Bad compression numbers

[boost97gst]

Up to date mods in list.

Ever since i got link ive had intermittent cylinder 2 or 3 misfires. At idle it would go really lean. Like an injector problem. Brand new ptes. Well i checked and then checked and checked again ever god damn wire for the injectors and its all good.

I dont know what to blame yet: The ecu injector driver or the machinist or just bad luck with my rings. Ive never seen more than 3 degrees of knockret, i run conservative timing. engine is 5k miles old. Stock CR pistons.

Checked it tonight and got from 1-4 : 162,90,165,165.
Cylinder 2 is ####ed. I cant believe this. Going to wet test it tomorrow. Def not a hg, its either the rings or the exh valves.

Weird thing is, ive pulled the plugs a million times and theyre ll the same shade of color. None stood out as lean or rich. The machinist fd it up the first time and it started knocking at 300 miles, bone stock boost, ecu, injectors etc....
He admitted he reused the crank and it may have been out of spec(???). New crank and 5k miles later i have a busted engine. There may be a slight chance its in the valve train but i seriously doubt it.

Any clues as to what i should test for and in what order before i decide to send the whole thing in to JAM or just need valve work?

Thanks. Im in ####ing shock still.

 

[slickers111]

You gotta find out if youre losing compression from the rings, or valves, and go from there.

 

[BogusSVO]

Yes, a leakdown test is the next step.

If the valves fail the leakdown test, pull the followers off , one side at a time, and leak down again.

 

[boost97gst]

Would i notice a lean plug on cylinder 2? Or would it have turned back to normal by the time i got home and had idle time? I know the best way to read the plugs is WOT pull , during it shut engine off, coast and pull the plugs. I never did that unfortunately. If its the valves ill be so fn happy, then again, if theyre burnt then the piston is most likely pitted and melted a bit right? I never noticed valve train noise, only on the very first start up 5k miles ago.

Bogus, please explain. Im ignorant of valve terms. Youre saying put the leak down tester on and remove the follower on the intakes, then the exhausts? or vice versa? Im confused. Sorry

 

[BogusSVO]

That basically it, one pair then the other, the order will not matter.

This will help narrow it to a few things if it is in the head.

leak down Valves fail ( we will say you heard the air escape from the tail pipe)

Remove the exhaust followers.

Leak down test fail = yes then you know it is a valve sealing issues

Leak down test= pass now you know it is not a seat issue.
now bleed down the HLAs and install followers,
leak down = pass the HLA were not bleed properly
leak down = fail, valve tip height needs to be checked, also cam base circle if you have aftermarket cams.

Do you understand what I am trying to get you to do?

 

[boost97gst]

Yes. Absolutely. Makes sense , logical trouble shooting path.

One more thing, ive had people follow me and even during pulls there was never any smoke from exhaust. Idle, cruise, or wot. Rings usually do that. Just thinking about that makes me lean towards it being a valve problem.

Google helped alot. Heading to harbor freight first thing for a leak down tester. Fingers crossed guys, hope for a valve problem.


********UPDATE********

Did the test wet. Cold engine. cyl 1: 150 cyl 3: 185 cyl4: 185

Cyl2 i first used 3ml of oil. This should be plenty and is comparable to atleast a tablespoon if not more.
Results: went from 90 to 100. Not the gain i was looking for if it were a ring.
Next i used 6mls of oil in cyl2. Results: 120



After cranking over for awhile and checking other cylinders i went back to it when it had dried a bit, im guessing, and it read below 90. Iirc, ~80.

So to sum up: The guy holding the gauge last night must not have got an accurate reading on cylinder 1

Cyl 1: out of spec
cyl 2: WAY out of spec and well below service limit. Head and block both need to be disassembled.
I dont think a leak down test is necessary. Its just going to tell me what i already know.

So..... JAM for a shortblock and have them do my head as well? Bogus, whats ## thoughts? Did i screw up? btw, with a flashlight all 4 cylinders looked identical in color. Grayish brown. Looked like there was a bit of carbon deposit on all 4. I cant see everything without pulling the head and i wont do that without pulling the entire engine. Its coming out anyway.

Should i wet tewst again after i warm the engine up to op temps? Not sure if that changes anything as far as im concerned with the whole longblock needing work...



Edit 2: Hot test. IDK what the guy reading the gauge was seeing.... Hot test 1: 175 2: 110(??) 3: 180 4:180
With 3ml oil in number 2 it went to 120. Valves

 

[boost97gst]

Edit number: who knows.

Leak down test: cyl 2: 30% after 5 minutes. Bad rings. Tested cylinder 1 just for shits n grins. After 5 mins it topped out at 5%, past rings as well. Engine was warm.

Thank you to Bogus for all the help via PM. He truly is the man. Great guy. Ill start a new thread w plenty of pics when i eventually tear this down. Im off to go look at and possibly buy a 95 awd auto gsx. Cant stop now!

 

[boost97gst]

Picking the 95 gsx auto up today. gonna get cracking after surgery in november.
Let me just say something so it comes up in google search Precision engine precision machine shop Don at precision Go FU(K yourself pal. Twice i was bit by this snake. Very very costly and a heartbreaker.

he seems like the nicest guy, and he really is but damn that old dude cant touch imports or any 4 cylinder forced induction engine. His honing or crosshatching most likely caused my failure. Im too conservative with my tune. And all 3 of the other cylinders are fine. Dude sucks. Hes in Glen Carbon,IL Stay away.

 

[jhicks92]

Full leak down test. my .02 cents

edit: sorry didnt fully read the rest of the replies. sounds like this advice has been given.

 

[boost97gst]

^^^ Answers up 2 posts. Leakdown performed

 

[Bmx and Dsms]

Would the car still crank if you get 90psi from all four cylinders ? Because I just got new rings and pistons and its reading that I did use an Autozone gauge and I have not done a leak test(yet)?

 

[boost97gst]

Yes, it would crank of course. It would crank faster if it had 90 on all 4 . Thnk about it.
Does your gauge have a pressure relief valve? Did you crank it over at least 5 revolutions or until the gauge wouldnt read any higher? If thats so then you need a leak down and since all 4 are off i would expect you are off a few teeth on your timing belt. If its the rings one or two will really stand out as being low(usually, not always).
Just do a leak down on each cylinder at tdc of the compression stroke. Pop valve cover so you can see that your valves are closed on that cylinder and stick a long screwdriver down to make sure its at TDC..


Off topic: Got the 95 gsx today!!!! Lucked out already: havent opened the ecu but the ser # begins with an "E". Popped it open to be sure EPROM BABY!!!

 

[Bmx and Dsms]

But strange thing is that it doesn't crank even with 3 cylinders on 90 well it cranks but doesn't start all I hear is whining, then the intake manifold gets really hot in a matter of two or three tries(don't know if that's normal)

 

[boost97gst]

You may need to start a thread and make sure to communicate things a little better.