You need to retest that #4 cylinder. A reading of 0 is really rare. I have seen valves with up to a quarter of the face missing, like a quarter of the pie was cut out, that still gave some compression.

I would also remove the valve cover and check out what is going on with the rockers and valve stems by the #4 cylinder. If a valve is stuck open, and that is something I have never seen in 40+ years, then since this is an interference engine, there probably is a big hole in the piston. Get a pen light and shine it down into the spark plug hole and see if you can see the top of the piston.

But at least redo that compression test, I have never seen a cylinder read zero before, except on a new car where the factory forgot to install the piston. The schrader valve on the compression tester could have been stuck open as well so check it too.

 

I'm inclined to agree with Keith. I've never seen zero compression on any engine I've ever messed with. And I've messed with a LOT of engines in the past 40 plus years I've been tinkering.

 

Oh trust me I've never seen a zero before I check it 3 times and got zero each time the compression gague was working like it should I even tested the other 3 cylinders and got badicky the same numbers as before... Thata my next step
Is to pull the vavle cover off and see wats going on. If it is a hole in the piston I'm
Driving the car into the scarp yard but I'm hoping it'll be a rare stuck
Open valve

 

At this point in time making decisions about a timing chain is a moot point.
You have a pointer to a serious problem.
Zero compression!
And no idea why!
Depending on the reason you will have to make a choice of what to do.
I see three choices.
1. Nothing, junk it.
2. Rebuild it, a technical decision based on available parts and your abilities.
3. Get a new engine. From where, used or long block and install it.
and there is a 4th one.
4. Pay to have it fixed.

And #3 and #4 most doubt will get you a new timing chain.
and if number two and a budget is a consideration I've known the Saturn timing chain to go 100's of thousands of miles with out a problem. To me it is a non - issue.
I probably would get one. It might come as part of a rebuild kit. I honestly do not know
and if you are doing the work and the budget is tight I would not worry about it. And if the budget is not tight?
Yes. Buy one from your favorite parts outlet and don't worry about the brand.

 

Well it's a lot to think about cause as the car sits I have 200 dollars into it. So i think I'll pull the valve cover and just do a basic inspection see if a valve is broke or stuck open... And if all appears okay I'll borrow a little snake camera from my buddy and look in the cylinders see if there's a hole???

And if there is I guess my best bet is to just drive It to the junk yard.

It's Werid how it running on 3 cylinders and once u above 2000rpms it runs great still will get up to 80mph on the freeway and etc

 

Personally, I think there is a valve that is stuck wide open on cylinder #3. One step at a time. The first thing to do is get that valve cover off there and see what's going on there with the valves. If you don't find one or both stuck open from carbon build up or some type of failure, then get that camera down in the cylinder and see what's what. I don't understand why it will turn 2000 rpm and run 80 mph either. I had a buddy once that had a Datsun break a camshaft and run on 3 cylinders and it ran like crap. He asked me to help him figure it out and when we pulled the valve cover and he cranked it, I could see the camshaft was broken between #3 and #4 cylinders. I'd never seen it before that car and never seen it since. But anything is possible with moving parts and high rpms.

 

Yea In dumbfounded I wish I had a go pro to upload a video once I'm going down the road it runs great has power to pass people feels zippy but it barley idles and starts hard gonna press the gas pedal down sometimes... Well I'll post a update once I pull valve cover. I'm in the middle of replacing the transmission in my truck so when it's on the road next week I'm going to tear into the saturn


Thank you all so much for all the ideas and advice and opinion I feel this group is going to be a great place to get help and answer

 

Well, good luck. As it has been mentioned, the engine is an interference engine and while that basically says that if a valve is stuck open it stands a good chance of putting it through the top of a piston. As this is an overhead cam engine which pretty much says no push rods, I have yet to see a valve stuck open, closed maybe but not open. And closed it bends push rods, but with no push rods to bend the question still is why is there zero compression and what is it that is broken. A snake camera is a good next step.
The sad thing it seems to me in this day and age. The pressure is on to either purchase or lease something assuming what ever your financial situation is keep paying for a car on a monthly basis rather than owning the thing out right. And with repair costs as high as they are, discouraging repairing a lot of good basic transportation cars are just flat junked rather than repaired.
Oh Well

 

Had same issue with 97 sc2 w 185K on it. significant oil burner.
Drove 600 mi on 3 cyls. No smoke out tailpipe so don't think hole in piston
Saturn mechanic said no matter the cause I probably washed the cylinder on the trip home and a truly successful rebuild was unlikely. I pulled the injector wire for #4 to keep from dumping raw gas into my cat con.
Seeing no point in diagnose on an engine that could probably not be successfully rebuilt I opted for a fully rebuilt replacement through saturn. Costly.. came w a 3 /36k though

I suspect either some issue caused a valve to stick closed and later on in time (my trip) it burned, or the valve is bent or hung up as stated below.


Drove it for 10 months on 3 cyls till it failed NJ inspection due to ODBII camshaft and misfire codes. But you are odbI which detects nothing so you can likely pass state inspection if you pull the injector wire.
See no reason to dump the thing. It runs and can be either a spare car or a daily driver. For 200 bucks and some time and some more money you may be able to fix it if it is head related. If not just put it back together and keep driving it.


So I don't know what the ultimate cause was but I've tried to give you all the scenarios that went through my mind.

 

I have an explanation of you. Its all about timing. Lets say you have a badly burned valve, one that is burned even more than the ones I have seen in the past. Now that means that there is a gap there and that gap will pass X amount of air per unit of time. When the airflow or air pressure increase due to reduction in volume (compression) is lower than the unit of time to pass X amount of air, the pressure will remain at zero.

You are cranking the engine at a pretty low speed so the unit of time to pass X amount of air is pretty great. If you start the engine, at idle, the unit of time is less, but the pressure (compression) could still be pretty low resulting in a rough idle. As you increase engine speed, the unit of time decreases even more, so X amount of air has even less time to escape through the breach, causing the pressure (compression) to increase even further and could even get high enough to start igniting the F/A mix and getting some combustion.

While the power contribution of this cylinder may not match that of the others, it and the momentum of the crankshaft and flywheel will result in a smoother running engine at higher RPMs (say 2k and higher).

Good news though, I don't recall you mentioning that the engine produced a lot of smoke at speed. If you are getting any combustion in that cylinder and there were a hole in the piston, you would get a LOT of smoke. You would be sending burning gasses right into the oil pan. Your dipstick would blow out too.

I'm just saying, that if you have a burned valve, exhaust most likely, it would have to be burned very badly to get zero compression. I have seen them burned enough to get compression readings down to around 30 psi, but I have yet to see a zero, but it could happen.