Stuck valve?

[lotusflight]

Got new plugs gappend and installed. Now the fun begins. Still the cold starting us rough and a lot of "coughing". It wont hold at idle, sonhave to keep on revs until engine warms up a bit. Then it idles at about 900-1000.

Performed a compression test on each cylinder. Counting from passenger (US) side, #1,2,3 all showed between 140 and 150. #4 though was a bit concerning. At first there was no reading at all after a few good cranks. I thought the cylinder rings or head gasket was shot for sure. Then as I kept cranking and the engine started running on the other 3 cylinders, pressure in 4 read a bit sporadic- jumping to 100, going down again, jumping to 120, going down, then it settled at 150, and after shutting off the engine it held the pressure. Makes me think rings and gasket are ok, but perhaps something is going on with the valves. Any ideas you guys can suggest?

[FunElan]

When it's warm does it smooth out and drive normally?

If so...I bet it just wants to be driven. How's oil pressure? The valve system is hydraulic vs solid.

[lotusflight]

When it's warm does it smooth out and drive normally?

If so...I bet it just wants to be driven. How's oil pressure? The valve system is hydraulic vs solid.

Thank you. It does smooth out - sort of. Since I really don't have any experience with this Elan, I am still learning what normal is and trying to get a baseline. Also, after the new spark plugs, I am yet to clean the injectors, replace the oil filter and adjust the timing. That #4 erratic compression is what really spooked me.

I actually captured the oil pressure and revs as I tested it atb 950 idle rpm and at about 4k.

[lotusflight]

Does the oil pressure look low? I saw on this one start video at idle, the oil pressure is above 5. Mine is waaaay below.

https://youtu.be/Mvlr5eJZmeI

[TorqueHorse]

Oil pressures look fine to me.
Agree that if it hasn't been driven in a while that exercising it first (if possible) will help you get a better base line of what seems out of whack.
A leak down test might also help pinpoint the area of where the low compression is coming from.

[Tuga2112]

heres a random tought.

get it warm. and if til stop making the noise.
then use engine flush and run it for a few minutes to let it have some effect around the engine. you want to clear out as much crap as pracitcally possible when you do the oil change.

put 10-40 in. and see how it goes.

10-40 is a grade that even if its not "right" it will be "right enough" to not cause any harm

new "wrong" oil will be better than old oil

[FunElan]

Does the oil pressure look low? I saw on this one start video at idle, the oil pressure is above 5. Mine is waaaay below.

https://youtu.be/Mvlr5eJZmeI

Your oil pressure looks good for a warm engine. When mine is dead cold it definitely reads almost 9 and comes down as it warms up. This is why I changed my oil cooler lines (the original ones blow)