Re: Got my Coupe GT back...quick story

[Scott Fisher <sefisher@cisco.com>]

Carter J says:

> Needs a tune up, it dies about 5 grand.

Define "dies."  

If forward motion ceases as though you've run into a tree, then kicks
back in when you get below 5k, and sort of cycles there as long as
you're stupid enough to keep your foot down hoping things will improve
(who, me?), try jumpering the two large slots on your fuel pump relay
socket, THEN go see how high you can rev the motor without dying.  You
should probably back off around 6500, just for grins.

There seems to be a common problem on CGTs -- I bought mine this way 9
months ago -- of previous owners having replaced the 5-cylinder fuel
pump relay with a relay for a 4-cylinder car.  Problem is, the FPR
includes an integral rev limiter, which cuts off the fuel pump when it
thinks you're going to overrev the engine.  And, you guessed it, the rev
limiter counts ignition pulses, of which there are 20% more at any given
RPM on a 5-cylinder car than on a 4-cylinder.  So (about) 5000 RPM is as
many spark pulses per second, in an I5, as (about) 6700 (or wherever the
rev limit is) in a 4-cylinder.

The reason appears to be that the 4-cyl relay costs around $30 and the
5-cylinder costs $120.  If this is your problem (and the jumpering the
two large sockets on the fuel pump relay panel will determine this),
order a new 5-cyl relay from Linda at Carlsen, and ask for the Quattro
List discount.  I paid $83 instead of $120, thereby nominating Linda for
sainthood in mine (and perhaps most important, my wife's) eyes.

On the other hand, if by "dies" you mean "loses power, stumbles, hiccups
and runs rough," you might try a couple tanks full of Techron and a
series of Italian tuneups.  (Italian tuneup: revving the car to redline
in as many successive gears as you have room, and freedom from
enforcement, to get away with safely.)  I found that for some time after
replacing the fuel pump relay, my '83 CGT would still buck and stumble
over 5000 RPM, apparently because the injectors weren't used to flowing
that much gas and had gotten partially plugged with varnish and crud;
the car was running lean at high revs and would knock, even at 92 octane
(and on my car's 8.2:1 CR).  Running a double-sized bottle of Chevron
Techron in a full 14 gallons of gas, plus using exclusively Chevron gas
for the last couple thousand miles, has cured that completely.

For a car with such low compression (at least in my car's case), I have
observed, the Coupe GT seems extremely sensitive to gas quality and
octane.  Anyone know (for a fact) why?  I'm reluctant to bump the timing
(as suggested on Huw's page) till I have a solid understanding of what's
going on. 

--Scott Fisher