Running On.... like a diesel

Hey guys… Phil… Andy

Please tell me what could have caused my exige to ‘run-on’ today at the end of my last two sessions at Knock-Hill. The car was very hot and refused to stop when I switched the ignition off… running on for a few seconds of its own free will.

I very much doubt that I have got significant carbon deposits leading to detonation (could I have??). I was running Optimax… and usually do but am not averse to other fuels when weekly commuting.

What should I check… easy things??

he car was okay on the way home when I stopped for fuel refill (Esso Spr BTW) and when I got home.

Possibly with the car as hot as say and then the problem going away when the car was cooler then I would suspect a sticking relay in the ignition circuit.


sounds like they are running too hot and causing pre-ignition…

this can be VERY bad news, you can blow holes in engines like this.


sounds like they are running too hot and causing pre-ignition…

this can be VERY bad news, you can blow holes in engines like this.

Thanks Simon… so is the cure simply to replace them? or is that just treating the symptom?? if so what need I do to properly address it… ?

Any more thoughts guys?? I’m happy with any speculation

check them for colour (imediatly After a track threash, not when it’s been idleing etc)

if they look like they are running too hot, change plugs to a cooler one.

the difference is the lenght of the insulator round the plug tip, the longer it is, the hotter the plug runs, the shorter the cooler.

if you run to cold a plug, it will foul up and start to miss, not start, if you run too hot a plug it will cause pre-ignition.

Really daft Q… are you switching the car off with the lights on ?

My Elise used to run on if the lights were on. The culprit was the cig lighter plug being wired back to front.

Stopped fine if the lights were off.


Thanks - what colour is a plug that’s been running too hot? also I guess you are saying that my running-on problem might be due to plugs that are too hot and therefore I need to change to a cooler one?


No lights on round here…



The ceramic insulator nose around the electrode will be very white if its running too hot - usually a brownish colour - but if you are running the correct grade of plugs why would that be unless one cylinder was running weak ?

Would suggest a change to new ones anyhow and see how it goes … maybe just a duff one

Thanks Andy

I have replaced the plugs - the ones I took out looked okay tho’ if anything maybe a bit rich…but I had been running around (normally) without bother since so i guess the colour check would need to be done immediately after the problem as prof scuffham says.

I’ll see how it goes at the next track day. liked yer video btw.

Does the car shut off on it’s own or do you have to turn the key off again to get it to stop?

My buddy’s 190S has a bad ignition switch and he can take the key out and the car won’t shut off. Luckily, our cars in the States are all fitted with master kill switches.

Meat it shut off itself after what seemed like maybe 2 seconds of running on. I’m pretty sure its not a ignition keyswitch problem 'cause it has only happened twice (at end of my last two sessions at Knockhill)

I’ve been in touch with Champion in an attempt to have them give advice on colder plugs… but they haven’t replied yet.

Is anyone out there using NGK plugs? which ones??

I use NGK BPR 7 ESL.


Dont forget NGK heat ratings go the other way to Champion - so the higher the number the colder the plug …

My buddy’s 190S has only had the problem with the ignition switch three times in a year. FYI