Spark Plug Extentions

[Scuba Joe]

Hi all,

I have seen posts on other models about the spark plug extenders on an S3 (non cat). I have replaced the dizzy cap, rotor arm and leads but haven't as yet been able to source the plug extenders.

Do these have any use? Obviously the metal shield required the plug extenders, but If I ditch the shield and plug extenders are there any negatives to this? I am sure they were originally put on for a reason, but I cannot see what the reason is!

Many Thanks in advance.

[RayTVR]

Do you mean the extenders that plug into the HT leads at the distributor end?

If so I believe that they are there to help with suppression radio frequency interference. I still have them but am also considering ditching them, most cars don't seem to have them.

[GreenV8S]

As far as I know, the main purpose is to get the leads further from the exhaust heat.

The ignition system would have been designed to have a certain resistance on the HT circuit and would usually have either resistive plugs, or resistive leads, or resistive plug extenders to achieve this. If you have resistive extenders with non-resistive plugs and leads then the resistance of the extenders is important - but it could be replaced by using resistive plug/leads.

[RayTVR]

Think the Rover V8 has extenders at the plug end (as you say to shield the leads form the heat) - S3 doesn't have these.

[phillpot]

That big tin can thing round the dizzy cap and the extenders went in the bin years ago, no apparent adverse effects yet

[Scuba Joe]

RayTVR said:

Do you mean the extenders that plug into the HT leads at the distributor end?

If so I believe that they are there to help with suppression radio frequency interference. I still have them but am also considering ditching them, most cars don't seem to have them.

Yes, this what I mean.

[Scuba Joe]

phillpot said:

That big tin can thing round the dizzy cap and the extenders went in the bin years ago, no apparent adverse effects yet

That's good to know. After replacing the leads etc and having disturbed the extenders I seem to have developed a very inconsistent idle with the car nearly stalling, then picking up to about 1200rpm, then nearly stalling again etc etc, but only when warm. No loss of power elsewhere, but the only thing that has been fiddled with is the leads cap and rotor and the new ones are definitely right. I'm thinking that disturbing the extenders has given a loose circuit somewhere in the HT area.

[mk1fan]

Simple check would be the coil too as it might be breaking down when hot.

Are the bullet chaps on the top of the spark plus properly screwed on and are the HT leads pushed properly home?

These work well to help protect the HT leads and plugs from the TVR manifolds.
http://www.ebay.co.uk/itm/8-Pcs-Practical-Black-Ca...

[Scuba Joe]

Thanks! Is there a simple check you can do on the coil without purchasing a new one?

[Oldred_V8S]

Scuba Joe said:

Thanks! Is there a simple check you can do on the coil without purchasing a new one?

Wrap a pack of frozen peas around it or check the resistance when it starts to fail. I would relocate the coil if it is mounted anywhere on the engine. We did this on one of the S-Club tours and it cured the misfire.

[Scuba Joe]

Update:
Tried to fix the fault today, so firstly I wiggled all the terminals on the extenders, and the leads including the coil, then checked other sensors I could see in the engine bay with a wiggle test (just in case), then ran a diagnostic with a Gunson Fault reader. After all tests, there are no recorded faults in the ECU or in the last 40 odd starts.
So, I drove the car for a number of miles today and the fault has miraculously disappeared - running like a dream! so I am back to either dodgy Extenders, or thanks to other comments, a coil on the way out. Next steps, get rid of the tin can and plug extenders, possibly change the coil just because its the one thing not yet replaced.

[yknot]

Ignition problems won't show a fault code in the ECU so I would guess you have a dodgy connection somewhere. First thing I did when I got mine was to change all the ignition components as I had no history of when the bits had been changed and the dizzy (complete with the metal shroud and extensions) looked original!!!