Tmm20

Gently is the exact opposite of how I drive this car. Lol.

FredR

Soot is running rich but remember there are certain conditions where the motor runs rich by design such as warm up and full load power. Often takes a good run to get the pipe back to grey colour.

Blue smoke is oil -no doubt about that.

I am not too familiar with the MAF setup on your model- presumably you can "tune it" a bit to run bit richer or leaner as needed- I know some of the earlier models have this feature but not sure which ones.

On the later models the MAF is non adjustable- Cat models run with an O2 sensor in closed loop mode for the cruise range map. Non cat models like mine run on open loop with an external adjustable resistance pot to adjust the AFR within certain bounds.

GregBBRD

You dismiss every reason for it to have seized....except you believe a piston stuck, out of the blue.

They don't do that.....

BTW....the valve inserts into one of the metal nipples on the passenger side of the filler neck. You don't have to remove the filler neck. Just remove the rear most hose and see if it is there.

Tmm20

I'm leaving to go get the compression tester shortly, I'm really hoping it doesn't end up being a dead cylinder but I don't know at this point. When I remove the oil fill cap while running puff of smoke/vapor come out in time with each firing of the engine.

On the 86 the maf is adjustable within 0-1000ohm (or kilo ohm idk) resistance variable potentiometer that tunes for the c0. This in turn tunes it to run lean or rich depending on the setting. Previous to the incident, 860-ish was my sweet spot to run the car with the best power I could manage to get out of it.

Now that the intake has been completely refreshed, I am imagining that it needed to be so rich/high ohm to offset for huge false air/vacuum leaks just to run right. I just turned the maf pot all the way down to 90ohms. This is something I could have never done before the incident, the car would barely run and had zero power threatening to stall when revved. It just doesn't make any sense.

Tmm20

I asked if I could remove the neck so as to avoid removing the intake again after just putting brand new gaskets on it. There is no way i am getting the hose off and back on without pulling the intake or neck.

I realised after the water bridge was said to need removal that it would end up easier to pull the intake again if I end up needing to verify the valve.

Even if its missing, where am I going to get one? I see zero sources online for them.

Tmm20

Another issue... Won't the amount of oil in the intake literally running down into the cylinders falsify the compression test? Since you're supposed to add oil to the cylinder to check a low value?

hwyengr

Yeah. If only there was another test that somehow checked the ability of your combustion chamber to hold pressure...

Tmm20

Doesn't matter. 25psi dry on #7. Thanks all. That's the end.

hwyengr

Are you at least gonna strip it before scrapping? Figure out what happened For Science?

If you're anywhere near Chicago I'll give ya $250 for the lump.

Cosmo Kramer

Have you pulled the plugs yet? If one cylinder isn't firing right the plug will tell the story.

Something must have been jammed in the combustion chamber to cause it to seize there is no other explanation. Especially when you said it would turn backwards. I've been there with a 928, mine was a stray intake washer that rode in the intake port for 300 miles. One day I shut it off and it dropped in the cylinder when the intake valve was open. Ran for a few seconds and locked up solid. I was able to save mine, I pulled the head and fished it out.

Whatever happened over the course of it sitting must have moved it enough to allow it to turn over. Could still be in there who knows. Let us know the compression numbers (leakdown would be better). Compression can be affected by oil in the cylinders and a cylinder can still produce compression and have terrible leakdown. In my case the washer tweaked an exhaust valve just a few thou but leakdown was 20%.

Edit: I just see that you found the offending cylinder. It must have injested a foreign object and somehow you managed to get it to turn over with it still in there.

Tmm20

There was no foreign object. I cranked the ****ing engine for over two minutes solid running the starter. It seized. It was my fault. People do dumb ****. End of story.

Imo000

You could have ingested a washer like Kosmo Kramer did. The crunch noise was probably a cracking piston and/or a con rod bending. But with the copper shavings tell me the con Rod is bent and the bearing is getting chewed up. Either way you look at it it's game over for this engine.

Cosmo Kramer

If the motor seized from cranking why was it able to turn backwards? Something in the combustion chamber was stopping it from turning clockwise when #7 was at TDC.

Anyways, good luck figuring a path with the car, goodness knows I wish I could turn back the clock on some of my self induced repairs.

Tmm20

Except there was not anything in the intake, it didn't ingest anything, and no one is listening to me having cranked the engine literally until it locked up solid. Outside in 20 degree (f) weather I sat with the key turned and the starter cranking for at least two minutes. The piston seized. If I had a flywheel lock I'd pull it apart just to prove a point.

hwyengr

The hard part is understanding why cranking long would cause the engine to seize. The oil pump is still pumping oil, the water pump is turning, there's no forces from combustion, and it's spinning at a leisurely 300 or so RPM.

Starter motor burning out, that makes sense. But how does slowly turning the engine over for a long time cause it to seize?