There are basicly two kinds of "off the shelf" Fuel Injector (FI) cleaners...those that work quickly and those that are less aggressive and clean over a longer period of time. I'm talking about the stuff that goes into your gas tank. But then, name-brand gasolines have additives -- -- like Chevron's Techron -- which are SUPPOSED to keep your FIs clean all the time.
You could try the "gentle" cleaner for a few tankfulls and see if that does anything re: restoring power, then go to the stronger additive for a tank...Chevron bottles Techron but there are a bunch of brands of FI cleaners. If all that does nothing, you can always take it in for a professional cleaning...I don't see why such a job could cause trouble for your engine.
They take the FIs off to clean anyway, then reinstall them, so stuff does not "break loose" and go into the combustion chamber...if it does, it's coming from somewhere else. See this site for an overview of the FI cleaning process:
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Of course, this is assuming you ARE correct in the first place that the FIs are dirty and THAT is what is causing the power problem.
Good luck,
John D.
I have a 94 Sentra that just hit 190000 km (118000 mi). The car is in
> decent shape, but the engine seems to lack a bit of power.
>
> Since the previous owner, who bought the car new, never had the
> injectors cleaned (so he told me), I figured it could be a good idea
> to have the nearby Nissan dealer do the job. (We had the job done on
> my wife's car, also a 94 Sentra, some years ago and today is
> noticeably more powerful than mine even at 240000 km [150000 mi]). >
> Surprise! The dealer told me I'd better think twice before doing
> this, because the stuff they use is so powerful that it could
> seriously damage the engine given the high mileage and the fact that
> it's never been done on the car before.
>
> Has anyone heard of a damaged engine following a professional
> cleaning? What about those off-the-shelf chemicals? I heard stories
> about clogged injectors from detached bits of gunk following the use > such products. >
> Any advice is appreciated.
> Serge