99 Chevy tahoe is Tapping and high pressure

[schube1255]

I need some advice,
my tahoe drank some bad delaware gas and I havent serviced it in a while. It was running really rough and throwing codes. po300 - po 305 - po 172 - po175 - and oxygen sensor on cat. was bad.
I installed:
distributor cap and rotor -
new spark wire set -
new spark plugs -
oil change -

still ran like shit - rough idle and pressure changes
I took it to a mech and he said it was the fuel injector.

I replaced the fuel injector and fuel pressure sensor. lots of carbon buildup

Now it is tapping loud - but runs good - I did a compression test and read 190psi on 7 cylinder and 150 on #2 but it runs good just taps really loud and the tap isnt going away.
I pulled the valve cover and tested the pushrods and all looks good.
I dumped in a can of seafoam and it seems to be running good , It just taps or knocks really loud.
Any help would be greatly appreciated.

 

[SunlitComet]

can you give the pressure reading of the other cylinders as well please.

---------- Post added at 02:46 PM ---------- Previous post was at 02:42 PM ----------

Your truck is running really rich. What brand and # of part did you use to replace the fuel injection spider and what fuel sensor are you referring to? Also names and # of parts you have done already?

 

[schube1255]

all 7 cyliders are reading 190 psi #2 is at 150psi

I used AC delco parts but the injector is made by GB injectors - it is OEM part

 

[SunlitComet]

Cylinder #2 is below the 20% variation allow between the highest and lowest pressure and that need to be addressed. #2 valve may be burned or may be leaking a little from some of that carbon build up. How did you do your seafoam and how much exuast smoke did you get from it. Can you be sure the noise is not from a bearing or rod? What was the condition of your spark plugs when replaced?

 

[schube1255]

I put i can, about 12 oz. into gas and some seafoam spray into throttle body - while running - very little smoke - brand new gapped at .060 plugs

 

[SunlitComet]

I was asking about the plugs that were placed. And again can you be sure the noise is not from a bearing or rod? Is it possible to get a audio or video clip of it?

 

[retorq]

Pull a plug wire one by one while the engine is running, if the knock goes away then it's something wrong with that cylinder ...

 

[schube1255]

Thank you so much for the advise -I am going to try the pull the plug wire trick, and I will shoot some video of the engine -

This one has got me - really all I did was replace the spider injector - it was not tapping before ,just runnin like chit. Now it runs great but sounds like a diesel tap. I used a homemade scope and cannot pinpoint where the noise is coming from -but it is pretty loud.

I also have a computer plugged into the truck and everything shows perfect, no codes - everything working ?

 

[retorq]

Flywheel to converter bolt??

 

[BattelWagun]

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.