Compression test??

[gotboost55]

what should the normal compression be on a 92 plymouth laser turbo??/if its really low what does it mean, i dont know how low it is but i will find out when i call my mechanic tommorow,does this mean i have to rebuild my engine?thanks!!

 

[kyanox]

How low is it?? Have you run comp tests on all 4 cylinders, or are you talking about a vacume test?? Just currious.

I was told between 120-150 is good, anything lower and you'll have issues and will probably need to have your head's serviced, and rings checked.

 

[purplehazetsi]

Low compression doesnt really mean that you need a rebuild. Low compression COULD mean your rings have wear on them. When you check all 4 cylinders the compression should be within 15psi. If you have consistant numbers than you should be ok. But if 3 cylinders have lets say 150, and the 4th has alot less, than do a leak down test. It could mean your rings are toasted,Intake/exhaust valve leak, or even the head gasket is bad. I would srongly recomend you go to Napa or something and pick up a compression tester, they are like 20-40 bucks. I dont trust anyone to tell me i need a motor rebuild but me. I went to a mechanic and he told me my motor was shot and the compresion was 70 across the board. so to make sure i did it my self and i had 155 across the board. The jerk wanted the $$$$ to do the rebuild....... good luck post your results when you get them

 

[gotboost55]

I just got my ride back today ,and the mechanic said the compression turned out to be 115,120,140 ,140,he said the first 2 are low,and i think this is what is causing the rough idle and the misfires,so whats the next step to fixing this problem,leak down test???could a shitty headgasket cause this???should i even bother with the car??

 

[gotboost55]

somebody help!!!

 

[Talondsm18g]

Have a leak down test performed. It could very well be the head gasket.

 

[purplehazetsi]

yeah it could be a head gasket or leaky valve seals, do the leak down test.. if it comes out the exhaust then you have issues with the exhaust valves, if it comes out the intake, then its the same problem as the exhaust side but just intake seals, and if it comes out the dipstick, well then you should keep in mind you will need a rebuild because its your rings. Oh and also not that the number 2 cylinder will always lose compression first. well good luck keep us posted

 

[tsunari]

Take a look here- this should help out:

http://www.dsm.org/menu.epl?item=485

 

[gotboost55]

Thanks for the help,in about a week am doing the leak down test i'll u know as soon as i can!peace

 

[tsunari]

another suggestion you can do is if you cant get ahold of that gague, just turn whichever cylinder you're testing to TDC (on the compression stroke) and then pressurize the cylinder. If the intake valves aren't seating, you'll hear air rushing through your intake manifold. If it's the exhaust valves, you'll feel the air coming through your tail pipe, and if it's your head gasket, you'll probably see your cooling reservoir level rise up.

-Good luck

 

[gotboost55]

Could this be why am having idle surge because of low compression??thanks

 

[tsunari]

not sure- I have burned/sticky #3 valves and I'm only idling rough (hoping to get it fixed soon). As for idle surge . . . the only time I've seen it was when the EGR valve was sticking. I was advised to buy a new one, but not being made of cash- I tore out the old one, cleaned it and put it back in. It's difficult to clean though (lots of carbon build-up).

 

[1995 brian]

I just did a compression test on a 97 gsx and it came out 120 all around and that was a dry test didnt have time for the wet test. (Got dark on me) but im pretty worried because i read that 164psi is a good number anything under that is low.
Any predictions on what could be going on?