99 Chevy tahoe is Tapping and high pressure

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SunlitComet

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If the noise goes away when you remove a plug like retorq said that would be a rod knocking at your door.

---------- Post added at 11:31 AM ---------- Previous post was at 11:28 AM ----------

That's more of a rattle though, but always a possibility.

I'm thinking its carbon buildup from that bad gas causing a valve not to seal properly.

I have had a tranny bolt do that too.
 
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schube1255

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Here is a picture and video of my 99 Chevy ***** 120000 mi


t99.jpg

Click the link for the video - its louder on the vid than in real time

http://s126.photobucket.com/albums/p105/eezzeee/?action=view&current=100_0799.mp4

---------- Post added at 02:41 PM ---------- Previous post was at 02:35 PM ----------

Here is a video of my 99 Chevy ***** 120000mi - click link - it is louder on the vid than in real time
 

ezdaar

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Tapping is more than likely a deqd or stickng lifter.
I will share a old school trick that was used long before any cleaning chemicals was avalible.
Trans fluid, get yourself a shotglass, have engine fully warmed up.
Pour one shot of trans fluid into oil fill, let idle for 15 mins.
If it doesnt go away or start to change volume, pour in second shot.
Listen carefully for changes! By se ond 15 min idle if. Noise doesnt go away, let it sit over night.
Fire it up and let warm up. Noise should be gone completly.
If not its dead lifter, bent pushrod or rod knock.
Regaurdless, change oil.
To check for bent push rod. Pull one at a time, clean it with steel wool then roll it on glass, if it wobbles. Replace it. Also that lifter is suspicious.
Write anything you fi. Down and check them all.

You can start on your low compression cylinder, as its suspicious alrdy.

Btw, after running the trans fluid, recheck compression. You may find its higher than the initial 150, as comperssii. Rings do stick due to carbon fouling.
Pouring a shot of trans fluid directly into that cyclnders spark plug hole, and lettng soak over night is best method of freeing stuck rings.
then while plug is out and coil unpluged, crank motor over untill no more trans fluid sprays out of plug hole.

You will want to change oil after these methods as trans fluid is a bigtime detergant and will eat up all oil sludge, carbon etc. But will ruin the oil.

Back in tye day we would pour in almost a quart of tranny fluid to clean out severly gunked up engines, even would pou it down the carb throat to clean valves.
Just now days with everyone going green and a million types of cleaners. The old but best methods are forgotten.

GL on tracking that noise down.

---------- Post added at 02:06 PM ---------- Previous post was at 02:05 PM ----------

Btw, i typed all that on my iphone.
 

SunlitComet

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valve train buddy.

you may have to reinspect them all and perehaps remove the heads if you can't see anything with a boroscope thru the plug holes.
 
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schube1255

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Thanks - I was told that tranny fuild might work but I was worried about the detergent .
I will give it a shot.

EzDAAR - I hope you were driving while textin that
 

ezdaar

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O I certainly was!
Was on freeway doing 90! and putting on my eyeliner!

Do both the trans fluid in oil and trans in cylinder back to back so you only change oil once, and it lets the detergeants work longer in oil.
 
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schube1255

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Well - I tried the tranny fluid in the oil trick and it worked ok but did not rid the noise.
It is a lot better, but when I give it gas it taps.
All of the lifters and rods look like new - the comp. test now is 150 psi at all cylinders
and it runs and drives good. It just taps or knocks.
I did notice a missing screw tab ( made of metal ) inside the plenum . and previous work done.
maybe it shot through and bent a valve. I really cant pinpoint the knock yet, and really dont know how to replacevalves and such.
 

retorq

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Replacing the valves is easy but you gotta be careful and you have to have the right tools.

I had a screw in stud loosen up on me, sounded a little like that. Did you check your rocker arms to make sure none were loose??
 
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schube1255

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Thanks for all the help -
but I need a little more advice..

If by some chance the new fuel injector was numbered wrong or if I crossed the injectors would it run - what would it do??
I mean like when I installed the new injector - if by mistake I put 6 into 8 and 8 into six --- or 5 into seven. ??? would it run ???
the injector was numbered and the manifold was numbered 1 - 8 I dont think I messed them up but I did rush.


I took it out for a spin today - it ran awesome - uphill, down all over runs great , but it still taps on idle - when i get to about 30 mph I cant hear any noise at all , like its perfect. but when I take off it taps. - the tap has quieted down but is still there.
 

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