Low Compression #3 cylinder

[91boz]

My 91 4afe #3 cylinder is not firing due to low compression 75 psi. All the other cylinders are at 175 psi. The compression goes up to 155 when I squirt some oil into the cylinder an it looks like that the rings are bad? There is no smoke out of the exhaust when the engine is running and the heads were just rebuilt in May. The#3 intake and exhaust valves were replaced when the head as I was told by the machine shop that there was "Tuliping" on the valves. Does squirting oil into the cylinder and the resulting increase in compression point to the rings even though there is no smoke in exhaust?

[91boz]

One more note is that I poured some Seafoam into the cylinder #3 and noticed that it started to leak thru the exhaust manifold where it meets the downpipe. This was with the #3 cylinder in the top highest position. Now in this position shouldnt both valves be closed? How can the Seafoam find its way out thru the manifold?

[w203]

I don't recommend seafoam for older engines, if left for a long time the seafoam is bad for seals and such. That info may also help disgnoise the problem instead of being left out in the first post..... who knows what other info your not listing.

Check your gaskets.

[tashirosgt]

#3 could have been in the top position on the exhaust stroke with the exhaust valve open.
People have told me that you can do diagnosis by putting compressed air into the sparkplug hole and listening for leaks, but I have never tried it. I think it this would only be useful if the valve cover was off.

[Flashmn]

You wouldnt hear leaking through the valve cover off, because the ports dont open into the head. Compression test it done by turning the engine and getting a reading from that, so a piston wouldnt be stuck in the exhaust valve open position.

[mvftw]

A good way to check is to put air in the spark plug hole. Then listen for the hissing. Listen at the tailpipe, that means your exhaust valve is leaking. At the carb or throttle body, then the intake is leaking. Or you may have a crack in the head...

[Flashmn]

Considering blow-by also hisses in the intake manifold

[Bitter]

it could be stuck rings. try seafoam in the oil for 20 minutes with the engine running, drivingi around some, then change the oil and recheck compression. do that a couple times, use 1/2 the bottle each time. that could help to loosen stuck rings. my gf's 93 escort had this problem and seafoam really helped it out! it restored compression in the low cylinder and its been running great since. its alot cheaper and easier than tearing the motor apart, so give it a shot first.

[91boz]

Yes I also had success with Seafoam in my 89 4AF. The #1 cylinder was acting up just like this one and using Seafoam in the crankcase and into the cylinder freed the stickly rings. The thing with that car was that it was sitting in that condition for 3 months and when I started it up the compression was back to normal.
This afternoon I turned the crank 360 degrees and yes the exhaust valves were open so I can relax knowing that the valves are sealing properly. The bad news is if the Seafoam does not work then I need to take apart the bottom end.

Originally Posted by w203

I don't recommend seafoam for older engines, if left for a long time the seafoam is bad for seals and such. That info may also help disgnoise the problem instead of being left out in the first post..... who knows what other info your not listing.

Check your gaskets.

I am not hiding any information which would be foolish since I am asking for advise! I tried the Seafoam thing after I had posted to the forum.