I had 2 Cadillacs with the 4.1 motor a 1987 Deville and a 1987 Eldorado and I had to replace the Cams in both of them.after that was done I never had a problem with them again.I heard some time ago that GM knew they had a problem with the 4.1 and offered current owners an upgrade or replacement.
I remember the 4.1 when it was first introduced. I was driving a 78 Coupe DeVille and did the one-time mistake of falling asleep on the interstate. After plowing through 160 feet of pine trees, the car needed to be replaced. I got an 80 model Eldorado and then decided that front wheel drive was not for me. I then got an 80 Coupe the following year and the 81 V864 the year after that.
When 82 rolled around, I went down to Cadillac to make my annual trade. Then I drove the new "improved" HT4100 with the chrome valve covers.
I can not even express how disappointed I was
For the next 12 years I kept going back waiting for them to get it right. My 81 Fleetwood had 330,000 miles on it when I finally replaced it with my 94.
I now have 292,000 miles on my 94 and I am still waiting for Cadillac to build a suitable replacement.
I would stay away from the 4.1L engine a.k.a. "HT4100 DEFI", the V4-6-8, and the troublesome diesel. These engines were concieved after the fuel crisis of the 1970's and the desire to make big cars more fuel efficient. They were all good ideas, but failed to live up to expectations in the real-world. They delivered trouble and caused Cadillac to lose come customers. There are still "survivors" out there and people who have been successful with these engines, but I still say they are far from Cadillac's best.