Low compression on rebuild

[ozzyleven]

So, after totally bombing the emissions test, I'm troubleshooting the new 22re again. The emissions test was totally bunk, the mech at the shop called me and I guess their sniffer was on the fritz, bad sensor inside or something. I'm bringing it back in next week to try it again.

Anyways, due to paranoia, I did a compression test today and got 115 psi on all 4 cylinders. I don't know if I screwed up the test or my engine sucks, but I followed the FSM and repeated the test twice. 115 is a far cry from the 180 psi the engine supposedly had when it left. The one thing it does have going for it is consistency...

The engine has about 600 miles on it and it does not appear to be consuming oil. Gas mileage did drop though after the valve adjustment (which I confirmed was to the builder's spec). I'm getting 16 mpg :ybrick: The knocking 180k 22re I replaced got 22mpg. At this point, I don't know if I should continue troubleshooting things or what to even look at next? Should I give it more time to break in?

 

[CodeButcher]

If you had blow by that would arribute to the high HC readings. Basically your burning oil. That and old CAT too.

That knocking could have been caused by a plugged CAT. I had the same problem in my 86 PU. It would diesel when put under a load, like climbing a hill. Too much back pressure for the exhast gases to escape properly.

 

[KidVermicious]

Did you rebuild this yourself, or have it done?

 

[SV_Dude]

You only have 600 miles on it. The rings haven't had a chance to seat yet. Give it another 1000 miles and test it again. Your mileage will not be as good at first but it should get better. Did you have your fuel injectors cleaned and flow matched when you rebuilt your engine? If not, I would suggest getting that done.

Also, when you are breaking in your engine, how are you doing it? It is a little late for this step but when you first drive with your new engine you want to drive it like you stole it. Beat the ever living crud out of it for about 100 miles or so. That will allow the rings to seat good under a high engine load.

 

[ozzyleven]

I had this engine built by a builder that has a pretty good reputation for 22re engines. For the break in, I was told to drive it harder than normal, but not too hard (builder's opinion). Basically, I push the truck as much as possible, vary the rpms alot. Not quite 'drive it like you stole it,' but it definitely hasn't been babied too much. There was so much conflicting opinion on the net about breaking in engines, that I just listened to the builder...

Injectors were flow-matched and reworked. When I got the engine, they supposedly tested it at 400 rpm on some simtest thing. My paperwork says that it had 180 psi on all cylinders then. I don't really know why it would go down.

On another note, when I had the spark plugs out and was shinning my flashlight around, I noticed the tops of the pistons are already getting a light coat of carbon buildup. Does it really happen that fast? Or is something causing it?

 

[mikebontoft]

everything sounds completely normal.

 

[mikebontoft]

Now who said your engine had 180 psi? the guy that rebuilt it or did you get it from a jdm place or junkyard?
I think they just run a relative compression test and come up with a number if its the used engine.

can you explain in detail how you did your compression test? please don't say its in the fsm. I want to know how YOU did it.

 

[ozzyleven]

It was done by a builder. They put their engines on a simtest thing before they leave the shop. The print out for mine said like 35psi oil at 400 rpm and 180 psi compression on all four cylinders.

To do the compression test, I took all the spark plugs out. Undid the cold start injector, undid the ignition stuff. Screw the tester into cylinder. Hold throttle wide open while friend cranked the engine for about 5 seconds or so. Got engine hot before the test. Tried to work as fast as possible to maintain warmness.

 

[mikebontoft]

Ok, you did the compression test correctly. thank you.

As for their test... any chance you can find out how they do it? Im still holding them to a relative compression test. might be worth talking to them about your experienced compression as well.