Quarter mile runs & now misfiring

devonutopia

Top Post Dawg
Joined
Dec 1, 2003
Location
Devon, U.K
TDI
PD300 Skoda Fabia
More quarter miles yesterday. New venue and surface not quite as good for launching but despite 2.4 to 2.5 60 foots I had a 13.5 quarter @ 116mph.

Thing is when I was near home, the car started misfiring..... Sounds like this

https://www.youtube.com/watch?v=vOhDyYU0pNM

This morning I did a log of group 13, (to follow) I am wondering if its perhaps the PD wiring loom? It "feels" electrical but of course may have to whip off the cam cover to check the condition of the cam.
 
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TDIMeister

Phd of TDIClub Enthusiast, Moderator at Large
Joined
May 1, 1999
Location
Canada
TDI
TDI
Cracked piston(s)? That's my guess.

Edit: Log cylinder IQ balance (is that 13? Been a while) and report.
 
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Fix_Until_Broke

Top Post Dawg
Joined
Aug 8, 2004
Location
Menomonee Falls, Wisconsin, USA
TDI
03 Jetta, 03 TT TDI
Pull off your oil fill cap while it's running - if you get a gyser of blowby and a strong pulse in time with the miss along with excessive white smoke out the exhaust at idle, you've likely got a broken piston. Been there, done that, didn't get the t-shirt...



From what I can hear in the video, it sounds mechanical - never misses a beat (pun intended), follows engine speed exactly. If it was electrical, I'd think it would be a bit inconsistent or change with load/RPM/etc.
 

devonutopia

Top Post Dawg
Joined
Dec 1, 2003
Location
Devon, U.K
TDI
PD300 Skoda Fabia
Well, I took off cam cover and all well underneath. Refitted and went for a drive and everything back to normal. Very odd! I was chuffed until the engine warmed up properly and the misfire returned.... At least now I know its just a "warm engine" thing. I plugged in VCDS again and this time got a cylinder 1 electrical malfunction fault, so I am changing the injector wiring loom asap. Needs to be quick as I am on a trackday in less than 2 weeks time!
 

moivw

Veteran Member
Joined
Nov 5, 2011
Location
France
TDI
Séat ibiza(s): ahu and pd100
try to check if the wire is not simply unplugged from the injector first
 

shadowmaker

Veteran Member
Joined
Jan 30, 2007
Location
Finland
TDI
2.5TDI
My -04 Passat did this only when warm. Just cleaned and retightened those four injector connectors inside camcover. No need to change the whole wiring loom.
 

chapelhill

Veteran Member
Joined
Aug 19, 2005
Location
Scotland
TDI
03 Ibiza pd13- 2260vk Turbo etc.., Merc E280cdi
Make sure none of the injector hold down bolts has come loose, can give similar symptom.
 

devonutopia

Top Post Dawg
Joined
Dec 1, 2003
Location
Devon, U.K
TDI
PD300 Skoda Fabia
Yeah me too. I have a low mileage loom coming from a newer car, so I am hoping that solves it. Would rather change it. I did push down on each connection whilst I was fiddling, so thought that might have fixed it. Loom should arrive tomorrow.....
 

JFettig

Vendor
Joined
Aug 18, 2010
Location
Blaine, MN
TDI
B5 Passat, 2010 Jetta
That is something you should really get new. They clip into the injectors very well only the first time, then they are loose after they're removed only once.
 

jimbote

Certified Volkswagen Nut
Joined
Jul 10, 2006
Location
spiral arm, milky way (aka central NC)
TDI
Tacoma 4x4 converted to TDI
That is something you should really get new. They clip into the injectors very well only the first time, then they are loose after they're removed only once.
you can take the connectors apart and tighten up the terminals ... my harness is original with over 345k miles and ive swapped injectors three times
 

A5INKY

Vendor , w/Business number
Joined
Sep 4, 2007
Location
Louisville, KY
TDI
2006 Jetta TDI, 2002 Eurovan Westphalia VR6
The connectors are pretty standard spade type and the plastic part unclips easily. Not much of a clip to hold them on at all, just friction from the connection. I too have had the same harness in my car for repeated injector swaps and only tightened the connections once.
 

hatemi

Veteran Member
Joined
Aug 25, 2005
Location
Finland
TDI
Audi A6 4F 3.0TDI
Or you can gently squeeze the connectors tighter without disasembling them. The plastic part is somewhat flexible and you only need to tighten them a tad. Using a file or even a pick to clean the contact surfaces is a good idea.
 

devonutopia

Top Post Dawg
Joined
Dec 1, 2003
Location
Devon, U.K
TDI
PD300 Skoda Fabia
Is there a technique to carefully and accurately unclip the loom from the injectors? I have removed a loom from a head or two, but it's always felt a little brutal, like I was missing something about the way the connection is made to the injector unit..... :D
 

A5INKY

Vendor , w/Business number
Joined
Sep 4, 2007
Location
Louisville, KY
TDI
2006 Jetta TDI, 2002 Eurovan Westphalia VR6
Pull straight up, that's it. They never seem that difficult to me.
 

devonutopia

Top Post Dawg
Joined
Dec 1, 2003
Location
Devon, U.K
TDI
PD300 Skoda Fabia
I know - always easy in theory. Like those damn annoying other wiring connections which have the lever you have to manipulate to release, and usually the lever snaps off before it unclips.... :D
 

devonutopia

Top Post Dawg
Joined
Dec 1, 2003
Location
Devon, U.K
TDI
PD300 Skoda Fabia
As a quick follow up to this, fitted a newer injector loom from a 2007 car end of last week and now the misfire (once warm) has gone. Thanks for all points made in this thread.
 
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