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Re: [T3] Diagnostic help: Loud popping...Āvalve problems?


On Mon, 2002-07-08 at 09:13, ICBM Webmaster wrote:
> Here's the story:
> Me and my girlfriend are merrily driving along in my baby.  We enter a
> tunnel and she wants me to rev the engine (it's LOUD in the tunnels) so I
> oblige.  When we leave the tunnel there's suddenly this loud popping sound
> coming from the exhaust.  I mean LOUD, like backfiring.  I have
> acceleration, but it's not as powerful as normal now, and there's the
> backfiring.  The engine backfires at idle as well.  Only under very, very
> slight throttle does the backfiring stop (from what I can hear).
> Battery is good, all four plugs are firing, valve lash is correct, rocker
> arms and push rods move (I rotated the engine 'by hand' and watched them all
> move).  Distributor cap and rotor are in good condition, Pertronix
> electronic points (those either work or they don't, no inbetween I've ever
> heard of), new plug wires (all passing spark, I have a timing light and
> 'engine analyzer' that gives rpm and flashes an LED every time the spark
> fires).
> My next guess is...I $ hate $ to $ even $ think $ it $...compression check
> the cylinders to find the side with the burned valve/dropped valve seat. 
> Suggestions?  Remember, bored and stroked 2007cc w/8:1 compression, 40mm
> Dells.  More info at http://www.icbm.org/erkson/personal/VWSTATS.HTM
> This is a fairly new engine, just broken in last year (dino oil, no
> synthetics) and not driven much.  Help!-- 

If there are no mechanical noises, I would guess right off hand that
maybe you broke an exhaust valve spring, of bent an exhaust valve.
-- 
Russ Wolfe
'66 FB MT (It drove)
'71 FB AT 
'65 Bug (not running)
russw@classicvw.org
http://www.classicvw.org



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