Compression...yeah, about that....

[jthod]

Just got in after checking mine. Stock 3.0, 124k, regular oil changes, 60k top and bottom done at 104k (me), as well as rod bearings.

Just after getting the exhaust done, I noticed smoking at WOT. I was told black smoke, so I thought rich. Thermostat, ECT, temp switch, and black smoke was gone. Now there was blue smoke.

I parked it about a week ago, and just got to testing it tonight. I was thinking probably valve stem seals. I had a miss at start-up after sitting for a few days, and oil was caked on the back of the valves.

Test was done after it has sat for about a week, so it WAS NOT at operating temps. I can see the sompression being slightly lower, but not like this.

Compression was as follows:

Cylinder #1
dry-110psi
wet-110psi

Cylinder #2
dry-90psi
wet-140psi

Cylinder #3
dry-60psi
wet-95

Cylinder #4
dry-90psi
wet-90psi

Cylinder #5
dry-50psi
wet-70psi

Cylinder #6
dry-60psi
wet-80psi

I guess it's time for an upgrade...

 

[hawkeye18]

Well numbers are going to be low if it isn't warmed up, but 2 and 3 definitely look pretty bad. The difference in numbers is the biggest indicator... sounds like a good time to go for some Wiseco pistons! :laugh_ti:

 

[jthod]

if only I could spare that kind of coin. I really don't want to spend money on this thing.

Kind of a shame, it's only got 124k!!! I baby the damn thing, and I get this shit?!?!

 

[hawkeye18]

Try letting the engine get up to operating temp (have it running a good 20-30 minutes to let the oil heat up all the way) then try it again. That really will give you a better indication of the health of your piston rings and/or valve seals.

 

[jthod]

I know, I already had the intake off to check the back of the valves, and it looks like I need to do seals also.

I gues I found my summer project, too bad it's not cheap or free.

 

[hawkeye18]

Valve seals and even piston rings are pretty cheap.

But then again, so is a blend door actuator...

 

[LJRuddy]

Joe, I feel ya broski. I think my next big purchase will be either a gun or a bicycle

Lets meet up, get drunk, and cry together. Maybe we can elope back to North Platte again!

 

[yamahaSHO]

Drive the car around, park it, pull the intake off immediately, one plug at a time (replace when moving to next) and check the compression. Be sure to crank until it stops progressing. If you get low numbers like that again, try another gauge.

 

[itwonder]

Did you have throttle plate fully open when you ran the compression test?

 

[yamahaSHO]

You really should have the intake OFF when you do this.

 

[CademiaX]

if only I could spare that kind of coin. I really don't want to spend money on this thing.

Kind of a shame, it's only got 124k!!! I baby the damn thing, and I get this shit?!?!

you should sell it to someone we can take care of it properly and you should ride the bus

 

[1993MTXSHO]

Does your engine run smooth or even semi smooth? If it does then those numbers are wrong, and the gauge is screwed up. With numbers like that the engine would **** around and run terrible and probably not have much power at all. Get a different gauge, warm the engien up, and run the test again.

 

[SHOZ123]

Get two bottles of Auto-RX. After 10k miles driving it hard it will run like new.

 

[1995SHO9]

Why are people saying to pull the intake to do a compression test?

I was told to drive it around for awhile, pull all the sparkplugs, unplug the dis, and then crank it over for 4 seconds and see where it hits.


Oh an don't worry about the rings dude, my 91 has blowby like crazy and still has the quickness. I burn about a quart every gas fill up. Drive the thing until it blows.


Oh, and I assume if those numbers were correct, it would run like total shit...

~Johnathon~

 

[yamahaSHO]

Why are people saying to pull the intake to do a compression test?

Two reasons. First off, it provides far less restriction to the cylinders to induce a more accurate reading during a compression test. Second, you don't have to work your way around a huge intake.

 

[1995SHO9]

Two reasons. First off, it provides far less restriction to the cylinders to induce a more accurate reading during a compression test. Second, you don't have to work your way around a huge intake.

"You can't change sparkplugs on a SHO without pulling the intake off".

 

[yamahaSHO]

Um... Okay...

 

[AREA 91]

Two reasons. First off, it provides far less restriction to the cylinders to induce a more accurate reading during a compression test. Second, you don't have to work your way around a huge intake.

This is true, but almost no one does it.

"You can't change sparkplugs on a SHO without pulling the intake off".

I wouldn't tale too much smack there little John. It takes you 2 hours to change pads and rotors.:laugh_ti:

Um... Okay...

Punch him in the face.






Joking.

 

[hawkeye18]

Next person who makes a spark plug joke gets his sunscreen put up on a tent pole.

Oh wait... :theyareontome:

 

[jthod]

you should sell it to someone we can take care of it properly and you should ride the bus

Thing is, I've taken great care of it. Bastard car.

Does your engine run smooth or even semi smooth? If it does then those numbers are wrong, and the gauge is screwed up. With numbers like that the engine would **** around and run terrible and probably not have much power at all. Get a different gauge, warm the engien up, and run the test again.

No, it runs great, other than the smoke. I used the guage at work the other day on a cold 7.4L engine and read 160psi.

I need to put it together and warm it up.

Get two bottles of Auto-RX. After 10k miles driving it hard it will run like new.

10k miles? Thats like 6 months of waiting. I've been thinking of running some of that through, that should take care of all the carbon. The top of the pistons are pretty caked.

Two reasons. First off, it provides far less restriction to the cylinders to induce a more accurate reading during a compression test. Second, you don't have to work your way around a huge intake.

X2, give the engine all the air it can take.

I'm going to through it back together and run it for a while and check again. I already found a 3.2 for $200, or a parts ATX for $400.