So my wife's '94 Civic DX Coupe 5 speed was running wierd Monday morning when she was leaving for work. She said it had been running fine the last week. But when she came back to swap cars, there was a lot of smoke comming from the tail pipe, (it had done this a few times before, but cleared up) and was reving up and down like there was a vacuum leak.

I checked the oil. Clean as can be. Started it up and let it run for a while. When it got warmed up, I was reving it and smoke started coming out of the tail again. Then it started revng up and down again.

Checked the coolant. NONE!?!? So could that be the cause of the reving? The IAC was probably empty, and that could cause it to rev like that right? But what's weird, was the oil is perfectly clean. No milk. I've dealt with other blown head gaskets before, in many different kinds of cars, and all had the milky oil. This oil is almost brand new. Oh, yeah, and there is this goop in the coolant. At first I thought it was oil, (which it could be) but after playing with it it seems like what happens when you mix the green and the red together. But we haven't done that.

A little background: It's a DX but has a VX (vtec-e) motor in it. She got the reciepts from the swap the previous owner did. And it was done at a shop. She has had it for atleast 8 years now. About a year and a half ago I replaced the timing belt and the water pump. Could I have installed it wrong or something? I mean it was over a year ago, and something would have happened right away right? They are dealer parts, and they are for this motor. I first got the wrong parts, then returned them when I pulled it all apart and found out they were wrong. The dealer gave me the right parts.

I did a compression test and it came out as:
#1 192psi
#2 176psi
#3 174psi
#4 184psi

All spark plugs were pretty black, but no deposits on them.
Any help would be apreciated.

 

A blown head gasket can make a engine drink coolant like a high schooler at a keg party

It dosent have to mix with oil

 

What color smoke: if whitish blue? That with lower comp numbers #2 and 3 seemed to indicate a very good possibility of HG. With no coolant and if you have no visible leaks then it seems its getting burned=whitish/blue smoke. Like you said the up and down rev=IACV missing coolant
And ditto on it being too long for the timing belt etc to have been installed wrong.Yeah you would have noticed it right away.