I have the opportunity to purchase a well-cared for '99 Grand Prix
GTP. I am a bit unsure on a couple of fronts: first, is there any
data (anecdotal or otherwise) on the reliability of the supercharged
engine vs. the base 3.8? I put lots of miles on my cars (my current
daily driver is a '93 Bonneville with 165K and I need this one to go a
similar distance). What are the known failure points (and associated
repair costs) for this engine?
Also, this model year "requires" premium fuel (though later GTPs do
not). Is there a substantive difference between the two engines? Is
this a technical requirement (that is, will 87 octane knock or cause
other problems) or a legal one (to claim horsepower numbers or some
Thanks for any informed commentary.
I (we) have a 94 SSEi, supercharged. It currently has 180,000 miles on it.
I use Valvoline Synthetic oil. Did a compression test at about 150,000
miles, don't remember the nos. but it was like new. As for the
supercharger, I did add a little oil to it once. No other problems with the
supercharger. The dealer seems to want to blame other problems on the
supercharger though, such as a miss. Plugs and wires have been changed two
times. I've had to replace one injector and one coil on the coil pack. Had
the transmission seviced at about 75,000 miles and again at 130,000. I am
having trouble right now with radiator fan not running and AC not working
properly, I believe these problems are related to the computer, but I may
have to take it to the dealer to confirm. I do most of the work on my
vehicles myself, and take it to the dealer if I need help diagnosing a
Almost a year ago, I bought a '99 GTP with 90,000 miles. Before I bought it,
a friend of mine who is a GM mechanic performed a computer diagnostic on it
and everything seemed fine. Within the next couple of days, I'll be hitting
the 100,000 mile mark. So far, I haven't had a single problem with the car.
I've just done normal maintenance, nothing special and I've run premium fuel
Oh, I've driven it. My main worry is that it's too much fun,
especially with some relatively new drivers in the household, to last.
I very much appreciate all the posts. I started out worried about
the reliability of the supercharger itself and now I'm paranoid about
the plastic intake manifold problems described in another thread. I
maintain the cars well and don't mind wear and tear expenses but dread
those thousand-dollar-plus type failures that seem to plague most GM
cars at 100K or so (many of the 3.8s being notable exceptions). I
guess I'll have to accept this risk and the need to buy the premium
fuel as the price of admission, though.
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