Do I need a bottom end rebuild?

[flumph]

So, I'm the guy that just finished rewiring and megasquirting my Eta (I was bored).

Before I rewired everything, I always had a high idle and a ticking sound coming from my exhaust. It also shook pretty bad under load above around 2,500 rpm (right when stuff starts to get fun!). This was part of the reason I decided to run a standalone. In the act of prodding around the "factory" harness, I discovered that one of the injector plugs had one of the leads hard shorted to the engine block ground post terminal. I thought, "cool, that might be why it's running weird."

So I get it to idle really nice and steady around 800 rpm, but there's still this bad ticking sound coming from the exhaust, and now it's dripping gas out the tailpipe! It's 100% not water, it's gas. Shit. It's a dead misfire.

So I get out the test light and sure enough, I'm getting a nice fat white inch-long spark on all 6 plugs, tested at the boot. So, it's not the wires, cap, rotor, or coil. It's not the injectors because I'm running some Lucas injectors from a junkyard M62 (191cc) that I cleaned and tested. Shit. Only leaves compression.

So I get out the compression tester and test it cold. Throttle open, all the plugs out, by the book. Here's what I found:

1. 150 psi (tested it twice)
2. 160 psi
3. 170 psi
4. 190 psi
5. 180 psi
6. 195 psi

Plug 3 had oil on it and plug 4 had some crusty white stuff that looked like mold on the prong electrode. All of them were pretty black. Sewed everything back up, torqued them all down, spun around the block, and it's still ticking and shakes under hard throttle above 2,500 rpm. It also does burn oil.

So the real question:
What's my next step in diagnosis here? The head gasket is 4000 miles old and it's never gotten hot. Timing belt is new, installed by someone who knew what they were doing (not me). When the head was off, it got tanked (but not sure if the valves got lapped or not). Cylinder 1 did wiggle a little, but it didn't seem like a concern. Head's not cracked. No coolant in the oil, no exhaust smoke. Just gas coming out the tailpipe.

What do I do???

Edit: I also listened to the change when I pulled each plug wire, and this agrees with the compression test. Disconnecting 1 and 2 didn't do much, but 4, 5, and 6 were drastic.

[e30davie]

Leak down test i'd say is the next step to determine where that pressure is leaking from in cylinder 1.

150 psi is lower than the rest, but is still plenty of pressure to at least get it to fire i would think.

I assume you have checked your valve clearances? With extremely tight clearances or zero clearance (?) it might be possible to hold the valves open long enough to release some compression and cause a misfire.

[digger]

Do a hot (warm) test and add oil into the low reading pot

what's wrong with standard injectors ?

[flumph]

Bad news.

Did what you guys said, and I warmed it up and then tested again both hot and hot with a straw of oil spooged into the cylinder.

Hot/hot with oil

1. 175 psi/215 psi (!)
2. 175 psi/240 psi (!!!!!!)
3. didn't test/200 psi

That's certainly not normal. If it was bad valve seats or worn valve guides making me lose compression like this, the oil wouldn't have made those numbers jump by 37%. I have bad rings. I need either a rebuild or a new engine.

To support this, I've only been really able to run the car at night lately, so my light was never great. I just did this in the sun and noticed blowby gases coming out of the return tube at the block (PCV is partially restricted because I'm waiting on a hose in the mail). Pulled the dipstick and there was a solid stream of blowby gas... She's done, boys. Leakdown test would be nice, but that's pretty conclusive. I also never would have been able to test it by pulling the dipstick unless I was running standalone speed density, because it would have just stalled the engine (unless I blocked the PCV hose I guess).

I have two theories.

• The PO was a bit of a ricer type. High school kid. I think he might have run it without an air filter for quite a time.
• That hard grounded injector would have been spraying fuel all the time. This could have feasibly washed the cylinder walls with fuel and stripped off the oil film that would normally be there. This wore the rings excessively, and now my engine is sad.

Not that it matters what happened. Either way, I get to learn how to build an engine! Mixed emotions. A little sad, a little angry, but honestly kind of excited. Luckily, a nearby junkyard has an eta sitting in it. Time to gather my tools and call up a buddy.

Anyone ever get a short block up a flight of stairs before?

[redlightpete]

Those wet compression numbers are probably just higher due to the volume of oil in there. As stated above, your compression numbers aren’t bad enough to explain your drivability issues. My old land cruiser ran fine with 90psi on one cylinder. You could do a leak down test if you’re worried about blow by, but there’s probably something else going on.

[flumph]

Best guess, I put about 7cc of oil into the cylinder (measured from my straw). An eta has a TDC volume of 57.5cc, from another thread. Good enough for estimating.

Assuming an equal quantity of gas, we can use Boyle's law. If I was getting 175 psi (lol mixing SI and imperial units)...
P1 x V1 = P2 x V2
1206 kPa x 57.5 cc = 1655 kPa x (unknown) cc

Solving...
Unknown would have to be 42 cc to make up for that pressure difference. I would have needed to add 57.5 - 42 = 15.5cc of oil to make that happen. More than double. And that's assuming that I got all of the oil in with my fat, knobby hands.

And cylinder 3, which shows fine cold compression, didn't skyrocket the same way with a similar amount of oil. And the piston in cylinder 1 was wiggly when I had the head off. And I have a foolish amount of blowby pouring out the dipstick tube.

I don't know why I'm not getting combustion with compression numbers that should be fine, but I'm not, and a lot of signs point to ring wear or cylinder wall wear. I'd love to be wrong. Maybe I am wrong, I don't know.

Edit: holy shit I just did a word problem in real life.

[e30davie]

Did you check the valve clearances. You are being awfully dramatic!

I had an m20 with a cylinder at 110psi hot and it still fired.

[digger]

despite the numbers suggesting sub optimal/ variable ring seal i think you also have a fuel issue as a root cause, to get raw fuel out the exhaust. changing to standalone its not hard to screw the fueling by accident. id make sure you get that part sorted before rebuilding anything

[flumph]

Ok, I just checked them. They were all a little bit tight, but they were consistently all tight. None of them were strangely loose. I backed them out a little, and I can start to hear a second cylinder misfiring (the two are close in the firing order that I can hear, so I'm going to guess it's cylinders 1 and 2 because 153624). Something is definitely weird. There's no reason it shouldn't be firing, but it isn't. Have fuel, have spark, have (sketchy but good enough) compression.

Either way, a B27 short block is $150 at PNP and I have a socket set, a moving blanket, a Jetta, and a free Sunday.

Could it be that something is cracked, and it's showing good numbers with the tester, but once the engine is in operation, that compression isn't present? Like a cracked ring land only opening up when it gets hot or something. I dunno.

[flumph]

As for the fueling, I have my AFR set for 13.8 at idle. Wideband agrees. In fact, the exhaust smells a lot less gasoliney with MS3 than it did with Motronic. The gas out the tail pipe is kind of intermittent too. I could be wrong there and it is really just water.

The shaking under load at higher RPM thing also persisted between Motronic and MS3, even though I have a completely different fuel rail and injectors.

Rebuilding an engine will definitely (probably) net me a good, running engine, but it bothers me that this isn't adding up.