84 seville rough idol when WARM

[BL14869]

Looking at a seville(4100) idols smooth when cold .after it warms up a bit it feels like a miss but definitly rough idol after it warms up .any thoughts or ideas.a tune up i can handle but if its a computer glitch or block issue i think ill pass on the car.insights /experiences appreciated

[Geoff Newcombe #4719]

Are you familiar with the 4100 engine? Probably the most troublesome engine Cadillac ever built (maybe a toss-up with the 350 diesel, but the diesel wasnt strictly a Cadillac engine).  It has been described by some as a good boat anchor.  How many miles does it have on it?  Can the present owner verify the maintenance this engine absolutely must have has been done regularly?  If you cannot work on, troubleshoot, and diagnose this engines problems you should know someone who is very good at doing just that, you will get to know him very well.

Oh, by the way, the transmissions were weak too.

Been there, done that along with many other Cadillac owners of that vintage with that engine/tranny whose next car was a Lincoln.    

[Barry M. Wheeler #2189]

Ive been there, done that twice with the engine in these cars. Pull the dipstick, and see if it looks like anti-freeze has mixed with the oil. Then run, do not walk, to the nearest exit. When the gasket goes, it does so in the blink of your eye. I was driving to work one day, and all at once the car started running rough. Had it towed to the Cadillac store and found the gasket had ruined the engine. Even though it was still under warranty, it never did run right after it was repaired.

[TJ H 20664]

I dont hate those engines and transmissions as most people.  Yes they are prone to cooling issues especially the orignal ones.  With all the updates they are not that bad.  They are TBI systems which are fairly reliable and simple.  If you are thinking about buying one take it to a good shop for a cooling system pressure test.  If you own it a tune up is always a good idea.  After that check the base throttle setting and the base timing.  I have seen MANY of that vintage engines where someone has messed with the timing or throttle stop without understanding the proper way to set them.  Once you get them at the right base settings you may then find why they started messing with stuff in the first place.  The procedure changes depending on the car and year so be sure to have the right info.

[Don]

1500 hyndred dollar repair, like barry said, run, dont walk or ever look back