Engine knock [Archive] - GrandAmGT.com Forum

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el nino
01-24-2007, 07:18 PM
can u get engine knock from just simple mods like CAI and Exhaust?
i think my engine might have it but im not positive.

LoboMan7409
01-24-2007, 07:24 PM
No, the cause of engine knock is usually cheap gas, try a higher octane next time you empty out

el nino
01-24-2007, 07:33 PM
ohh i thought i read somewhere that modding could cause engine knock??
ill be sure to try higher octane next time. thanx.

bballr4567
01-24-2007, 08:19 PM
Are you sure its a knock??? Does it do it just when you are warming it up or all the time?

gectek
01-24-2007, 08:21 PM
wait a minute, there should be no cause to use higher octane on a stock engine with the stock tune. sometimes if the parts you put on increase the valvetrain noise, then it can induce false knock from the sensor. but there is no need to use higher octane than recommended by the manual, i.e. 86 i think, unless you have somethine wrong with ur engine. i have both intake and full ss headers/botla catback and i am even running the DHP PCM and i can run reg octane with no KR

as long as your engine is in good shape, there should be no knock

the best way to check for knock is with a scan tool, and then hit your block with a ball peen hammer right by the sensor to see if you can actually induce any knock signal, then look around and make sure that there isnt anything that could cause any false knock, you may be hearing lifter tick, piston slap or any other plagues that these engines are prone to

LoboMan7409
01-24-2007, 08:38 PM
well a lot of people mistake things like lifter tick and cold starting as knock

gectek
01-24-2007, 08:41 PM
true, thats why i suggest using a scan too to check for knock

bballr4567
01-24-2007, 08:44 PM
well a lot of people mistake things like lifter tick and cold starting as knock

Yea thats why I asked if it was just at start up and so on. Mine has the same thing but after its warmed up you cant hear it unless you have a steth.

gectek
01-24-2007, 08:45 PM
thats prob lifter tick then, it kind of diminishes with a warm engine

el nino
01-24-2007, 09:06 PM
well if it is lifter tick or pistons slap how can i eliminate those? or even determine it?

gectek
01-24-2007, 09:09 PM
well if it gets quieter when the engine warms up, or is more pronounced in cold weather, then goes away when it is warmed up, it is either of the 2 usually. piston slap i think will also occur if the engine is in P or D and idling, but dont quote me on that one 100%. use a steth to check the middle of the intake and if you hear ticks then it should be lifter tick

bballr4567
01-24-2007, 09:15 PM
Anyway either condition really isnt bad at all. Just kind of an annoyance.

gectek
01-24-2007, 09:17 PM
well, both are annoying, and can lead to bad engine probs, if the lifter breaks, or gets siezed in the bore, or a piston getting so worn it wont seal, or tearing the cyl walls up

bballr4567
01-24-2007, 09:19 PM
Well how often has that happened??

gectek
01-24-2007, 09:20 PM
to me...0 times, but to SBC's with bubba behind the wheel and running it 100k miles like that with the trailerhouse behind it....enough

bballr4567
01-24-2007, 09:22 PM
HAHAH yea my 01 has 141k miles on it and besides the lifter tick there is nothing wrong with it at all. Of course I replaced the LIM for the first time ever on the car at 135k. Other then reg maintance stuff the car has been great.

el nino
01-24-2007, 09:27 PM
well i guess ill find a steth somehwere and check it out. now that u mentioned the temperature outside.. in the summer when my car start and is ideling it will make a loud clanking noise but it will deminish when i turn the a/c on. i was told it could be some pump by somone a long time ago. any idea as to what that is?

williamGT
01-24-2007, 09:33 PM
most 3.4(3400SFI) has a piston slap mine was one of them. mine started at 8000KM....GM had to put 6 new piston in the engine. good luck

gectek
01-24-2007, 09:34 PM
maybe the pump that blows smoke up ur @$$, but i dont think it would be any other pump. does it happen all the time when you dont run the a/c...i would use the steth to find that also, could be idler pulley, or any pulley,

and i got u beat, my 02 has 173k mi on it and i replaced the LIM gasket at 168k mi. a faint lifter tick. ill be getting rid of that, when i upgrade to 3500 baby!!!

gectek
01-24-2007, 09:35 PM
well if you use pistons i would use the 04 and newer 3400 pistons, i think they are grafal or molyb coated IIRC, i think they are 99 a piece and include rod and pin

bballr4567
01-24-2007, 09:42 PM
SWEET!!! High mileage FTW!

When I was buying mine I actually called the first owners to confirm that they had put 88k miles in two and a half years and they said yup. lol

And nino the only thing that I can think of making the noise is the actual A/C. I had an older 3100 and it did that for a long time until finally the A/C just gave out.

gectek
01-24-2007, 09:43 PM
well the telltale for the a/c is usually grease slung all over the left side of the engine bay and all over the a/c comp and surrounding area

bballr4567
01-24-2007, 11:42 PM
Yup exactly. Its something on that side of the engine though if it only happens with the A/C off. At least that is what Im thinking.

gectek
01-24-2007, 11:51 PM
yah because it puts load on the bearings when the entire assy isnt moving