very slow acceleration

I have a 86 model 740 who hesitates on acceleration. I have replaced my spark plugs, but that did not help. I have also checked the wiring to my
temperature sensor, as I have seen a posting about the subject in this news group.
The problem have been for quite a while, but in the beginning it was just periodical. Now the problem is persistent.
Any suggestions ?
regards Kjetil
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