I dont know about the coolant thing, but about the stumble, you should change the fuel filter for 5 bucks.

 

When coolant get 's in the oil, it turns to a mocha milkshake. If it's only in the filler neck, it's condensation.

 

Top it up and dive it a bit, Then check your water level to see if it is going down any.

A leaking coolent seal can be driven if it is not over heating any.