I have a 1990 thunderbird sc just rebuilt eng idles rough & misfi

you probably have an intake gasket, is it running real rough?
or its the head gasket leaking and if you have gotten the head pretty hot it may be cracked?

What happens if you give it a little gas ? Hold the RPM's up , will it keep running then ? How does it Idle , smooth or ruff ? Does the idle seam low ?

When and eng gets that hot the rings can calapst you my have to rering and hone the Cly

Possibly a blown head gasket, letting coolant into the cylinders to be burned. White smoke is usually coolant burning. Have the engine's compression tested to verify.

This code doesn't cause any lack of power, the fact of the matter is that code 25 is most likely a symptom of the problem, the engine has excessive spark knock being sensed. Have the engine compression tested and have it checked for a misfire. Also have the fuel pressure tested, low fuel pressure can cause this lack of power as well/

It just clicks, this indicates problem with battery or problem with starter.If starter is faulty then battery will just give power to starter and click.The engine will not start due to faulty starter.Most likely starter is faulty, but if both battery and starter checked out ok then there are other possibilities too.Click the link below:-- http://technoanswers.blogspot.com/2011/06/1990-thunderbird-sc-when-you-turn-key.html----------------- This should help.Thanks.Helpmech.

Should be in the power distrubution box near the battery. Also, there is a fan control module mounted on the right radiator support towards the top engine side

CHECK ENGINE COMPRESSION.SOUND LIKE YOU HAVE WORN ENGINE VALVES AND PISTON RINGS AND VALVE SEALS IF ENGINE SMOKING BLUE.IF YOU ARE GETTING HEAVY WHITE SMOKE.YOU HAVE A BLOWN HEAD GASKET.WHEN DOING COMPRESSION TEST IF COMPRESSION READINGS 90 - 80 WORN RINGS 60 - 40 BLOWED HEAD GASKET.

i would crank the car when it starts reving up and down take a tool of your choice depending on the position of AIC and while acting up firmly tap on it for a few seconds and while you're doing that listen for the enging to change what it's doing.sometimes you can tap on them and get lucky.but if the enging clears up or gets worse when you tap on it you've pin pointed your problem for sure. hope i helped..

You could try faxon.com. They deal in old service manuals. They are manufacturer's service manuals for the dealerships and cost in the range of $50 to $75 each plus shipping.