OEM compression spec

[jimbo74]

Hi, new to the site. Not new to vehicles. I am helping my dad work on my sister's 1999 Civic Ex Coupe, it is a manual tranny, and a 1.6L SOHC VTEC

Sister originally had issues with poor running conditions

My dad has concluded based on a shop's recommendation that his timing belt is bad and needs to be replaced.

compression that my dad tested it at was a dry test reading of somewhere around 100 psi per cylinder. is that correct? all the cylinders were within 10 pounds of each other

 

[RonJ]

Spec is about 180 PSI. Even though your cylinder compression numbers seem low, they are probably fine. If you wish to redo the compression test, it should be done with the engine fully warmed up, all spark plugs and the ECU fuse removed, and the throttle wide open.

Is the ECU throwing any CEL codes? Can you provide a more detailed description of "poor running conditions"?

 

[jimbo74]

I am going to need to talk to my dad again.... from his original report, he said a shop said this:


SYMPTOMS

--------------------

Poor acceleration

Engine misfires at idle (as heard thru tailpipes)

Engines shakes car when accelerating in any gear, smooths out as you back off the gas pedal.




OTHER SYMPTOMS

-----------------------------

No blue or white smoke

No high pitch whining

No overheating or loss of coolant

No loss of oil

No oil mixing with coolant (radiator cap clean, no oily film)

No coolant mixing with oil (dipstick clean, oil only)





SHOP DIAGNOSIS

---------------------------

P04020, CAT Efficiency, Lo Bank 1

P0301, P0302, P0303, P0304 All Cyinder misfire

P0300 Random Multiple Misfire detected

CYL#1 120 PSI, #2 50 PSI, #3 55 PSI, #4 105 PSI, (CYL #2 & #3 LOW, REPLACE ENGINE)

 

[RonJ]

Ignoring for now the discrepancy between the shop's and your dad's cylinder compression numbers, I would think that the first thing to do is a full ignition system tune up - replace plugs, plug wires, distributor cap, and rotor and then adjust the ignition timing. If afterwards, the engine runs well, then reset ECU to clear codes, drive car, and see whether P0420 returns. If so, replace the cat.

If the engine still runs poorly after the tune up, then test the coil and ICM inside the distributor.

But before all this^ is done, have your dad repeat the compression tests under the conditions I mentioned in my previous post.