Volvo Repair: volvo 940 starting problems, volvo 940, gazoline

Question
ey roger,

i hope, you can help me with this question. some mechanics already had a
look on it, but until now, nobody could really solve it.

my car is a volvo 940 polar, turbo. european model from 1996. 245000 km.
since 6 months i drive on gas, a stag 300 was put in.

since a few weeks i have starting problems. it happens sonetimes, not always.
the motor turns, but does not start. when i put out the fuse of the lambda
sond(?), it would start, then i can drive. while driving i put in the fuse again. if
i do this three or for times, even this trick doesn't work anymore. somitimes
the motor just goes off while driving on normal gazoline. the candles, that
give the spark(sorry, i don't know the name), are new. first they thought, its
because of a mass cable. they fixed this last week. it worked again without
any problem. but just for a few days. now i have the same problem again.

sorry for my english, i'm german:).

best, phil.

Answer
Phil, Im completely lost on this one.  What is a Stag 300?  The candles I know what you mean.  English lesson for the day.  Spark plugs=candles.  HA.   I know this will be hard to explain but try your best because Ive read this 10 times and dont know what you are trying to say.  Roger