99 tahoe broke down...help!

[SouthernHoe]

]My 99 tahoe has had what I thought to be some rocker arm noise. I pulled the passenger bank valve cover a month ago and turned the second one in about a quarter turn. That seemed to fix it. It was ran about 3 to 3.5 qts low when I found the remote oil filter lines leaking. Replaced and all has been well or so I thought. The last couple weeks the noise has come back with the cold weather. today I was driving down the road and it started to miss on a cylinder. I came back to the house and got a number 6 cylinder misfire code. I change the spark plugs, cap, rotor, button and wires. #6 was wet with fuel and all others looked good on burn. after all that I still have the miss. New plug is wet like the old one.


I tried to do a compression check and got 75 I think on that cylinder and 100 on the one behind it. This was coil wire off and turning it over at full throttle. I say I "think" 75 because it held once and then after that got only a bouncing needle while having someone else turn the engine over. I'm not a hundred percent sure my gauge is working right and I need to know where to go from here. Could this be in the head or valve train and not a piston/lower block issue? God I hope so. I'm just trying to make it through hunting season and ultimately get another year is out of it to pay off the wife's car and get something newer.


let me know where to go from here....this engine has about 60k on it.when we rebuilt it I replaced everything. ..heads...crank...pistons..rods....etc...etc..


The only other thing i can think to add is in addition to the tapping when starting cold i have heard what i can only describe as a metallic sound similar to an ac compressor clutch going out but it wasn't that. It was also on that passenger bank valve cover. I'm going to pull the valve cover tomorrow after work but wanted to check in first on what to look for.

 

[SunlitComet]

Have a leak down test performed and you will have your answer as to what general part is possibly leaking compression. Also a injector balance test as well. It will pinpoint a leaking injector which if it is so could cause some pinging. And be sure that the plug wire is fully seated. Mine fell off slightly and gave a ping effect in addition to the feel of a dropping cylinder.

---------- Post added at 08:56 PM ---------- Previous post was at 08:52 PM ----------

Might add that if your compression readings are correct you have a serious problem. Block replacement is required at 100 psi or lower. BTW what was the needle bouncing looking like?

 

[SouthernHoe]

ok here is where I'm at so far. I got a new compression gauge is mine failed I have a hundred and seventy five to 180 pounds on all cylinders except number 6. 6 is 32psi.

I then got the number 6 cylinder to top dead center on the compression stroke and pump air from my compressor into the spark plug hole. I had a little loss come through the crankcase out of the oil fill but most of it came through the exhaust pipe.


and then pulled the valve cover and found the rocker arm over that cylinder turn sideways not even touching the valve it had so much slack in it. I checked the push rod and the valve I and they look fine but when I slide the push rod down the center of the hall it's going way deep so I think there is a collapsed lifter.I'm going to pull the intake tomorrow to inspect the lifter journal and replace the lifter but I'm concerned about why the lifter failed so I feel like I may as well pull the head off and check for a burnt valve that may have stuck causing it to collapse.


comet do you think that's a good move? Have you seen lifters just fail? I also feel like it may be a burnt valve because the lifter doesn't explain my compression loss. If the valves burnt then the low oil from my recent oil leak may have caused that? Make sense? Thoughts?


edit sorry for the grammar I'm on my phone and greasy...lol

 

[ccapehartusarmyINF.(ret)]

the s10 i bought years ago that had to have the motor replaced after 9000 miles
had 170 to 180 on all cylinders except one had 60 psi
after like 500 miles right after an oil change id start it up and those lifters would clatter so bad i check the oil and it barely register on the dipstick

 

[SouthernHoe]

That's about how mine was when I found the leak...just a drop on the tip of the stick...took 3.5 quarts to full again.

 

[SunlitComet]

Lifters don't have a boat load of give in them. So make sure you are not just hitting rock bottom of the mounting it down part. Set up the engine for a valve adjustment. Align crank dampener timing marks and make sure both #1 valves are closed and not moving at all. That is tdc firing for #1. Now make one complete revolution of the crank. Inspect for obvious damage of lifter as best as possible and rod, rocker and so forth. Install them and tighten the rocker nut while spinning the rod around feeling for the lash resistance. When you feel resistance spinning the rod stop and for your issue just tighten it 1/4 turn. Put the valve cover back on and give it a test run and post the results here. If it seems better do another compression check. How does the engine sound? If the lifter collapsed and the valve was staying closed as a result there is generally no leakage past a closed valve. So no burnt valve. That happens when your valve does no fully close like a defective spring or the valve jamming in the guide somehow. Like tighten down the valve rocker way to much allowing the hot gases to leak thru the valve and seat. Start with that before yanking the intake.

---------- Post added at 02:06 AM ---------- Previous post was at 02:03 AM ----------

I have not seen a lifter just fail like that as the tolerances of the moving parts are very tight. It would have to be oil dry or the clearance severely damaged from lack of lubrication.

 

[SouthernHoe]

well I just got the intake off and that lifter was in pieces. In addition to that a lifter in a different cylinder was broken. I'm about to pull the rest of the lifters and that head I guess and see what is going on.

 

[SunlitComet]

Pics please.

 

[SouthernHoe]

---------- Post added at 10:19 PM ---------- Previous post was at 10:18 PM ----------

 

[99Vortec]

The lack of lubrication might have scorched your crankshaft rod/main bearings as well.

What was your oil pressure gauge reading prior to failure?