Slight Misfire (electric related??)

:confused: I have a 2.3 inj 245 - anyone experienced this problem/feature - when driving along and you switch on the headlights - there is a slight misfire/hesitation at the same time as you flick the headlight switch?? - sometimes happens when you turn the heater blower on too ?? - not a major problem but just wondered if anyone has the same and if so what causes it - any cure ? Thanks Andy

Hi, apologies my technical knowledge is not that detailed, from reading the haynes manual I would say it has either the LH-2.4 or LH-3.1 fuel injection but cannot see how you identify which is which? - it was registered in Germany in 1991 and is badged a 240 however it is very similair to the UK GLT, alloy wheels etc - the engine is a B230F according to the sticker on the side and the VIN no is YV1245883M1905713 - any help would be appreciated, thanks Andy

I would suggest cleaning fuses 11 and 12, although I can't see how the blower would affect it. The fact it happens instantaneously suggests ignition to me - but I've no doubt you'll get plenty of other suggestions!

Misfire. 

This is a known problem (Volvo) and there was a bulletin and fix for this. If I remember correctly there was a design fault on a circuit or relay which caused the injectors to lose their earth momentarily when there was a moderately large current draw on a particular circuit. My 240 (same model year engine etc) used to do it when I used the accessory fit air horns but I think the original symptom used to appear when the headlights were switched on while driving (also did this on mine). I remember researching this many years ago and if memory serves the fix was to replace a couple of relays one of them being the headlamp step relay. Because of the expense of the parts and the infrequent nature of the fault I never bothered to fix it and never had any problems relating to this in the twelve or so years I had the car. In short I would not bother or worry about it. For your info from the vin no. 1991my 245 with B230F (LH2.4) with M47 5speed manual gearbox. Regards, Paul.

Both, thanks for the advice and info - as you say Paul it is not really a problem - more of a "quirk" so I will leave well alone, once again many thanks Andy

Mine has always done that a little bit (93, LH 2.4). Despite careful tracing of every single earth point and electrical connector, nothing made any difference. It is most noticeable when idling if the electric cooling fan cuts in. There is a small drop in revs, apparently caused simply by a momentary voltage drop. Possibly the battery was on its way out when I first noticed it - now I hardly notice. It seems it can't be cured, so just has to be ignored.