sam even #1 looked low, which is odd.....i don't see how it let go so fast, how were the AFRs while driving around this week?

I would almost say its the hg because 3 and 4 are both off by about the same amount. You need to do a leakdown and see if air leaks out of 3 when you are testing 4.

All right, I figured somebody would recommend a leakdown test. Other than the blue smoke and the compression numbers, it seemed to drive OK. I pulled the intake to verify there was no blow-by through the valve-cover breather tube, pulled the coupler at the throttle-body... no oil so I assume the turbo is good.

On the last run of the night, I blew the dipstick out and coated the back half of the engine bay. I drove it home right after that, and this morning when I started to drive to work, I noticed the smoke out the exhaust, brought it straight home and drove the truck.

AFR's were in the 12 range everytime I looked down at the laptop under boost. I never got the chance to do some datalogging, but I think it was just a tired motor waiting for a little extra push to send it over the edge.

However, I think a little more investigation is in order. I will do a leakdown test. What's the most efficient way of doing it? And I will go for a decent drive this weekend to see if there's just some residual oil somewhere that's burning.

And thanks for the link Jay, but swinging $1k out of her is in the realm of possibility... $2k takes us that much further away from a new set of tits and I can't put that on the back burner for a motor.

sorry to hear that, and just got your ebc workin too :cry: I'd say find a clunker to swap in quick and save up to fix the one you have.

That is one hell of an upgrade. My ex-g/f got implants like 2 weeks after we broke up. They ended up looking like shit so no big deal. Went from an A to a D.

HAHA, nothing like motors and tits!

sam what was your proceedure for the test? cold? try wet? oil on plugs? throttle open?

I'm keeping my fingers crossed for you that it is just a HG or something, but if you do decide to go the used engine route, there is a place in northern NJ (I know it's a hike) that sells low milage <50k engines from Japan (JDM yo!) with most of the accessories attached for around $550-600. I told olderguy about them for his friend who was looking for an engine so he might be able to give more input. I found the place when looking for an engine myself and negotiated them down to $500 for pickup. Ebay the valve cover, CAS, coils, starter, alternator, throttle body/IM, injectors/rail, etc... and you'd be at a decent price point. If you want the info, PM me as I'll have to dig it up as it's been awhile.

Of the two JDM Yo engines I've seen, both of them had trouble. One of the "50k" motors need rings. The other had so much crap in the cooling system that it ruined a rad and a heater core. They both came from the same importer, so this might not be typical.

If the Miata isn't your daily why not tear down the motor you have and rebuild it. At least that way you'll know for sure you've got a good motor.

^Good points, that's the info I need to hear to make a good decision. I'm not decided by any means, so keep the options coming.

As for my compression test:
Cold motor.
Unplugged MS
Un-grounded fuel pump.
No throttle application.
Started at 1 and worked back, replacing the plugs as I went.
Each cylinder needed 6-7cranks to get to full pressure.

The plugs were dry, and looking at the plugs, I'd say #1 was running a tad leaner than the rest...but I'd only been MS'd for about 2hrs total run time.

Redo the compression test with the engine warmed up and throttle wide open during testing.

I only got $300 or $350 for the 1.6 motor that I sold, it took a month to move, and it was complete from oil pan to cam cover with all sensors except the thermoswitch (because I needed it on the other car). And it was a good longnose with compression 200 +/-5 on all holes. So I wouldn't spend $600 on some unkown "JDM" motor. Plus, if you got into a build, you'd have more effort involved but a pretty similar financial outlay, and at the end you'd get to replace the weakest link in the block: the rods.

+10x9

warm engine, pull all the plugs, unplug MS, start at #1, WOT, crank until it doesn't make anymore compression

redo with a 1/2 teaspoon of oil in each cylinder.

Hopefully it's not that bad- like a head gasket. You might even check the torque on the head bolts. I retorqued a head on KL v6 and manage to seal up the head gasket around the cylinder. Regained all the compression and ran that way for another two years.

If it's worse, pull the head, figure out what's wrong first. If it is the rings, and the bores are round, you can just re-ring with a cylinder hone.

Typically, I pull all the plugs to do the test. And 6-7 cranks to full pressure seems pretty normal. Also, the last time I did a compression test (this past Monday after I found the oil on the valve cover) I did an experiment where I tested one cylinder twice, with the throttle open, then closed. It actually didn't seem to make much of a difference. Maybe 10 PSI tops, and took slightly longer to get there.

As to a leakdown test- the cheapest tool I know of (apart from the one you borrow from a friend) is here: http://www.harborfreight.com/cpi/cta...emnumber=94190

Actualy on my nissan i saw numbers of 110 or so with throtle closed and numbers of 170-180 with the throttle closed. So yeah it makes a big dif there joe at least for me it has.

No shit? Wonder if it has something to do with the design of the idle valve or the PCV system or something... Like I said, it took a bit longer to build up compression, but it did finally get there (or nearly so). I'm pretty sure I don't have that big of an intake leak. :D

i get 110 across with the throttle closed and 190 open.....its the mere fact that the butterfly valve isn't open and theres not enough air pulled in to make high compression, i suspect if you crank it at least 20 pulses it would build.

Ok, moral of story: open throttle plate when cranking. :bigtu:

^It'll be the first thing I do when I get home..

Theoretically, what it the difficulty scale of replacing a head-gasket with the engine still in the car?