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Discussion Starter #1
Hoping the collective can help. What is the connection to a worn glow plug and low compression in the same cylinder?

Background:
99' Jetta 1.9 ALH, 120K largely city driving
new turbo at 80K
timing belt at 110K
runaway...seemed to stop with key off, restarted and limped home
car sitting for 60 days
compression test cold with intake/turbo off: 490, 480, 350, 500 (4-1)
VNT actuator stuck
no major oil in turbo and intercooler
10-15mm of soot on intake ports and egr
glow plugs replaced in Oct '09
all but one, in low compression cylinder, look good (attached image)

Does it make sense to pull the head to see if there is piston/cylinder damage? Is this reasonable for a newbie given correct tools (timing belt)?

Are the other tests that might identify the problem?

Do those compression numbers make sense on a cold engine with intake removed?

Rebuild or replace with used?

Thank you
 

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I know that a sticking injector can cause melting of the piston. I don't know if it could melt the glow plug like that.
 

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It's not that hard for a newbie since there is decent room in the engine bay. There's a writeup in the FAQ with step by step instructions.

When you pull the head, measure piston protrusion. That will tell you right away if a rod is bent. There wasn't much oil in the intake or intercooler which raises the question of how and why did it runaway? Maybe whatever oil caused the runaway was quickly burned up. I would do further investigation because of the melted glow plug. Please post a follow up with any findings.
 
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