knocking problem

[mannsvillain]

I have a '97 Z71, I have changed the anti-knock sensor and always use higher octane fuel, but the knocking continues on acceleration. Any ideas?

[1997chevy454]

i have heard that floated lifters knock

[Butch 02 Denali]

Probably carbon buildup on the pistons. Try Seafoam, it works wonders to loosten and blow out all that nasty carbon build-up.

[Busted Knuckles]

^^^^ I agree. There should actually be no reason to have to run higher octane fuel. I just rebuilt the Vortec engine in my '99 Burb. We zero decked the block and I'm running flat top/4VR pistons. I fill up with the lowest octane gas available and it's never knocked, even under a hard load. Sounds like you either have oil making it's way into the combustion chamber or have a lot of carbon build-up on the pistons or in the chamber. If you can't find Seafoam, get a mister bottle full of water and spray into the throttle body at about 1500rpm's. It will load down a bit but it can sure make a difference. Good luck, keep us posted.

[mannsvillain]

Thanks for the suggestion Butch, happy to give it a try, can you pick up seafoam at most auto part stores?

[Cheyenne'88]

Yes, it's at most auto stores.
You could also try colder sparkplugs, a lower temperature thermostat, some of that coolant additive that cools more. (water wetter?) If you could advance timing a bit, and lower the intake air temp, that would help.
Is it a TPI? (I don't know newer trucks) Try running an injector cleaner.

[mgrotel]

what about ticking? or is that kinda the same thing?

[Cheyenne'88]

what about ticking? or is that kinda the same thing?

Broken bolt on the exaust manifold, maybe?

[FordeatinZ71]

no, it's not TPI, it should be SFI (Sequential Fuel Injection)

Josh

[98GreenMachine]

I have a '97 Z71, I have changed the anti-knock sensor and always use higher octane fuel, but the knocking continues on acceleration. Any ideas?

Are you sure its a ping your hearing? Not lifter tick, or a bearing knocking?

[98GreenMachine]

Is it a TPI? (I don't know newer trucks)

Just some info for ya:

88-95 used Throttle Body Injection (TBI)
96-99 used Central Sequential Fuel Injection (CSFI, Central SFI)

Tuned Port Injection (TPI) started in 85 with Camaros/Corvettes, but never a fullsize.

[mgrotel]

is it a really bad sign if my lifters are ticking somewhat loud?

[98GreenMachine]

is it a really bad sign if my lifters are ticking somewhat loud?

depends, are you sure its the lifters themselves or is it just loose rocker arms? If there has always been a noise, it may be rocker arms. If it has been quiet then just started ticking recently, it could be lifters.

Have you ever adjusted your rockers?

[mgrotel]

depends, are you sure its the lifters themselves or is it just loose rocker arms? If there has always been a noise, it may be rocker arms. If it has been quiet then just started ticking recently, it could be lifters.

Have you ever adjusted your rockers?

have never adjusted my rockers, the last couple weeks i heard the ticking at startup but afer a couple seconds it went away, today i started it and the ticking didnt go away so shut it off. came back later and started it again and the ticking trailed off as it ran but i think it was still there.

[98GreenMachine]

have never adjusted my rockers, the last couple weeks i heard the ticking at startup but afer a couple seconds it went away, today i started it and the ticking didnt go away so shut it off. came back later and started it again and the ticking trailed off as it ran but i think it was still there.

sounds like a sticking lifter. Try dumping a can of Seafoam or Marvel Mystery Oil in the oil and drive it for 15-20 minutes before you change it next time. It wont hurt anything, but it has been known to free a sticky lifter.

[mgrotel]

thanks man, it actually hasnt done it the rest of the day, but im due for some seafoam anyway, sorry to threadjack

[mgrotel]

i guess its still ticking, the longer i let it set with the engine off, the longer the ticking lasts when i turn it on, its pretty loud. whats next? replace lifters?

edit: ive already added half a can of seafoam to the crankcase

[98GreenMachine]

i guess its still ticking, the longer i let it set with the engine off, the longer the ticking lasts when i turn it on, its pretty loud. whats next? replace lifters?

edit: ive already added half a can of seafoam to the crankcase

Yes, pretty much the only way to positively cure this is to replace the bad lifter. Unfortunately this involves pulling the intake manifold off. You don't have to replace all 16 lifters, only the ones that are bad.

[mgrotel]

would you suggest a general rebuild while its open? 214k miles

[mgrotel]

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