White smoke clarification

[LonelyDrifter]

So my car was putting out black smoke, and i had an exhaust leak b/t head and manifold. I took the manifold off, replaced the gaskets, bolted back on, and replaced the O2 sensor for good measure. Now I have white smoke from the tailpipe (and a new leak b/t the manifold and exhaust pipe...)

I saw an earlier (2004) post about white smoke. "Thinner" smoke meant a rich condition and "thicker, puffy" smoke is coolant. I think mine is thinner. I've always thought a rich condition would be black smoke though. Any thoughts?

The same post said to check the coolant temp sensor and airflow meter. How do I conduct a ECU pin voltage test to check these? Does it require taking the "harness" out of the ECU? Im sortof a newbie to diagnosis electric problems, hardly know how to use a multimeter...

thank in advance!

[LonelyDrifter]

Sorry, I have a '90 240sx with a SOHC. I didn't specify...

[babowc]

black - fuelwhite - oilwhiteish blue (sweet) - coolantrotten egg - cat

i fixed my problems with running rich by just changing out the fouled o2 sensor and spark plugs

[LonelyDrifter]

Well, I started it up again today (daylight this time). At first, it smelt rotten (for a minute). Then, after it warms up, the white smoke starts. I'm going to try an upload a pic. I'm not sure it was a "sweet" smell, but it wasn't anything I've smelled before. Almost like a "kettle korn" smell, or something burning.

I already replaced the O2 sensor and my plugs (used NGK). That, and fixing my exhaust, led to a change in smoke color - black to white. I looked at the MAF connections, and they look clean. Tried to clean the coolant temp sensor too (it had a little corrosion).

[babowc]

maybe its steam from how cold it was outside..but im sure thats not it.

i forgot what i did to fix this..all i did was the o2 and plugs.. it happened when i was first learning to drive the car.

anyways, i guess if its burning oil.. maybe check your compression. maybe the rings are shot?

im a newbie at tech.. just putting up possibilities.

[LonelyDrifter]

Thanks for the reply. I'll try to check the compression, and see what it says. Ill be gone for the rest of the weekend, but will be back to update any results. Any more suggestions would be greatly appreciated! Also, if anyone could help me with a procedure (specific) on checking pin voltages on the ECU, that would be helpful. I did search, but Im too electronically stupid to know...