uneven compression

[eclipse4life]

My car feels like its missing at idle. Ive had the head rebuilt because the valve stem seals was bad the head got new valves and seals with stock hg about a year ago. I initially thought it was ignition related so i changed the coil pack and power transistor along with msd wires and stock plugs that did not fix the problem. I did a compression on the car and 1,2,4 reads at 150 +/-2 and cly3 reads 132 +/-2. I did a wet test on #3 and first reading was 90psi then it climbed up to 146 after a couple of strokes. It doesnt smoke oil from what i can see. could this uneven compression be what my missing is coming from and is it possible that the car might not smoke even being that low what are your guys opinions. im leaning towards rings but i would like to see what you guys think.

 

[nightspeed87]

those numbers do seem kind of low, id think your rings were worn and your performance wouldnt be 100% but i wouldnt see that causing the problems of what your saying. Check out your airflow sensor and see if its malfuntioning because mines idles rough when i have my coolant fans blowing directly on it with an exposed KnN filter.

 

[eclipse4life]

first off thanks for the response but if it was the mas sensor wouldnt it affect not only idle but all through your rpm range as well im not sure just asking a ? also the engine shakes back and forth not voilently but as you would feel an engine missing to that effect. the car pulls hard i have the boost still at stock 7psi but ive had the car for about almost 2 years and it just does not feel strong as it did then. so thats why i was thinking that piston 2 and 3 not being closer in compression was throwing off the balance causing the engine to shake back and forth and im sure missing in that clyinder. Not sure just looking for someone that knows if that could be the problem

 

[Splitpi]

It sounds like your rings, especially after the wet test jumped the PSI up... sorry man

I'm battling a low compression cylinder aswell.. well not really low so much as out of spec (differs by more than 14 psi from other cylinders). But I am 95% positive its a valve problem for me...

 

[eclipse4life]

thats fine i thought it was rings to just wanted someone else's opinion. Know ill decide whether or not to leave it a 2litre or stroke the motor. why do you think its your valves

 

[DSMark]

It sounds like your rings, especially after the wet test jumped the PSI up... sorry man

I'm battling a low compression cylinder aswell.. well not really low so much as out of spec (differs by more than 14 psi from other cylinders). But I am 95% positive its a valve problem for me...

correct me if i'm wrong but i thought the psi is supposed to jump up on a wet test and its bad rings if it didnt jump up.

 

[Splitpi]

correct me if i'm wrong but i thought the psi is supposed to jump up on a wet test and its bad rings if it didnt jump up.

You have that reversed. The only thing you can tell will a compression test is:
1) The pressure in cyclinder
2) If you pour a cap full of oil into the cyclinder on an out of spec or low compression cylinder and compression rises, then its the rings, otherwise its a valve issue or possibly headgasket (not likely).

You have to do a leak down test to figure if the leak in pressure is due to exhaust, intake valves or head gasket after doing step 2. Oil poured into the cylinder doesn't flow uphil into the valves to seal them better when doing wet compression test.