P0300

99' Explorer Limited V8

A few days ago I was impatient and got on it really hard. It started
missing as I let off. When warm at idle there is an occasional miss but,
when driving it is more noticeable especially when accelerating. I went
to 'Zone' and another place and had it read (CEL is on) and it had code
P0300, "random/multiple cylinder misfire detected".
What are the most probable causes??

Thanks,
Dave
--
Diving is life! The rest is just details.
W.W.W.I.

The usual experts did not chime in, so I will offer my two cents:
Ultimately you will get a code identifying the misfiring cylinder, but don't
wait that long. The catalytic converter may be damaged by then.
Most common seem to be ignition problems. Does the '99 still use high
voltage wires? Are they the original, 9 year old ones? If so, replace them
without thinking twice, even if the problem is elsewhere.
If that's a COP (coil on plug) system, there are tons of stories about
failed coils and, more often about failed 'boots' that connect the coil to
the plug.
Also google the archives of this group (always a good idea).

"Dave" > wrote in message
thlink.net...
> 99' Explorer Limited V8
When warm at idle there is an occasional miss but when driving it is more
noticeable especially when accelerating. I went
> to 'Zone' and another place and had it read (CEL is on) and it had code
> P0300, "random/multiple cylinder misfire detected".
> What are the most probable causes??

Happy, thanks for the ideas! I fixed it two days ago. I didn't report
back here cuz' no one seemed interested.
My brother in law was coming here (about 150 miles) with the tools to
replace the plugs, for the second time. Last time I bought plugs and
wires just to know when they had been changed. The wires looked new and
we pulled a couple of plugs and they looked new! The vehicle had 100+k
miles when I got it 15K ago. Before he got here I put the front end on
stands and took off the tires. While waiting for him I took off the
soft, lower part of the wheel well liner on the passenger side. That
wire has a metal shield and as I touched it, it moved! Then I plugged it
back on, put the tires on, lowered the vehicle and drove it to return
the new plugs. Nice smooth ride....
I love my Explorer again!!!

Dave

Happy Traveler wrote:
> The usual experts did not chime in, so I will offer my two cents:
> Ultimately you will get a code identifying the misfiring cylinder, but don't
> wait that long. The catalytic converter may be damaged by then.
> Most common seem to be ignition problems. Does the '99 still use high
> voltage wires? Are they the original, 9 year old ones? If so, replace them
> without thinking twice, even if the problem is elsewhere.
> If that's a COP (coil on plug) system, there are tons of stories about
> failed coils and, more often about failed 'boots' that connect the coil to
> the plug.
> Also google the archives of this group (always a good idea).
>
> "Dave" > wrote in message
> thlink.net...
>
>>99' Explorer Limited V8
>
> When warm at idle there is an occasional miss but when driving it is more
> noticeable especially when accelerating. I went
>
>>to 'Zone' and another place and had it read (CEL is on) and it had code
>>P0300, "random/multiple cylinder misfire detected".
>>What are the most probable causes??
>
>
>


--
Diving is life! The rest is just details.
W.W.W.I.