TQS judder/misfire

griswold

Registered User
Been having a a juddering for a second or two under heavy throttle, ease off and ok will judder with .5 bar but will go to 1 bar
it happens at various speeds and revs.
When its cold it dosn't happen straight away had full boost and no juddering and car went like a rocket
after a couple of miles started to happen when warmed up.
Waiting to get a pressure test for leaks, checked for visable and tightend hoses.
Changed vac line, diverter valve, put new air mass sensor, coolant temp sender,fuel filter
nothing when scanned.
Think of getting a set of coils? ignition control module?
car seems fine when cold? car 1.8 tqs remapped

Ideas as to why fine cold ?
thanks
 

Bradderz_1988

Dont replace it, Upgrade it !!
Check the Plugs they maybe arcing does it do it at idle at any point ???

Had similar fault with mine was intermittant then after driving it a bit more it dropped a cylinder permanantly so disconnected the coils one by one and number two had dropped swapped the coil to a differant cylinder and it moved to that cylinder so swapped the coil for a good one and was fine after that.
 

griswold

Registered User
Changed the plugs forgot to put that in first post.
Did that show up when scanning your dropped cylinder?
 

aragorn

"Stick a V8 in it!"
Staff member
Moderator
VCDS Map User
Airleak?

Mums A4 was doing exactly this, and it was a split hose on the inlet manifold.
 

griswold

Registered User
Yes the problem started after plug change but thats when i noticed it.
Probably a coincidence?
Changed them for another set too.
I'm thinking airleak but its fine when cold?
 

aragorn

"Stick a V8 in it!"
Staff member
Moderator
VCDS Map User
hers seemed better when cold too, got worse when it was hot.

It was fairly random, mostly occurred at medium to large throttle openings between 2-3k or so. If you got it upto ~4k and gave it full throttle it would often take off at full boost with no trouble, which should have been the tell tale that it wasnt ignition related. I didnt find the airleak until after swapping everything ignition related, and the MAF though.

Was one of the small bore hoses that goes to the tank vent valve or something, had split underneath and you couldnt really see it.
 

griswold

Registered User
Thanks, i was hoping the hot/cold running would help identify the problem.
Maybe as the engine heats up the pipes warm up and the leak is worse.
Would be great if it was just a leak and i could find it.
Aragorn would be great if you could help identify the pipe or location where you had the split
 

aragorn

"Stick a V8 in it!"
Staff member
Moderator
VCDS Map User
to the right of the throttle body a hose comes off then turns 90degrees and snakes off to either the bulkhead or breather thing (cant mind which)

It was that hose that was split.
 
Top