Broken
insulators are caused by excessive heat or pre-ignition, ping. These conditions
can be caused by over advanced timing, lean fuel mixture, or excess carbon
causing increased compression. Unbalanced/worn injectors or small vacuum leaks
can cause some cylinders to run lean. In addition to the compression check, do a
leak down test. better indication of actual condition. Check injector seals and
manifold boots. Carbon build up on intake valves can also cause mixture
imbalance.
Good
luck,
Dennis
Here is an item for everyones interest.
My '87 Westy has been running
crappy for the last few days and
seemed to be getting worse. Backfiring
through the exhaust had me
thinking burnt valve. Yesterday I took the time
to start digging and
find out what was going on. Looked first at the
distributor cap to
find it full of dirt and the carbon seized up in its hole.
Cleaned
the cap, rotor and inners, then stretched the carbon spring and put
the
cap back in place and started up the engine. Seemed better but still
popping through the exhaust.
Removed spark plugs to have a look see
and found plugs at # 2 and # 3
cylinders had cracked and missing
porcelain. What's that all about ? The
colour of the plugs
were good and these plugs Bosch WR7DTC's were put in
22,400 km ago !
STRANGE ! Anyways, I took a compression reading while I had
the plugs out and found #1 - 125 lbs, #2 - 140 lbs, #3 - 120 lbs, #4 - 135
lbs. Not perfect but acceptable for an engine with 350,000 km on the
clock
and original engine. Put new Bosch WR7DTC's in and stated up
the engine and
VOILA ! Running great again !
Found my
oxy sensor not working in the process so unpluged it and
the engine seems
to run fine with it unplugged. But, stumbles at idle with it
plugged in.
Will order up a new one. The one that's in there now is the
generic one from The Bus Depot put in 47,003 km ago.
Cheers
Frank Condelli
Almonte, Ontario, Canada
BusFusion a VW Camper
event in Almonte, June 7-10
'87 Westy & Lionel Trains
Member: Vanagon List, LiMBO, IWCCC & Capital City
VW Club
Vanagon/Vanagon Westfalia Service in the Ottawa Valley
STEBRO/Vanagon Stainless Steel
Mufflers
Frank Condelli &
Associates or http://frankcondelli.com