My Voyager is backfiring in the aircleaner at 3700-4000 rpm when i
drive it and if the gearbox is in park and i rev it up to the above
rpm. It starts to missfire slightly and if i press the gas even more
it will backfire so much that i even blown a aircleaner top off. This
happens almost everyday but sometimes it will run perfektly. I´ve
changed wires and plugs whith no change.
There is no error code in the "check engine lamp" only 55.

Is there someone that can help me, i´m going crazy over this.
I´ve read a lot about mis/backfiring here, but nobody seems to have
exactly the same problem as me. meaning at a specific rpm regardless
of load/uphill/downhill/decelerating/in-gear and so on.

Help please!!!!!!!!

Janne

Solution:

The CPS sensor (crankcase position sensor) was to close to the
flywheel, and due to
vibrations at the mentioned rpm it was thouching the flywheel and give
the computer
rubbish to work with. This resulted the ignition coils to send power to
the sparkplugs
at random, creating the hopeless backfiring in the aircleaner.
I just removed the sensor, cleaned it up a bit because the plastic body
had partly covered
one of the two brass pickups on the sensor. Put it back in the hole to
the bottom, and pulled
it back 0.098 inch  (2.5mm) and fastend it.

And it works like a dream again!!.

Janne