Ford Explorer: '93 knocking/pinging disaster follow-up

On Wed, 29 Oct 2003 01:22:21 GMT, "Ron N.Y"
<net> wrote:
 

I don't recall all of this thread so.... Have you cleaned your MAF
sensor (or replaced it)? My 92 used to ping in hot summer weather but
after cleaning the MAF is no longer pings. Others have traced the
pinging to leaking lower intake manifold gaskets that cause the
mixture to be too lean (sucks in crankcase fumes which dilute the
fuel/air mis). Is it possible you are running too hot a spark plug?
Maybe the wrong heat range got put in and they are causing a hot spot
and pinging.

I've heard conflicting things about that jumper you disconnected. One
story is it retards the spark 2-3 degrees but otherwise no other
changes. The other story is that it sets the advance to "base" and
allows no advance at all, hence the lack of power. I thought I read
it was to be used to check base advance which lead me to suspect the
second story was the true on.

I tried the jumper approach too. It caused less power and reduced gas
mileage. I put it back on and ran high test from then on.

On Tue, 28 Oct 2003 23:32:40 -0700, AZGuy <net>
wrote:
 

Yep that's what I just did . The power reduction was too severe so I put the jumper back in and it runs much better with high
octane anyway with more power .No pinging with the high octane gas so far . I was wondering if anyone with this problem tried
using one of those performance chips to help on this problem , I didn't hear anyone mention it . My MAF sensor was clean ,
there was no EGR valve , and the bolts on the intake manifold were tight . So high Octane it is , I give up ! Thanx for all
the help out there !
Ron

"John Shoemaker" <yahoo.com> wrote in message news:com... 
from 
loose 
Tried 
octane 

I didn't notice any loss of power in our 93 Expl after removing the
pin. The truck runs great. However, I haven't put it on the dyno for
a before and after.

I did try using higher octane gas before removing the pin but that
didn't stop the pinging. As more miles are accumulated on the engine,
more carbon builds up in the combustion chamber and cylinder pressure
increases. Firing this old engine at the timing specified for a new
engine will then cause the engine to knock.

I can't agree that removing the pin will set the timing to the base
value with no advance at all since there is no noticeable difference
in driveability (at least for the 93 Exp).

Before retarding the timing our Exp only knocked under mid to high
accelerations, but the sound just sent chills down my spine, very ugly
sound. I think Ford was trying to squeeze every ounce of fuel economy
out of this engine so they timed it on the ragged edge, just below the
knock threshold. Some newer cars use knock sensors to keep the
ignition timing as far advanced as possible (to increase fuel econ and
power) but avoid knocking by pulling back timing according to the
knock sensor feedback.

If higher octane gas with the pin in place is most economical then
that is what I would do; provided the knock was gone. However, if
lower octane gas with the pin removed was most economical then that
would be my course. It should be perty easy to do some fuel economy
measurements with both configurations and come to a conclusion.

Hope this helps,

Tom



"Ron N.Y" <net> wrote in message news:<hDEnb.13527$srv.hcvlny.cv.net>... 

Some of the discussion here sounds like pinging is normal as the truck gets
older. I'll just input here that my truck has 193,000 miles on it and it
doesn't ping.

It used to ping, but I found some info about the lower intake manifold
gasket leaking because of a poor design. The #5 spark plug would carbon up
so that you could see the difference between the other spark plugs. Some
folks replaced the gasket with success, ie. the pinging went away.

But, I found that the intake manifold lower bolts loosen with engine cycles.

So, you might want to just tighten the intake manifold lower bolts, very
carefully, in the pattern recommended in Helms. They only tighten to 180
inch pounds or so, so make sure you don't overtorque as you might crack the
intake manifold.

I don't think pinging is normal. But, sometimes, the root cause is hard to
track down.