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Discussion Starter #42
Thanks. Yea I would like to hear from others. The reason I ask is I am going to try to figure out if a ring in bad on C1 before I assume it’s a valve... I am for removing the heads and have them rebuilt and a cam replacement $1K. Its 15 years old and worth it. However rings would mean an engine rebuild (right?) or new engine, and it’s not work investing $4-5K. I would just use it til it’s over...
 

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Discussion Starter #43
Ray I cant remember for sure but last November I think I did that. Something about if the compression improves a lot after a teaspoon of oil it’s a ring? I think my test did not change any with 170 psi before and after oil.. I am going to research that and do that again today...
 

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Stephen, 170 psi is not poor compression, in fact, it is very good compression.
Was the number a typo?
By the way, the compression should be done, when possible, with a warm engine, this let's the rings and valves expand.
 

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Discussion Starter #45
I just finished a compression test on C1. Engine was not hot but I had let it get to operating temp and turned it off. By the time I did the test temp was likely around 150.

ok pics attached.
First test after 7 cycles of starter I maxed at 190 psi...

Then I added a cap full of oil to cylinder and repeated test. After 7 cycles I maxed at 215 psi...

So what does this mean? Shoukd compression be cause of a misfire? Do I have a bad ring?
 

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Discussion Starter #46
Be aware that last November I tested all cylinders and all were around 200+ compression (except C1 was 170). I did add RESTORE to oil change in Summer but have flushed that since. May the restore has helped it go from 170 to 190?

Last November I also did a leak down and using 50psi reference and all leaked less than 10%. Of course it was very first time I had ever done a leak down. I set my TDC using the pressure gauge and turning the crankshaft until it peaked...

I am going to do the pressure test on cylinder 2 that is also having some misfires but not setting a code..
 

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Stephen, this question is in reference to the compression pics, which cylinder are you calling #1?

And, are you seeing the #1 (p0301) and the #2 (p0302) mis-fire codes?
 

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Discussion Starter #51
I know I am sharing a lot of info. So above C1 was 190 before oil, 215 after oil.

I just test #3 and #5 on same bank.

#3 before oil = 196 psi
#3 after oil = I skipped because it was very difficult to find the thread on this one when installing the pressure cable.

#5 before oil = (see pic) 190 psi
#5 after oil = (see pic) 210

Key takeaway. my #3 and #5 cylinders on same bank do not misfire. The compressions are similar and while the after oil increases #1 by 25 psi it also increased on #5 by 20 psi....

I am going to replace the injector next... but if not injector who votes it’s a ring , verses a bad valve /seat?
 

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I have never had any 302-308 codes ever!!
ok, sorry about asking about the cylinder numbering; but had to know we were on the same page.

Ok, question, above you say you haven't seen a 302; but earlier you thought #2 was misfiring; why are you saying that?

And, I think your compression is good on all cylinders.
 

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Discussion Starter #53
I am attaching the pic again off my scanner. It’s also in prior responses. If you look at pic at bottom I have windows built for Cylinders 1-8. in bottom left of screen are 1-3-5-7 (or bank 1), and bottom right of screen is 2-4-6-8 (or bank 2). The bottom row is history, the next row up is current. If you notice it’s cylinder 1 and 4 with counts... you may have to zoom in on pic to see window titles...

Also on screen at top I have a line graph for STFT and LTFT as well as decimal windows for each and a decimal window for O2 sensor.. again left side is bank 1, while right side is bank 2...
 

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Discussion Starter #54
I am attaching the pic again off my scanner. It’s also in prior responses. If you look at pic at bottom I have windows built for Cylinders 1-8. in bottom left of screen are 1-3-5-7 (or bank 1), and bottom right of screen is 2-4-6-8 (or bank 2). The bottom row is history, the next row up is current. If you notice it’s cylinder 1 and 4 with counts... you may have to zoom in on pic to see window titles...

Also on screen at top I have a line graph for STFT and LTFT as well as decimal windows for each and a decimal window for O2 sensor.. again left side is bank 1, while right side is bank 2...
 

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Discussion Starter #55
Sorry for duplicate msgs.. not sure how that happened. Overall C2 is not my concern at this time.. C1 is taking the most misfires...

Also just sharing (see pic) I did put this harness on each bank just to eliminate the coil pack wiring. There was no improvement.. so if it is wiring it’s from main bank connector back to computer..
 

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Discussion Starter #56
No worries ask me anything.. I need help... I never did swap injectors today since I was compression testing.. I will get that tester kit I ordered and see if all of the original injectors are working.. if so I will swap all back..

the history on this issue is 1 year ago I got an engine light P0300 code.. at that time I knew nothing and started with basics.. I ended up replacing injectors so I am pretty confident it’s not injectors...

so far it’s not.....

Vacuum - intake manifold rebuilt, MAP replaced, Throttle Body Replaced (this threw a code) MAF cleaned, smoke test passed, Fuel Evap solenoid replaced, tested with propene, tested with break cleaner... monitored STFT and LTFT during propene testing and no changes..

it’s not
Fuel - new fuel pump 2 weeks ago, pressure at spec, new fuel filter, new fuel regulator, new injectors. New o2 sensors just installed and fuel trims are good...

it’s not ignition - CAM sensor replaced 1 year ago when I did intake, just replaced CPS and added .030 shim, did relearn and this resolved the stall no crank problem.
In addition today I pulled the coil wiring connector off of C1 and then C2 at different times. After a few seconds each through a code P0351 or P0352 respectively... This tells me the wiring and signal between ECU and coil is good. I think...

It’s not compression - or well compression tests good...

I am a DYI guy learning as I go. My gut tells me the only thing remaining is leaking valves, cam lobe not opening valves far enough, bad ring (but how does it pass compression)......

or last but not least could I have a ECU that is having issues?
 

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With the compression numbers I've seen, the valves are fine.
Try a little valve cleaner in the gas.

Do you use tier one gas?

Ya know, in the old days carbon build up would give misfire, what octane are you using?
 

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Discussion Starter #58
I always use Shell regular. Never use anything else. Last year I ran Seafoam through fuel and intake throttle body. In spring I ran ACDelco Top of Engine cleaner through intake throttle body. I have also added liquid B12 in fuel....
 

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Discussion Starter #59
I think over spring break I am going to send the heads to shop. The HVAC compressor is bad and this would be a good time to go ahead and replace the cam and lifters. I will send new springs to shop for heads. I think the shop will replace any valves needing it and per my buddy they will pressure test the head so it’s like new.... this will be a fun project and cost me a $1K to do but if I am lucky it will not be a piston ring issue and I will have a damn good engine for a lot longer...
 

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I think you have a damn good engine right now.

You need to get a professional opinion before you tear that engine apart.
 
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