98 5.7 rough idle and stalls

[beedubleyew]

I just put it in to make it to work a few miles away, I have new ones coming tomorrow

so an update. I just found a piece of small spring under valve cover, turns out its from the valve stem seal on #6. still have 0 compression. I'm about to change the seal on exhaust and intake on 6, because I'm still having missing codes come up and rough idle.

 

[Road Trip]

Sir, you mentioned earlier that you don't have an oil consumption problem, so if I were
you I wouldn't go to all the effort to replace those valve stem seals. If your
thought process is that by changing those valve stem seals that your compression
in #6 will return, it won't. @Schurkey has been giving you proven-good
troubleshooting guidance.

Big picture:

1) Engine is missing, normal tune up items don't correct, mechanical
failure is suspect.

2) Compression test is performed to figure out which of the 8 cylinder(s) are bad.

3) The next step in the troubleshooting process is to perform a Leakdown
Test in order to further narrow the failure down to an intake valve, exhaust valve,
or the piston/rings within the cylinder that failed the compression test.
-0- psi means that the problem will not be subtle. Think burned exhaust valve,
bent intake valve, or holed piston.

And since the reading is -0-, you don't even need to get the test setup to
quantify exactly what percentage of leakage is happening. Instead, you need
to chuck up compressed air to the bad cylinder (at TDC on the compression
stroke) ...and then listen for lots of air escaping out of the exhaust pipe?
Or hissing out of the throttle body?

And if they are both quiet, then lots of air hissing from the oil fill opening. (By the way,
no excess oil consumption reported would tend to eliminate the piston/ring possibility.)

And the bent pushrod discovered would also lead me more towards one or more problems
with your valves.

****

I know that this is a rehash of what has already been shared w/you, but when
you mentioned that you were going after the valve stem seals on the bad cylinder,
I wanted to share the above & get you to do just a little more troubleshooting
first.

Let us know what you find. Thanks!

 

[Erik the Awful]

so an update. I just found a piece of small spring under valve cover, turns out its from the valve stem seal on #6.

I'm curious how that happened. Is the #6 valvespring damaged? Are you running the factory cam? (I can't remember if this has already been stated) Is there other FOD bouncing around in the top of the head?

 

[beedubleyew]

Sir, you mentioned earlier that you don't have an oil consumption problem, so if I were
you I wouldn't go to all the effort to replace those valve stem seals. If your
thought process is that by changing those valve stem seals that your compression
in #6 will return, it won't. @Schurkey has been giving you proven-good
troubleshooting guidance.

Big picture:

1) Engine is missing, normal tune up items don't correct, mechanical
failure is suspect.

2) Compression test is performed to figure out which of the 8 cylinder(s) are bad.

3) The next step in the troubleshooting process is to perform a Leakdown
Test in order to further narrow the failure down to an intake valve, exhaust valve,
or the piston/rings within the cylinder that failed the compression test.
-0- psi means that the problem will not be subtle. Think burned exhaust valve,
bent intake valve, or holed piston.

And since the reading is -0-, you don't even need to get the test setup to
quantify exactly what percentage of leakage is happening. Instead, you need
to chuck up compressed air to the bad cylinder (at TDC on the compression
stroke) ...and then listen for lots of air escaping out of the exhaust pipe?
Or hissing out of the throttle body?

And if they are both quiet, then lots of air hissing from the oil fill opening. (By the way,
no excess oil consumption reported would tend to eliminate the piston/ring possibility.)

And the bent pushrod discovered would also lead me more towards one or more problems
with your valves.

****

I know that this is a rehash of what has already been shared w/you, but when
you mentioned that you were going after the valve stems on the bad cylinder,
I wanted to share the above & get you to do just a little more troubleshooting
first.

Let us know what you find. Thanks!

Great info! I'm doing the compressed air in the sparkplug port a little later.

 

[beedubleyew]

so an update. I just found a piece of small spring under valve cover, turns out its from the valve stem seal on #6. still have 0 compression. I'm about to change the seal on exhaust and intake on 6, because I'm still having missing codes come up and rough idle.

I took the rocker arms off #6 and hooked air up to the spark plug port, air went right out the exhaust pipe. So I plan to take the head off next weekend starting Fri after work. I spent an hour or so working the valve with ATF up and down and around, at first it was stuck, now it's 90% free. Thanks for all the help!

 

[Road Trip]

Good job with your testing/troubleshooting -- plus sharing what you found!

Good look with the next phase -- taking the actionable info you have
obtained & starting with a focused repair.

Please continue to keep us in the loop. Good luck --