Well, I've been having problems with this cheap used motor I put in my Eclipse. Its been stuttering at idle and low RPMs, but upper RPMs its fine. I've changed all the usual stuff: plugs, wires, coil, fuel filter, pcv, cam and crank senser, good timing, no vacuum leaks, etc. Well I did a compression test and heres how it turned out:
Cylinder #1: 200
Cylinder #2: 200
Cylinder #3: 10
Cylinder #4: 200

My number 3 cylinder is dead. I suspect a valve problem, cause otherwise there would be more compression than that on a leaky cylinder. BTW, I haven't done a leak down and I have no CEL codes! Would a leak down show me anything? What should I do?

Yeah, 10 is pretty bad. First thing double check the compression just to make sure. Try pouring a half cap of oil into the cylinder and retesting it - any rise in test compression is from ring damage. Then I would pull the valve cover and look for damage on that cylinder's cam lobes as well as the valves and springs - see if anything is wrong from up top. Ultimately if it is a problem with the valves you're just gonna have to pull the head.


95 Eclipse RS : 5 speed
15.7 @ 87.9mph
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

leak down right now

Well, I did put a couple of teaspoons of oil in and it only raised the compression to 30.x( Guess that means I have head problems. I'll probally just leave it alone for now. Because the RPM range I usually drive in (~3500 RPMs) is where the car starts to drive normal again. Plus I have no money to do a head job. Also, the Eclipse is just my beater car. But I'm still wondering what would cause a bent valve problem like that when the timing is dead on. Maybe I have a burned up valve?

you're leavin a smoke trail ha?

i bet its the valve on that cyl

There is no smoke at idle. Only a little when I get on it hard.:shrug Is there some sort of oil additive that could help it, if its a, hopefully, burnt valve? Like Lucas oil additive? Or do yall think its just a bent valve?

prolly not really a bent valve as much as a bad valve seal, a really bad valve seal. If it's something you've never done before i wouldn't try to do it yourself unless your mechanically inclined. It would be easy to mess something up in the head.

my car will sound like, bumbabumbubavrooooooooooooooomrooooooooahhhhhhhhhhhhh, kishhhhhh
www.dsmregistry.com/detail.php?carid=643
VW= The joy of driving
DSM= The frustration of fixing

Put that cylinder to TDC on the compression stroke, and put compressed air into that cylinder. You should be able to tell where the air is leaking from..Def sounds like a vlavetrain issue though..Could be a bad valve seat seal, or even a stuck lifter, keeping the valve open just slightly. I'd pull the valvecover off first, and check out the valvetrain on that cylinder.

Well, I pulled the valve cover, and from what I can tell, everything looks normal. So I'm guessing I have a busted valve seal. I wonder why it would just be on the number three cylinder and it doesn't seem to effect my top end performance, just low end, and a BAD compression test?:shrug I don't have the money to do a valve job on the car. I'm saving all my money for when I'm off on my own after I get married in February. What would yall do?