replacing MAF fixed it. tried cleaning again yesterday and got better
results that lasted 1 day. so I replaced it today, no knock, more power, and
I expect it will slightly help mileage.
as far as gas, all brands and grades were doing it and this horsie runs a
lot. that's why I was so concerned about the knock. the knock started about
a year after I got the vehicle so I had a baseline to work from there.
when I had replaced intake I checked egr passages on old manifold and they
were clean, so of course new one was. I used that to rule out the egr
system. I changed plugs about 3 months ago and even with 50K on them
(original per previous (initial) owner) so I had to guess (correctly
luckily) that chamber was not in to bad shape as far as carbon. previous
owner also got into it at least once a week. I had checked with the dealer
that services local sheriff vehicles, they are all 99 and up and had knock
sensors, I figured I could not use anything from them as a baseline.
I had suspected MAF was the problem but I needed to rule out the other 5 or
6 systems that could also affect this, the biggest obstacle was determining
if it was supposed to have the knock sensor or not.
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