My 1999 4.0 V8 (almost 50,000 miles) was coughing under load at low
revs (1500-2000) and I suspected a coil pack. Checked all and they
were about 1.2 ohms each. I found lots of oil in the plug port of
the driver’s side bank cylinder no.2 - is this a rocker-cover
I decided to get all the plugs out. Shock!! horror!!
They were all in a terrible state! Signs of:
- Combustion gas leaking up the porcelain (a tide mark around the
- Corrosion on the spark-plug body (external) due to water ingress
into the port (those pesky covers are next to useless and allow
water in from underneath);
- Corrosion on the cylinder end of the plug, where the spark jumps
I got them all out, cleaned as best I could, refitted and Hey
Presto! a very happy motor. I think all cylinders were firing, but
not very well. So my message is, do not wait for 70,000 miles or 7
years, get them changed a lot sooner.
To get the covers off you need a tiny 7mm socket and lots of bendy
attachments to release the 6 screws on each side. The coil packs
have a 7mm screw to hold each one. The connection of coil to plug
is by a flimsy spring through a rubber tube, and looks like the
slightest misalignment would make it fail. But is seems to work.
You need a very slim 10mm spark plug socket (3/8 drive, because
1/2’’ drive socket is too fat to go down the hole) and again, many
different extensions, knuckle joints and ratchets.
Also, break every joint in your hand before you start and chop your
socket set into little pieces, because that’s the only way to get
to the damn things! Nightmare job, took me over 2 hours to do all
8, but the results are well worth the struggle.–
Sheffield, South Yorkshire, United Kingdom
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