CONTAINS SPOILERS AND IDIOCY EVEN BY MY STANDARDS
It is hardly an earth-shattering revelation that Emmanuelle IV is rubbish. Copious amounts of soft-focus humping in exotic locales while tinkly Euromuzak slop burbles away on the soundtrack, glamorous women (and men) getting their kit off and going at it like hammers, supremely idiotic dialogue that makes the Star Wars prequels sound like Aaron Sorkin's pithiest, plotting that would shame a daytime soap opera: a 33-years-on recount by the Academy Awards is not on the cards. What there is, perhaps all there is, is a sense of disappointment as the previous third entry in the saga, Goodbye Emmanuelle, was probably the best thus far.
Of course, noting that an Emmanuelle movie this far down the franchise has terrible acting and a lousy script is like suggesting the last Woody Allen was short on car chases and had very little social commentary about gun control. That's really not its job. Even so, the stupidometer rarely dips below ninety in Emmanuelle IV. This is the one in which either Sylvia Kristel or the producers decided that she was too old (at 32) to keep on getting her bum out and so has extensive plastic surgery to transform her into the younger, slimmer, fitter Mia Nygren. Confusingly, she also changes her name to Emmanuelle from Sylvia, suggesting this is an entirely unrelated entry in the series as she spends the first act playing herself as a magazine journalist. But she still has her old memories of her all-consuming love for Marc (Patrick Bauchau, not in any of the previous films) - obviously, because she hasn't had her mind wiped or her memory implanted: this isn't Total Recall or Blade Runner. If there's any dick in this movie it sure ain't Philip K.
So Emmanuelle mopes around Brazil recuperating from extensive surgery, having sex, watching other people having sex, blathering on and on about her voyage of sexual discovery in a manner that you might describe as navel gazing except it's not even her own navel any more. Eventually she goes back to Marc, thus rendering the whole adventure redundant, musing that their perfect love meant they were destined to be together forever, even though  that perfect love didn't stop her from humping miscellaneous Brazilian randoms and  it's less a matter of predestined cosmic fate than a matter of flying to Paris, sneaking into his office and making dinner reservations for the two of them.
The fact that it's utter drivel, however, shouldn't have stopped it from being a good time. At least the earlier entries had a measure of exotic glamour about them and that's mostly absent here: it's got little more in the way of gloss and style than one of Joe D'Amato's artless knockoffs. To judge from his IMDb page and a brief trawl round Google videos, director Francis Leroi is apparently a hardcore guy anyway (this is soft as wet blancmange), though he subsequently made several small-screen continuations featuring flashbacks to a younger Emmanuelle as told by Kristel to jetsetting businessman George Lazenby. There's absolutely nothing in Emmanuelle IV to suggest that further entries in the series would be a sufficiently rewarding evening's entertainment.