Anti Theft Switch

[saljo]

Hi,

I have recently started to experience an annoying misfire/flat spot at around 2,500 - 2,700 rpm.

All the usual suspects have been checked. ie, plugs, points, rotor, distributer, leads etc., also Stromberg dash pots, air leaks, diaphram but with no luck. I suspect the anti theft device maybe the culprit and am tempted to disconnect. Is this as simple as it sounds, or are there any other implications I should consider?

Any help/advice much appreciated.

Saljo. Elan Drophead S4 S/E - since new.

[gjz30075]

Hello and welcome. It's not that easy to disconnect, but not hard. Simply cut the wires going to the switch and splice them together to eliminate the switch altogether. You might also work some cleaner spray in the switch while working the switch to clean the contacts.

Greg Z

[hatman]

You could do what I did with mine and bridge the connections at the back of the switch with solder so that the ignition feed is always maintained but, with the switch in the off position, the horn still sounds if anyone (you, when you forget to switch it back on for instance) tries to start the car. At least then you will hear your Maserati horns disappearing up the road as the (deaf, I imagine) thief drives away.

[Chancer]

Did all S4's have this switch? I am not aware that mine does, where would it be located and how does it operate please?

[oldelanman]

Did all S4's have this switch? I am not aware that mine does, where would it be located and how does it operate please?

It's a simple double pole slide switch located in the glove box at the back on the RHS. All it does is break the ignition LT circuit and earth the horn. So when you turn the ignition key the engine won't start but the horn will sound.

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[saljo]

Many thanks Greg Z & Hatman for the info.

I joined ignition wires at the switch as suggested but regret no difference in flat spot/surging - so it aint the switch.

It's odd as it's a recent development and in the rev range I use the most; 2,250 - 2,750 or 45 - 55 mph. If I floor the accelerator at these revs it picks up smoothly it's only with gradual pressure on the loud pedal that surging develops. Any ideas appreciated.

Thanks,

Saljo.

[oldelanman]

As you have Stromberg carburettors my guess would be worn needles and jets. The needles are spring biased so they wear on one side and also tend to ovalise the jets over time. This would lead to an over-rich mixture at constant part throttle which might be what's causing your surging.

[elansprint71]

As you have already discovered, this switch can be an annoyance but not a cause for the symptoms you described.
Whatever; you are better off without it.

[naleder]

So thread dredge I know.

My car has the switch. For years I've found you have to flick it a couple of times before it will start. It's occasionally loosing all electrical as you drive along. Like just complete ignition lights out and then it goes again.

Does that sound a bit typical?

[saljo]

Hi,

Roger was right. New needles and jets resolved the surging and greatly improverd tickover.

BTW needles very hard to find now.

Cheerd,

saljo. S4 Drophead.

[oldelanman]

Hi,

Roger was right. New needles and jets resolved the surging and greatly improverd tickover.

BTW needles very hard to find now.

Cheerd,

saljo. S4 Drophead.

Glad your problem was resolved. Thanks for letting us know, it's useful information for others who may have the same issue.

[oldelanman]

So thread dredge I know.

My car has the switch. For years I've found you have to flick it a couple of times before it will start. It's occasionally loosing all electrical as you drive along. Like just complete ignition lights out and then it goes again.

Does that sound a bit typical?

Not sure I understand your problem. Are you saying that you lose all electrics when driving along or just that the engine cuts out ?

If it's just the engine cutting out then yes that could well be ant-theft switch which you say has been playing up when starting for a number of years anyway. I suggest you remove it.

If you are losing all electrics when driving I would check battery connections are clean and tight and the main earth connection in the boot is good. Also check the main feed from the solenoid to the control box in the engine bay (thick brown wire) you may have a loose connection there.