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HELP Lost compression after replacing a coil, plugs, HGV, PCV.

1K views 8 replies 4 participants last post by  soje 
#1 · (Edited)
HELP Lost compression after replacing a coil, plugs, VCG, PCV.

2007 Passat 2.0 TFSI Wolfsburg edition with 160k miles.

Hello,

Short version: Could a frayed edge of a serpentine belt cause compression loss?


Long version:

I had a misfire on cylinder one, which of course made the engine run violently. I pulled the coils and found oil soaked plugs. I replaced the bad coil, all the plugs, the valve cover gasket, and a PCV.

The car ran for a week. Then after a drive, and shutting the car off, it wouldn't start. It was cranking, but making the classic no compression sound. I've learned that this could be a skipped or damaged timing belt, a broken intake cam chain, a broken chain tensioner, a bad cam follower, lack of fuel, and/or other things. I know the valves could be shot now as well. I wonder if all the shuddering from the misfire may have broke a worn out chain.

I noticed the inside edge of the serpentine belt is frayed, but it still appears turning everything that it's wrapped around.

Should I try to replace the serpentine first, or am I going to have to start working through the list of things that could cause compression loss?

I don't have a lot of experience with working on cars, so I appreciate any advice.

Thank you,
 
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#3 · (Edited)
Those videos are where I found out what was going on. I just ordered a fuel pressure test gauge. His videos are awesome, and he lays it out thoroughly. The engine was running so violently when it was misfiring, I wonder if that may have cause the belt to jump. I'm researching on how to tell if the belt has jumped, and how to fix it.

On a separate note, does anyone know of a good OBD scanner to look for? Are the diagnostic computers worth the extra money?

Thank you,
 
#4 ·
Belt fray will not cause loss of compression. You have a broken timing chain. Both issues cause catastrophic engine failure. Sent back the fuel pressure gauge and get either a leak down tester or compression tester. Also, a single cylinder misfire will not cause violent shaking....that was you timing chain jumping its first tooth after the tensioner broke.
 
#5 · (Edited)
I could really use help. The car is still cranking, but not starting. I still need to check compression on each cylinder, but it sounds like all the videos where a Passat has no compression.I still need to check if the plugs are getting electricity or are firing (not sure which).

I forgot to mention that I put a new valve cover gasket on a few weeks before all of this. Could I have over-torqued the screws?

HPFP is working
Timing belt is turning.
I can see the intake cam moving (looking through oil filler)


I have a cheap scanner, but only understand basics. I have a bunch of snapshots of the OBD reader, but the car won't start, so I'm not sure how much data there is.

Would posting these snapshots help anyone to help me understand?

Should I set timing belt to TDC, and check cams to see if they're aligned, or is it too early to o that?

I know this can be annoying to people who know this stuff, but I'm desperate. I bought a POS for the interim, and it's no longer running.































 
#9 ·
compression test results

Ok. Finally got ahold a compression tester. Took out all spark plugs. The kit I rented had a shallow and deep adapter. I tried both. The adapters have a rubber o-ring at the base of the threads I'm assuming I'm supposed to keep that on, when threading it into the plug hole.


Without throttle shallow adapter
Cyl 1 - 10 psi
Cyl 2 - 10 psi
Cyl 3 - 0 psi
Cyl 4 - 0 psi

Without throttle deep adapter
Cyl 1 - 20 psi
Cyl 2 - 20 psi
Cyl 3 - 0 psi
Cyl 4 - 0 psi

With throttle deep adapter
Cyl 1 - 30 psi
Cyl 2 - 0 psi
Cyl 3 - 0 psi
Cyl 4 - 0 psi

Again, I appreciate any help.
 
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