Ok so I headed to the old Auto Zone and rented their compression tool. To my surprise its brand new, just like the fuel pressure tester. The little shrader valve is clean and super smooth and easy to push.
On the evertough compression tool, the shrader valve was a lot more stiffer and harder to push in, hence the low compression readings.
Will re-test now.
Alvaroemg,
Outstanding follow through on the retest! I especially like your cross-checking of the
2 different compression test tools against each other. And what you discovered with
the schrader valves on the 2 different tools makes sense, is physical proof of Shrurkey's
commentary, and is a valuable example of how easy it is to grab a test tool and end up
with yet another variable instead of a calibrated constant to troubleshoot with. (!)
Good job.
We have compression!
Here, cleaned it up a lil bit. Results are after a few seconds(time it takes me to get down, and walk over to gauge)
#1 - 170
#2 - 165
#3 - 170
#4 - 175
#5 - 175
#6 - 165
#7 - 175
#8 - 165
Alright, we need spark, fuel, and compression in order to achieve reliable combustion.
Your compression test results are really good - I for one don't think that a follow-on leakdown test is warranted.
Since the #2 & #4 cylinders match the other 6, we can safely remove the 'dead hole' possibility out of the troubleshooting tree.
This leaves the ignition & fuel delivery systems. If reply #1 you mentioned that you have already updated the
spider with the Standard FJ504. For the moment I am going to
assume that all is well, and that you don't have
a leaky injector (mis)feeding the problem cylinder.
At the moment the biggest opportunity for improvement is obviously the ignition system. Thanks to your clear photos,
the cap and wires are showing obvious issues, and also replacing the rotor is common sense. Once you get all 8 plugs +
the other high voltage parts installed, I am looking forward to seeing how the engine/O2 sensors/VCM combo responds.
EDIT: I looked again at your fuel trims, and for the bank with the problem cylinders (#2 + #4 / Bank 2) I'm seeing that it's
leaning out long term, which would make sense given that you have replaced those plugs and lessened the false-lean misfires.
How about after your renew all the high voltage ignition bits that you disconnect the battery for 30 seconds so that anything
mislearned in the fuel trims up to this point is discarded, and we can start with factory fresh settings? Note: It may take a
bit of driving in order for the system to relearn, but this will help us rationalize your engine bay and help get it sorted out
quicker.
****
Speaking of which, I don't remember seeing any mention of O2 sensor maintenance in this thread/history leading up to the
cylinder head replacement? What is the current status? BTW, bummer that the neighbor 'lost' his good scanner, for it would
be really helpful if we could get an idea of the O2 crossing counts for the front left & right O2 sensors?
I mention this based upon the pictures of your spark plugs. It looks like you are running richer than expected?
NOTE: If you were experiencing ignition-related misfires, then each misfire sends lots of unburned oxygen past the O2
sensors, creating a 'false lean' being fed back to the VCM, which in turn is going to enrich the mixture in order to try to
get the O2 sensors toggling around stoich. In this case, the O2 sensors are the victims of the misfiring, not the perpetrators
of the too-dark plugs.
****
Big picture recap:
You've made some good troubleshooting progress. The mechanical side of things looks good given the compression test
results. And you avoided being led down the garden path with the 1st (inaccurate) compression test gauge.
You've done the right thing regarding checking your fuel delivery system pressure, and also replaced the original style
fuel injection with the redesigned part.
Currently the high voltage side of the ignition system is where you are currently focused on. Once that it put right, then
here's the possible scenarios we have to choose from:
* A) All misfires disappear. All 8 cylinders color anywhere from light tan to bone white. Problem solved, root cause was misfire-induced
too-rich A/F ratios via false-lean scenario. (And #4 cylinder had lost the ring seal due to cylinder wall washdown, but recovered.)
Plus, you check the CMP<>CKP 'Cam Retard' value, and it's within spec. Nothing let to do but relax and enjoy the ride.
* B) 7 out of 8 cylinders color good, including #2. Meanwhile, the #4 cylinder continues to prematurely oil foul the spark plug. Given
the good compression test, both valve and piston ring sealing is good. So the oil must be ingested from outside the cylinder?
If smoke test clears intake manifold leak (ie: sucking in oil from the lifter valley) then the only remaining source of excess oil would
be an intake valve stem seal that was damaged during cylinder head assembly?
* C) No ignition misfiring detected, but the plugs still color darker than expected? Cross counts of O2 sensors checked,
deemed lazy, and new O2 sensors fix plug coloring/improve drivability/minor improvement in MPG.
****
The bottom line is that once we minimize all the variables with the ignition, I really want to see where the engine takes us.
My fingers are crossed that all 8 cylinders straighten up and fly right. On the other hand, if 7 of the 8 cylinders end up
running clean, then we will need to focus on the outlier (#4?) and see what it will take to get that plug to quit fouling out.
I know that this is a lot to wade through, but hopefully you can see the stepping-stone approach, and also that you are
making good troubleshooting progress. It seems that you have been working through a handful of overlapping issues
on this motor, but it looks to me like you have some solid mechanical compression as a foundation to build upon.
Keep fighting the good fight. And let us know what you discover after the ignition system renewal.
Cheers --
But could you elaborate on the compression ratio comment? I guess I don’t understand how a pressure can dictate a volume
