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Andrew_350 -> 91 silverado 350 preignition and detonation woes (9/9/2006 6:13:32 PM)
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OK, so I first bought this truck with an EGR problem which I fixed with a new valve and solenoid, passage cleaning etc. after that there were no more EGR codes and no more preignition.
Still had some spark knock under initial full throttle.
I recently put on headers and dual exhaust and now im getting the occasional code 32 EGR on the highway.
ive still got spark knock and preignition under light throttle. I do recognize that headers and duals can cause egr problems, and I do recognize that headers can sound like preignition.
However this preignition seems to happen in the same manner it did when I initially bought the truck.
The preignition (rattle) stays no matter what fuel i use, the spark knock almost goes away when i put in 94.
Ive had the truck to a shop and their scanners pick up the knock, blah blah, but they have no idea where its coming from.
So far, ive put in new plugs (the proper ac delco, proper gap) wires, cap, rotor, esc module, fuel filter, checked timing, egr valve works fine, when i apply vacuum the engine stalls as it should, fuel pressures good.
I cant think of any thing else and I'm all out of ideas any ideas as to what would cause this, and whether or not my preignition really is preignition or just headers would be greatly appreciated.
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