Plugs 1&2 black

Vectra 1.6 Preg 1600 cc 16v 140K



I look after a neighbours' Vectra about 4 months ago I carried out a service
and replaced the following. Air filter, oil filter, oil, fuel filter,
cambelt, sparkplugs. Also I used flushing oil which seemed to quieten down a
noisy top end.

2 weeks ago she went 200 miles away on holiday in car. I received a phone
call from her on the return journey, she had been travelling on the motorway
at about 70mph for an 1.5 hours, she left the motorway on the slip road
,slowed down and then attempted to accelerate away, however the car had no
pull and just managed to limp into a layby. When I got to the car and tried
to restart, it appeared to be only running on 3 cylinders and seemed very
noisy from the top end. The vehicle was duly recovered. About 3hrs later.
The recovery guy said it could be the coil. When I restarted the car, it
appeared to run on all four, but still noisy, bit like tappets. I removed
the spark plugs and found that 1&2 were black but 3&4 appeared near normal.
I carried out a compression test and all 4 cylinders were ok and about the
same reading. I cleaned the plugs and took the car for about a 10 mile
drive, the car pulled well up steep hills and appeared to run ok, maybe a
trace of hunting on at idle. Removing the plugs again showed that No 1 was
black again with 2, 3,and 4 ok



I don't think any fault codes have been logged as the engine management
light has not come on.



Anyone have any ideas,



Thanks for reading this Howard

 

No special insights on this model.
On general principles; black plugs can be caused by
1) oil past the rings on one or more cylinders (with low compression
readings) -or-
2) A flaky spark due to a leaky plug lead, a flaky coil, especially on
multi coil ignitions, a poor ignition module (but less likely).
Round here, you can buy a gadget that puts a screw adjustable spark gap
between the lead and the plug - a weak or missing spark shows up with
this deal. -or-
3) These days, owith multi port injection (one per cylinder) a leaky
injector.

#3 is expensive, and #2 is not so dear....

Brian W

 

I have checked the HT side using a device that you insert in the plug lead
and allows you to increase a gap that the spark has to jump accross. Also
this car has two coils one for 1&3 and other for 2&4

Thanks Howard

 

Could try swapping coil positions. It might even be possible
to swap plug leads 1&2 to 3&4.
This might be a heat sensitive fault as ignition problems sometimes are.

Brian W

 

Yes, a good point, as recounted somewhere in this newsgroup I had an
Omega with a dodgy HT lead which only showed up when it was at running
temperature.