It Must Be Something Simple!?!
 

I have a 1984 380SE that runs rough for 5 minutes when it is cold. It starts right up no problem, but when you put your foot into the throttle it sputters, backfires out the intake and can barely rev up. If it idles and warms up for 4-5 minutes it runs perfect and revs up strong with no hesitation. Is there a sensor that could be bad or something? Everything else is good just the first 4-5 minutes when it is cold it hardly wants to run. It is a 3.8l (116 engine) and 126 chasis.
Thank you for the help. :)

Longshot, but look in the distributor cap for oil, if you find any change the o ring on the distributor shaft, the oil when cool will foul the inside of the cap and when it heats up it drains down

I thought it might have something to do with that, but replaced the cap and plugs with no improvement.
Thanx

the most likely cause is lean running cold, when the O2 sensor circuit is not working and the engine is running in fixed mixture mode. This can be caused by a fairly large vacuum leak (highly likely by this age, all the rubber and plastic is brittle), a bad EHA, a bad fuel distributor, etc. Even a bad fuel pump relay or tired pump can do this.

Best thing to do is check for vac leaks first -- if you just adjust the mixture, it will have to be done again when it get so bad you have to fix the leak....

From there, you need to determine fuel pressures, etc -- time for a visit to a tech unless you have the proper equipment.

Anything beyond fixing vac leaks or replacing a bad EHA begins to get VERY expensive these days...

Peter