i have developed a misfire under load.
It had a intermittent misfire at 1700 - 2500 rpm which developed into a constant misfire under load.
but if i feather the throttle and gently accelerate seems like its not misfiring but as soon as i put any load on the engine it misfires.
it has 146,500 miles on clock

any ideas!?

many thanks

 

Distributor cap and rotor would be my first bet; have they been replaced in recent history?

Also plug wires and plugs too if they haven't been replaced in last 60K miles or so...

 

thanks as far as im understanding the plugs and wires have not been changed will try the distributor cap and rotor arm with the plugs first

 

gdog have to say many thanks dude
changed plugs distributor cap and rotor arm and its running perfectly

 

Good deal!

Missing under load is classic symptoms of secondary ignition breakdown; most likely place is plugs and/or dist cap.

 

Hi there,
I have had exactly the same problem with my 1997 850 2.5. Replaced plugs, rotor arm and distributor cap this afternoon. Initially ran fine, then started to miss intermittently under load, excliuding coil now thinking blocked fuel filter??
Any ideas??

 

Sounds like someone needs a tune up

Just a side note, I was helping a friend with their S40 that was misfiring. Pulled the plugs and the gap was .054....stock is .028.