I felt the engine run much smoother during driving. When I stopped at the red light, I can feel at the first 10-30 seconds, no misfire at all but then the engine started shaking. Unsure why the misfire happened not immediately when stopped the car but after several seconds.

 

Sorry for being quite a while for my updating. I have finally done the leakdown testing. A lot of tricky things: 1) taking out the driver side tire made me much easier to access the crankshaft pulley. I also took out the shield in order to reach the pulley bolt. 2) It took me quite a while to figure out how to put the gear to neutral and get the key out. There was a small square "window" under the drive wheel. You can pull the cover out and feel a reset button in it. I turned on my engine, put the gear to neutral, pushed that reset button and then was able to pull out my key. 3) I recognized the cylinder #1, #4 went to TDC together at the same time #2, #3 went down all the way. So it was different from my previous car which all of the 4 went to TDC together. I rotate the crankshaft till the #2 and #3 went to TDC before I started my leakdown testing.

Coming back to the result of the leakdown testing: I heard the air leakage noise when I was testing cylinder #3 while didn't or hear any percentage lost on the other 3 cylinders. I couldn't figure out where the air leakage noise was from after trying several times. Finally, I found the cold air out from the tail pipeline, not very strong, I couldn't hear the noise there but I could feel the air flow out from the pipe. I assume this mean the exhaust valve issue.

Any idea of an inexpensive repair? I mean without rebuilding or replacing the engine?

 

Each cylinder is at true TDC at a different time. It sounds like you tested #2 and #3 from the same position?, which would give false readings. At TDC for #2(between compression and power), the exhaust valves might be open on #3(between exhaust and intake).

Not the easiest test to perform. If you're not perfect at TDC, the 100 PSI wants to push the piston down!

The firing order is 1-3-4-2

 

Yeah, I tested #2 and #3 from the same position. I also tested #1 and #4 from the same position. #1 and #4 had the same readings. Unsure if that matters though. Seems I shall run another leandown testing.
thanks a lot.

 

Sounding a lot like a burned exhaust valve in #3.

 

Or it’s open because it’s not at TDC.

 

X2
Based on net_managers "understanding" of which cylinders are TDC, I believe he did the test incorrectly.

 

However, didn't really need the leakdown after the compression showed #3 much lower.

 

Yeah, it was much lower on #3. Adding engine oil brought the compression from 120 to 150-170 psi while other 3 cylinders showed 210 psi. The leakdown testing I did was more about figuring out where the leakage was instead of which cylinder had the leakage. The percentage gauge is not that much useful to my case since I am pretty sure the #3 has an issue.

 

I redid the leakdown testing. I tried 4 times, each only based on my observation of #3 being on TDC (I was looking at the stick into the #2 hole before). Among the 4 times, when I tested #2, I observed air out from tailpipe three times and no leakage once (guess this was a false result?), while everytime #3 having the leakage from the tailpipe.

Sounds like an exhaust valve issue?