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3.4 DOHC is knocking bad!!


bigdman

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93 DOHC has got a knock that sounds like its in the top end, like maybe a lifter or an injector? it increases with rpm but its not a steady rythm, its kinda sloppy sounding, but the car also runs slightly rough at idle. i have a feeling its close to the end for my DOHC? y/n but if so then it's time for an L67 to go in there. just wondering if anyone has had the same problem, any input is greatly appreciated :biggrin:

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Well is it more of a tick or a knock? If it's from the top end the only thing it could really be is a lifter. It could also be worn out fuel injectors. Because you have PFI and they fire at the same time it could be mistaken for an engine tick. You should get a stethescope and work your way around the cam carriers and see if you hear a lifter.

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run some lucas in your oil and see if it helps at all. i know for a while I had one really stubborn lifter (just one, always the same one) and I'd occasionally put a bit of lucas in and by the next day the tick would be gone. that was kinda odd though, since i think that lifter was gummed up from the swap

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well i just changed the upper and lower intake gaskets which gave me a chance to check out the lifters but i have always used lucas in my cars i am currently using a bosch oil filter, 4 qts of valvoline 10w30, and one qt of lucas still ticks, when i get a battery for my multimeter i will check the cps, on my 89 cutty the cps went out and it would not even start.

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not sure about the pre 95 engines, but from my experience 96-97 motors run hot and will benifit from a colder spark plug. not sure about thr part# for AC delco plugs, but the normal 96 plug under autolite is ap605 one range colder is a 104 and two is a 103. with my tuner i am runing a good deal of spark advance so i went to the 103's. i was runing NGK iridiums in the stock range before and i was fighting about 2-5degrees of engine knock at WOT. (have a scaner) now with these plugs im runing slightly more spark advance and even leaner A/F mixes and not a peep of knock.

 

basicly what im saying is if your plugs consistantly look to be runing hot drop a heat range. but from the sound of it this is ticking and not ping/engine knock. also even on a 96-97 motor, if your getting valve slap from the piston you wouldnt be hearing it for very long before something breaks

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