astra problem

I have a 99 astra 1.6 ls 8valve and recently whilst driving the engine seems
to be misfirirng, then the engine management came on i had the fault
diagnosed which came up with a faulty oxygen sensor this was replaced (the
engine management light no longer comes on) but it has made no difference in
fact the problem is getting worse. i removed the spark plugs to find that
they were very sooty which was by the way the condition of the oxygen
sensor. also the temp gauge never goes above the quarter mark and quite
often drops to zero with the engine warm.
Any help or ideas would be greatly appreciated.
jym.

 

How does the heater perform? do you get good heat out of it early on on a
cold morning? I ask because you dont mention if the heat matches the temp
guage.
thinking maybe dodgy thermostat. engine doesnt warm up at all, so extra fuel
is added -all the time-thinking cold engine/rich mixture. result is sooty
deposits and a lumpy, stuttering motor. (think back to older cars and how
they ran if you suddenly pulled out the choke knob (remember them?)and
richened the mixture.

Mike

 

charge under warranty

 

try cleaning the crankshaft speed/position sensor.