1995 Ford E350 RV 460 Pre-detonation Problem

The truck has 15000 miles on it and has been thru 3 engines due to
pre-detonation. Timing is correct but jumps around a bit, have verified
chain to be OK. has new distributer and pickup, ICM checks OK, Ive been
thru idle air , map & 02 sensors , any ideas what else could cause this
condition besides fuel quality???

lugnut wrote:
> On 28 Jun 2006 18:30:23 -0700, "dabworth"
> > wrote:
>
> >The truck has 15000 miles on it and has been thru 3 engines due to
> >pre-detonation. Timing is correct but jumps around a bit, have verified
> >chain to be OK. has new distributer and pickup, ICM checks OK, Ive been
> >thru idle air , map & 02 sensors , any ideas what else could cause this
> >condition besides fuel quality???
>
>
> Are you setting the timing with the SPOUT connector pulled
> as it should be? The observation that the timing is jumping
> around a bit is typical of setting the timing with the SPOUT
> connector installed. You may want to thoroughly clean the
> MAF sensor if it has one to make sure it is reading the air
> intake correctly. I don't recall immediately whether the
> '95 460 was MAF or speed density but, I believe it was MAF
> controlled. There are instructions with photos in various
> places on the web. You may want to make sure you have the
> correct brand and heat range spark plugs installed. Many
> times, a plug of a different brand with the same heat range
> rating may actually operate in a different heat range than
> the same heat range designation of the recommended brand.
> Have you checked to make sure the engine is not running a
> bit on the feverish side. An increase of only 10 deg F or
> so above the recommended operating temp can easily cause
> this. An incorrect EGR flow will also cause this. You may
> want to replace the EGR control sensor. I don't know if
> yours has an EVP sensor or a DPF sensor. They do not
> always set a code. Also, pay close attention to the routing
> of the spark plug wires. Incorrect routing can sometimes
> result in crossfire under load. It is possible that a
> crossfire to another cylinder just stating the compression
> stroke can be the same a super advanced timing causing
> extreme pressures in the affected cylinders. The factory
> shop manual and some others will show a specific way in
> which the wires are to laid out and installed. This can be
> a PITA but, may be well worthy the effort. There have been
> TSB's to this effect over the years related to some Ford
> engines. Don't specifically recall that being the case with
> the 460.
>
> Good Luck
> Lugnut

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I dont know who you guys (or girls) are, but i just learned alot from
reading these two paragraphs. Some of what "lugnut" said was a bit over
my head, and my experince in Fords is little to none. But i just wanted
to say that i feel alright because i learned something...so...thanks!