Ignition problem - but cured by re-starting the car ?!

[Troogly]

Hi

I've had an odd problem, which is intermittent, and generally occurs on the very warmest of our sunny days. Suddenly the car will lose most of its power, but won't cut out. Very lumpy tick over. Doesn't really pick up when any throttle is applied. Generally in poor shape and sounds it too. So I pull over, cut the engine, re-start the car and everything is fine again. This can go for days without a problem occurring or can happen twice in 15 mins. It does seem to be ambient temperature related ....

When it runs fine, it really is fine - no obvious problems.

Any thoughts on this one?

Thanks all

[kamacasininja]

Could be an alarm/immobiliser problem.

Do you hear your fuel pump prime everytime you turn on the ignition just before you fire up?

I have a Toad alarm on my car and if I shut off the alarm and take longer than about 20 seconds to start the car it will 'immobilize' the car, after about 1 minute it will lock the car and go on to set the alarm.
However, in between those times what I find is that I can turn the key (first thing I notice there's no sound of the fuel pump priming) and the car will start but sound bloody awful and be pretty much undriveable (as with your symptoms).
I too have to shut it down but I hit the alarm disable button again so that next time I hear the pump prime and it'll sound proper sweet and run like it should.
Obviously, as far as I'm conscerned the starter shouldn't even kick in let alone the engine start, and I imagine it'll cut out after a few seconds but there's definitely something amiss with the immobiliser part of my alarm so I'll be replacing that.

I wish you well.

[Toffer]

Coil?

[Troogly]

Thanks all. Well I think it could be immobiliser related. I've got a voltmeter across the fuel pump and when this intermittent problem occurs the voltage drops right off. This could explain the rough running before the motor finally cuts out. I'm going to investigate this - but just hope its a case of looking at the immobiliser rather than anything more sinister (ECU related ?)

[Derek Smith]

http://www.rv8r.co.uk/misfire.html

Some ideas. And also consider a malfunction of the ignition amplifier.

Derek

Edited by Derek Smith on Monday 19th July 09:35

[Loubaruch]

Could be many things. As you have established that the fuel pump is not operating under fault conditions it could be:

1. The fuel pump itself, these can be intermittent especially if its fairly old but as there are no volts to it this would seem very unlikely.

2. Either of the two metal cased relays that operate the fuel pump. Located in the mess in the passenger footwell, both Bosch relays have rectifiers in series with the coil to protect the ECU, not unknown for incompatible relays to be fitted.

3. Could be the immobiliser.

If you wire the fuel pump directly from an ignition feed that would at least narrow it down and prove the pump.
The relays are inexpensive (about £25/pair from TVR dealer)so worth keeping spares anyway as they are not that common.
Lastly you could trace the immobiliser circuit that isolates the pump and bypass that.
Best of luck!

Edited by Loubaruch on Sunday 18th July 22:21

Edited by Loubaruch on Monday 19th July 22:01

[Troogly]

Thanks both for your suggestions. Very helpful. I'm currently going down the relay & ignition amp route and hope by a process of elimination I can clear this problem. If these don't work - next stop immobiliser I feel!

Thanks again - this once again proves how valuable the PH network and Griff forum in particular really is.

I'll let you know how I get on...