Compresion Issues, Long Post

Gravy · 09-12-2006

I've run into compresion issues on a car. I know most of you will say "Rebuild that shi±!" But, i don't have the time, or the money atm to rebuild, and i'm seeing if i can fix the problem simply.

Symptoms are as follows. About 2 months ago when i first got the car i had 150-150-145-150 compresion. NO issues and the car was ok. Then randomly i get intermitent acceleration issues. Figured i have two studs missing, it's an exauhst leak and i'm sometimes leaking and sometimes not. New gasket and fixed the studs... Notice better spool up from port job, boost spike is fixed and no more creeping. Problem fixed? Thought so.

Five nights ago i give the car a compresion test to check and see what i'm running. First test: 150-152-130-150. Blown ring is my first impresion, i'm pissed and worried as hell i've gota rebuild over the winter. I go to remove the insert and hose from the head and see it's lose. I get a 145 and think, good, everythings still ok. Three nights ago the car starts idling rough and smoking while at idle but not under WOT or even partial throtle. I check the car again: 150-152-135-150 Figure i'll run out the tank of gas, then garage it too check it out and see what needs to be done. The next day on the way to work, idle's fine. No stubling at idle(Idle surge) and no smoke coming from the exauhst at idle, PT or WOT. Checked the compresion and got the following: 150-150-145-150

Today runs fine for about 2-3 hours worth of driving then part way through the day it's like a switch is turned off in the car. Runs like shit. Smoke at idle, rough idle and surging on me like mad. Tonight i check the compresion: 152-150-120-150

From what i've read and heard, with a "Variable" compresion PSI like this it wouldn't be a ring, once it goes bad it's bad. There's no good days and bad days. When i pulled the plugs i shined a light down the holes the last two times when i got the 145 and when i got the 120. When i got 145 PSI the top of the piston looked clean enough to eat off of. When i checked it on the 120 night there was oil drops on the top that i could see.

Sorry for such a long post, but i wanted all the facts in before i expect detailed answers or opinions. My question is, and this has been mentioned before when i was burning oil. Could it be a valve guide seal gone bad?

I pulled the manifold off tonight to install a new one on, and figure i'll hold off before putting it back on. But can't you replace the valve guides without having to remove the head? I can get access to a spring compresser for free, and damn near any other tool through a buddy at work.

Thanks in advance for reading this, and any replys i get back.

s1ngletracker · 09-12-2006

is there any oil in the exhaust port while you have the exhaust manifold off? Also, when you do a compression test and that cylinder is lower, put a teaspoon of oil in the cylinder and try again. If your compression goes up, its your rings.

**Shane@DBPerformance** · 09-12-2006

DSMs have dished pistons that hold puddles of oil, if you pour oil into the cylinder, it probably won't even make it's way to the rings and the compression will go up because you increased the compression ratio with the oil.

JiggahMan · 09-12-2006

It may also be a bad compression gauge. However, if it does turn out bad rebuilds really aren't that much. And I'm sure someone on here, other than a shop, would be more than happy to do it for your for fairly cheap.

niterydr · 09-12-2006

I would bet it is head related. Valve seal, carbon deposits, etc.
Like single said, check to see if there is oil in the ports when you pull the exhaust mani.
Shane is right, good luck doing a "wet" compression test on a dished piston.

b00stcreep21 · 09-12-2006

leakdown test the motor, and go from there. Broken ringlands can make a motor act funny sometimes as well. when mine went, i thought the valve seals were toast. It would burn a shitload of oil one day, then be fine the next. But when i pulled em out, and the piston fell apart, it was a little more obvious. I never compression tested mine though

Jakey · 09-12-2006

Quote:

Originally Posted by niterydr

Valve seal

It has always been my understanding that valve stem seal issues do not surface in a compession test, only in a leakdown test?

niterydr · 09-12-2006

Quote:

Originally Posted by Jakey

It has always been my understanding that valve stem seal issues do not surface in a compession test, only in a leakdown test?

Valve seal for burning oil/creating carbon possible that could be hangin up a valve.
It doesn't actually have anything to do in regards to a low compression cylinder, but it could effect the combustion chamber if it is poluting the system with oil.
I would be its more of valve SEATS or a cracked piston.

Pimpin Dsmstyle · 09-12-2006

My buddies car had the same shit happen in #2 cylinder when his ring land was cracked. Might not be pertinant to your situation, but it had the same symptoms.

tim · 09-12-2006

Are all conditions the same when you do your tests? Engine warm or cold, throttle all the way open, etc..

Have you tried a leakdown test or atleast tried a different compression tester? Leakdown would definitely be my next step.

Gravy · 09-12-2006

I've got a few things to answer, so bear with me if i forget an answer.

When looking at all of the exahst runners #2 and 4 are very clean, only small amounts of black soot as i'd call it, but no build ups. One was bad due to an exauhst leak, and actually got oil dripping into it once or twice, so there was a larger deposit around the outside, but the insides and the exauhst mani it's self was clean. #3, or the problem child as i'm starting to think of it, was horrible. There were actually resting deposits of soot or black powder in the runner and when looking up into the valves, it was coated black. Almost like there was a never ending hole. Anyways, the coolant lvl's are fine, and i'm getting no bubles coming out of the system when i pull the radiator cap when it's running. Both warm and cold.

Compresions were done on a mix of conditions. All tests were done in neutral(of course) on level ground by simply pushing on the starter button. Every time the engine was cold but the last time i did it with the 145 reading, but the plugs were still cool enough i could touch them by hand and it wasn't very hot. Otherwise the car had sat for 4+ hours and was just above room temp or cold. Not anywhere near operating temp.

Also, something i though of that's starting to scare me. WHen i look down the piston when there's good compresion the top of the piston looks new, shiny and clean. But when i'm getting shity compresion it's got oil on the piston. Shouldn't that burn on a little bit? I find it odd that it's nice and shiny. Don't recall the other pistons being dirty or clean.

Would a possible valve guide cause similar issues? I've yet to re-build an engine and doing so alone will be interesting to say the least. I've pulled a motor and removed the head once before. With our cars, can you remove the pistons, aka do a rebuild with the engine still in the car? I know on the old Escort you could pull the pan and remove them that way. Just getting them back in there was a bit harder(from the top of course).

Compresion tester is good. If i was getting f'd up readings on other cylinders i'd think it was bad. But getting no more then 2 PSI difference on all of the other 3 i'd think it's a good tester. The tester himself may not be the smartest one around, but it was done the same every time with similar issues.

Is a leak down tester something you get from a parts store or make yourself? I'll do some research tomorow and look more into this. But for now still fishing for some ideas and your input. Thanks for all the information and helpful ideas.

b00stcreep21 · 09-12-2006

do a hot compression test and see what you come up w/

tim · 09-12-2006

Quote:

Originally Posted by Gravy

Is a leak down tester something you get from a parts store or make yourself? I'll do some research tomorow and look more into this. But for now still fishing for some ideas and your input. Thanks for all the information and helpful ideas.

A leak down tester is a gauge set that allows you to pressurize a cylinder and look for leaks. It allows in say 100psi and you see how much it leaks down, say 20psi. Then you would have 20% leakage.

The nice thing about it is you can listen/look for leaks. If there is air coming out the tb you might have a bad intake valve/seat/spring. If you hear air coming out the exhaust you know it is a burnt exhaust valve seat/spring etc. If you take off the radiator cap and see bubbles then probably a headgasket.

A great tool for internal diagnosis, you do however need a decent air compressor.

I bought this el cheapo off ebay. Works well. There are some buy it nows if you dont want to bid. Otherwise I am sure LSE or DB or MAP could do it for you cheap.
http://cgi.ebay.com/ebaymotors/U-S-G...QQcmdZViewItem

Gravy · 09-13-2006

Can't do a warm comp test atm, exauhst mani is off for the new one, gasket is en-Rout and valve cover is off. Tomorow i'm going to set the engine to TDC and look around a bit to see what i find out, and where to go from there. Gona finish preping the exauhst

Thanks for the post, i have a 80 gallon tank of air compressed at 120 psi in the garage, so i should be good for a leak down test. I'll check to see if work has one tomorow, if they do i can rent it for free. If it's a bad ring//piston how can you tell it's leaking then? Losing presure with no sign of where it's going?

b00stcreep21 · 09-13-2006

you're not going to get consistant compression test results with the engine cold. same with the leakdown test. get ur exhaust mani back on, throw on the valve cover, and warm that baby up

joem · 09-13-2006

Bad plug wire or plug? Washing the walls of the cylinder with gas dropping compression?
Joe

Gravy · 09-13-2006

I've switch plugs, but i fail to see how the gas would drop compresion. I could see it raising the compresion, but not droping it. I think i'm going to put everything back together and try taking the car for a spin. Warm it up and check compresion, and hopefully a leak down test *Crosses Fingers*.

Also, no gas smell to the oil, or layer of liquid on top of the dip stick.

I've had plug wire issues with that cylinder for a while, had to get new wires because the #3 wasn't carying a spark about 3 weeks ago, new plugs less then a week ago.

s1ngletracker · 09-13-2006

Quote:

Originally Posted by ecoli

DSMs have dished pistons that hold puddles of oil, if you pour oil into the cylinder, it probably won't even make it's way to the rings and the compression will go up because you increased the compression ratio with the oil.

OK, nevermind that then!

I'm used to hondas

joem · 09-13-2006

If you soak the engines wall with gas compression can slip pass the rings.
Joe

s1ngletracker · 09-13-2006

Quote:

Originally Posted by joem

If you soak the engines wall with gas compression can slip pass the rings.
Joe

...not to mention cause accelerated wear on your cylinder walls from the lack of the coat of oil on the cylinders... causing permanent damage and loss of compression, and increased oil consumption.