How many miles are on the car? If a lot, I'd give the car a basic tuneup &
work from there.

1.) Clean MAF sensor with electrical parts cleaner only
2.) Clean IAT/ACT sensor with electrical parts cleaner only
3.) Check/clean/replace air filter (depending on which type you have)
4.) Test/regap/replace spark plugs
5.) Test/replace ignition wires
6.) Replace fuel filter
7.) Check/clean/replace EGR valve (very neglected--and recently the cause of
my pinging problem!!)

I'd try those first. If you do all of that & the pinging is still there...
ya got me! My car started pinging with 91 octane... so I cleaned the EGR
valve & pinging went away with 87 octane even. Good luck, bud.

-Mike

--
A happy kid behind the wheel of a 98 Mustang GT
Cold air intake
FRPP 3.73 gears
Steeda Tri-Ax Shifter
Full Boar turbo mufflers
Hi-speed fan switch
255/60R-15 rear tires
Subframe connectors

Scribble I'm coming in while missing the initial thread, the gasket goes to
the EGR solenoid switch located on the passenger side firewall.
If this pinging started after your last re-fuel it could be bad gas, the
injectors may be dirty an easy corrective would be to burn out or empty out
the tank (This won't be easy) or get an octane booster and injector cleaner
and put it in and fill the tank with fresh gas. If the ping stays I
recommend that the ecm needs to be tested to see if any fault codes pop up.
The ECM may need a "re-flash".

It's common on the 94 and 95GT's. I had a 95GT and it did the same
thing. I pretty much replaced/cleaned all the parts that are mentioned
in this thread and it was still there.
Then around 60K the HALL effect sensor in the distributor crapped out.
Dealer replaced it and when I got the car back the pinging was
completely gone ! At first I thought they backed the timing out since
they had to remove the distributor. I played around with it, bumping
it up quite a bit but I did NOT have any more pinging. Car ran great
until (and beyond I hope) I sold it at 92K. miles.

Two other things I would do also;
-Check the fuel pressure. Get (or borrow ) a fuel pressure tester and
run the test. See if it builds up enough pressure and if it holds the
pressure after switching the engine off.
-Run some Seafoam in your gas. This is a very strong cleaner that does
wonders. I think carquest sells it. not many others sell it.

How many miles does the car have on it ? Mine started pinging pretty
early in its life (30K or so ?)

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I had the same problem, where the pinging gradually got worse until about at
75K miles the check engine light started coming on.  The translated error
code was "lean condition."   A dirty (or bad) MAF sensor was the problem.
Replaced it, and the pinging went away, and the car ran as good as it ever
has.  ( a lot of times you can get away with simply cleaning the MAF sensor,
if you're careful not to break the thin wires).

The odometer just went over 100K miles today, and it's still running great!

-Bill
95 GT 5-speed