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Discussion Starter #1
it sounds like something its loose when i step on the gas after 4500 rpms but if i go easy on it it can go to red line with no noise at all. i check everything but i cant seen to find the problem. the engine its a y8block z6crank pm7pistons and rods d15b vtec head p28ecu never tune. was runing perfec for about 6 months. has any body had this problem before?
 

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Describe the noise. Is it high pitch rattle quite similar like you'd be frying bacon?
 

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Discussion Starter #8
all i get its 91 all the time, the noise its like a rattle. its like something gets loose rite before vtec kick in.
 

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Curious George
'99 LX Civic Sedan
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Hard to say without seeing it, but it looks like pinging.

Did you check the plugs these last days ? What color are they and does it have kind of aluminum pepper on them ?

What RPM your vtec must lock on ? You said around 4500rpm the noise come alive.

Does vtec has a mecanic engaging? if not engaging properly you might stay on vtec fuel and ignition table in ECU, with pm7 compression it's not really good. Vtec selenoid might have the signal but not engage, it won't give you cel.

Maybe it's not that, but it won't hurt to double check.
 

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Discussion Starter #12
well i try to get a video and post it tomorrow. well i put a vtec light just to see were it kicks in and its about 5600rpms but if i go wot it kicks in at 5000rpms. its stock p28ecu.
 

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Discussion Starter #13
well i have to go to work but i'll take a video and post it tomorrow thanx for the help.
 

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Curious George
'99 LX Civic Sedan
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well i try to get a video and post it tomorrow. well i put a vtec light just to see were it kicks in and its about 5600rpms but if i go wot it kicks in at 5000rpms. its stock p28ecu.
Sounds wicked 5000 to 5600 engagement...
 

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its like a high pitch rattle.
Sounds like a detonation. If you run PM7 pistons with Z6/D15B head, it'll get quite high compression ratio and stock ignition timing is too much. Try to retard the ignition somewhat (when looking to dizzy cap, turn the dizzy clockwise). If this cures the problem, detonation is your issue and you need to tune your ECU for modified engine. Do you run stock camshaft? If you do, I recommend you to get aftermarket one ASAP.

VTEC is supposed to engage at lower rpm when at WOT, and somewhat higher when not at WOT to achieve better fuel economy at higher cruising speeds. WOT engagement should be around 4500rpm in stock ECU, cruise engagement 5...5500rpm.

EDIT: Have you checked your valvetrain and lash?
 

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Curious George
'99 LX Civic Sedan
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Sounds like a detonation. If you run PM7 pistons with Z6/D15B head, it'll get quite high compression ratio and stock ignition timing is too much. Try to retard the ignition somewhat (when looking to dizzy cap, turn the dizzy clockwise). If this cures the problem, detonation is your issue and you need to tune your ECU for modified engine. Do you run stock camshaft? If you do, I recommend you to get aftermarket one ASAP.

VTEC is supposed to engage at lower rpm when at WOT, and somewhat higher when not at WOT to achieve better fuel economy at higher cruising speeds. WOT engagement should be around 4500rpm in stock ECU, cruise engagement 5...5500rpm.

EDIT: Have you checked your valvetrain and lash?
Sounds like I said before dude ? :p

But his car did run well, but not now. Something probably happened, not like always making this noise since begining.

Aftermarket camshaft will help if don't have vtec, it will drain all the power band pressure. Vtec first lobe doesn't drain cylinder pressure that much, it often like a stock cam.

PM7 pistons untuned, you're sitting on a grenade bomb. It will break, you don't know when, maybe something internal has broken.

Check the plugs it will tell you about detonation and mixture a bit, check vtec engagement, check the valve lash for loose valve or worst, bent valve.
 

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Curious George
'99 LX Civic Sedan
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Not about the valve lash, if a valve is bent perhaps. A bent valve can run rough normally, when at full throttle, it might have weird sound from engine.

It's a guess.
 
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