Engine compression test

[emcwill792]

I did an engine compression test today on my 02 Galant since I am still having problems with how the engine is running.

Readings (From Left to Right facing the car)

1. 120 Psi initial / 175 psi wet
2. 125 Psi initial / 175 psi wet
3. 122 Psi initial / 155 psi wet
4. 125 Psi initial / 180 psi wet

Does this give any clue as to why my engine is running like crap?

[qnz]

Is the engine warm when you did the test?

[emcwill792]

Wasn't up to normal temp, but wasn't freezing (I'm in Florida). Should it have been?

[qnz]

When people quote compression numbers, its always on a warmed up car. I dont have the manual handy right now but it should be 170 psi +/-5psi IIRC.

Tho the fact that your compression numbers are all the same across the board is very good. Except when you added oil into cylinder3. I forgot what that means? Leaking piston ring? Maybe someone else can chime in about that.

[Stewi]

The wet#'s dont make sense because the dry#'s are all consistant. Usually a cylinder with a bad ring will read low dry and jump like 50psi when wet, I think the problem here is the motor wasnt warmed up.

When you do a compression test drive the car around first and get the car fully warmed up, listen for the fans to turn on, thats when its at operating temp, then pull all the plugs (wear gloves they are gonna be very hott) and do the compression test. Also when you do the test, you pull the MFI relay so you dont get any fuel or spark, all plugs should be removed from all cylinders, not just the one being tested, and the throttle needs to be wide open, so you need to have the pedal on the floor while your cranking.

[emcwill792]

Ok, redid the compression test this morning with the engine up to operating temperature. Those plugs were definitely hot! =)

Readings (From Left to Right facing the car)

1. 120 Psi initial / 210 psi wet
2. 121 Psi initial / 183 psi wet
3. 122 Psi initial / 181 psi wet
4. 120 Psi initial / 211 psi wet

So, does this give us more of a clue?

Symptoms are: runs rough when warm or brought to idle from higher RPM, has a ticking/pinging/knocking sound, just does not seem to run as a galant engine should. Some mosture droplets from the tailpipe (although could this be due to florida humidity?)

[qnz]

Your compression numbers are still very low for a warm engine. Are you doing it right? regardless, you still have consistant numbers across the board which is good. Means your headgasket, piston rings, and valves are sealing good. Rough running could be something as simple as changing the oil to a high performance oil. What is your idle at? moisture droplets are also normal when starting the car for the first time during the morning.

[emcwill792]

I'm sure I did it right. Made sure the engine was warmed up (drove it 20 to 30 minutes), pulled coils/wires/plugs, pulled relay. Then made sure the compression test hose was tightly screwed in to each plug hole. Had my girlfriend prses the gas pedal to the floor and crank it through 4-5 revolutions.

I've changed the oil, using the Max Life product. Idle is sitting at about 700-800 RPM.

I don't know the maintenance history of the car, as I recently acquired it.

Originally, the car had these check engine codes:
1. P0421 - Warm Up Catalyst Efficiency Below Threshold (Bank 1)
2. P0300 - Random/Multiple Cylinder Misfire Detected
3. P0128 - Coolant Thermostat Malfunction

The work I've done so far is:

1. Fixed timing belt problems - Oil pump and balance shaft were out o time. The rest of the timing marks were lined up except for those two. This has made the engine run smoother at higher RPM, but not helped much with idle.
2. Replaced spark plugs.
3. Replaced valve cover gasket and spark plug tube seals
4. Oil change
5. Replaced O2 sensor.

I've had a Galant in the past (an 01), and I know they can be somewhat louder than some other cars, but never had mine run this rough. I'm just trying to get this one up to running condition to replace my Infiniti I35 (last Nissan product I'll ever touch).

[emcwill792]

So, what you're saying is that my engine running rough is coming from somewhere else? Anything else that I should be checking?

[Stewi]

So, what you're saying is that my engine running rough is coming from somewhere else? Anything else that I should be checking?

Try this.....


get some brake cleaner or carb cleaner or starting fluid (any will work) and start the car let it idle and spray it under the throttle body where it mounts to the intake manifold. It sounds like you might have a cracked intake manifold causing the engine to run rough.

[emcwill792]

What result am I looking for? Just did it, and no change in how the engine ran. Wish I had some friends down here in SW Florida to take a look at it =)

[Stewi]

What result am I looking for? Just did it, and no change in how the engine ran. Wish I had some friends down here in SW Florida to take a look at it =)

Usually if its cracked the RPM will rise quickly or make it sorta sputter because the brake cleaner/starting fluid is combustible.

[emcwill792]

Didn't have any change in how it ran testing that. Any other suggestions?

[emcwill792]

Well I broke down and took it to a local repair shop to have them do some diagnostics on it. Initial inspection shows that a good portion of the roughness/loudness is from the rear engine mount and the transmission mount. They said after they replace those they'll be able to see if there were any additional issues.

$450 to replace both mounts.

[Joshua42007]

Well I broke down and took it to a local repair shop to have them do some diagnostics on it. Initial inspection shows that a good portion of the roughness/loudness is from the rear engine mount and the transmission mount. They said after they replace those they'll be able to see if there were any additional issues.

$450 to replace both mounts.

sorry to hear that. was that the price for parts + labor?

[emcwill792]

Yeah, parts + 2 hours labor. I'm hoping this is the only issue - sinking far too much cash into cars at the moment between this car and my I35 - just trying to get one of them running well.

[emcwill792]

Got the car back and that's what it was - mounts. Runs much better. Just have to change my oil pan gasket and I'm good =) Saw the mounts, one was torn really bad, one was obliterated.

[qnz]

I guess $450 sounds about right for new mounts + 2 hours labor. You could also very well swapped out the mounts yourself and saved $200 in labor cost. Glad you solved the engine roughness

[emcwill792]

True, just don't have the tools yet to do it (not changing mounts with a scissor jack =), and haven't done it yet so not sure how bad the experience is. Plan to do the oil pan gasket myself, and get more hands on with this car

Really want to restore it to a better state appearance wise too in the future, but not sure it's worth the $$ yet to fix the dents and have it repainted.

[qnz]

oil pan gasket is easy.

You could have changed the motor mounts one at a time and not needed to use a jack to hold up the engine. 3 mounts is sufficient to hold up the engine and tranny for a medium period of time. Now you know, when its time to change the other 2 mounts.

[emcwill792]

Did not know that - learn something new every day =) I figured the oil pan gasket should be easy - just get the gasket and RTV sealant and do it when doing my oil change, correct?

It's good to be back driving a Mitsubishi.

Also, any recommended online vendors you guys use for Mitsubishi parts?