Black deposit around plug and odd idle

Rowley Birkin QC

Changed the plugs in my car last night, it's recently been serviced and timing belt & wp done but I didn't get around to doing the plugs at the time. Anyway there was a black deposit built up around one of them that I had to scrape away with a wire beore I could get the plug out.

Removed the plug and the threads were covered in this sooty deposit. Anyway I put in the new plugs and the car is idling at around 1500-1800RPM even after reaching operating temperature. Another thing that I notice is that the revs are generally higher through the gears than what they would have been before at similar speeds.

It's a 1.6 16v Opel Vectra B. Any diagnosis/observations/remedies? Suggestions involving matches and gallons of petrol are not welcome, I know it's a shed but all I can afford at the moment.

Cheers.

woop

did it have this problem before you put in the plugs?

does it idle high just after you start it or a while after?

is there any dash lights on

Ive got a theory but just want to wait

ART6

The deposit around the plug and on the threads sounds like a loose plug that was letting gases past. The high idle might be a faulty Lambda sensor (I am no expert on Opels, so that could be wrong). Maybe if the two were combined -- a loose plug and a duff Lambda allowing too rich a fuel air mixture, perhaps the gases escaping past the plug and resulting in the compression of one cylinder being down a little could hide the Lambda problem? I had a Sierra some years ago on which one plug came loose after a service. It wasn't obvious in any way and there was no extra noise. I only found out about it when the bloody thing blew out completely.

woop

ART6 wrote: »

The deposit around the plug and on the threads sounds like a loose plug that was letting gases past. The high idle might be a faulty Lambda sensor (I am no expert on Opels, so that could be wrong). Maybe if the two were combined -- a loose plug and a duff Lambda allowing too rich a fuel air mixture, perhaps the gases escaping past the plug and resulting in the compression of one cylinder being down a little could hide the Lambda problem? I had a Sierra some years ago on which one plug came loose after a service. It wasn't obvious in any way and there was no extra noise. I only found out about it when the bloody thing blew out completely.

plugs dont just become loose that often though possible
and he changed them so thats not a problem anymore

do the cheaper things first-clean youre icv and give the lambda a wipe, do these seperately so you know which one improves it if so

a sensor perhaps crankshaft

youve got no other problems with the car at the moment though?

paper clip test might throw up something

Henry Ford III

bigkev49 wrote: »

....Another thing that I notice is that the revs are generally higher through the gears than what they would have been before at similar speeds....

Clutch slipping. Gear ratios/speeds are fixed otherwise.

Rowley Birkin QC

woop wrote: »

did it have this problem before you put in the plugs?

does it idle high just after you start it or a while after?
is there any dash lights on?

Ive got a theory but just want to wait

Nope, just since I changed them last night.

High idle seems to have cured itself

No dash lights.

woop wrote:

youve got no other problems with the car at the moment though?

paper clip test might throw up something

No, no other problems.

Paper clip test?

HF III wrote:

Clutch slipping. Gear ratios/speeds are fixed otherwise.

My first thought but it seems a bit coincidental given the state of the plug that I removed and the deposits that I loosened. Was wondering if any of this residue that might have dropped into the cylinder would cause any of the problems.



Cheers for the replies lads.

Rowley Birkin QC

Shameless bump.

Any more theories out there? Anyone have any views on Redex?