I've just taken my Hijet in to a Daihatsu garage for a scan as the engine management light was on and it was misfiring and cutting out (when running on both LPG and petrol).

The scan came back with code 36 - Random/multiple Misfire Detected. The garage have tested spark plugs and coils. Both are fine. They are now proposing to tighten the tappets. They are 90% sure that this is the problem. They say it is quite a big job and will cost £140 + VAT.

Can anyone offer any advice relating to this please (baring in mind that I know little about the topic)?

Does this sound like a reasonable price? My biggest concern is that they will tighten the tappets which will not fix the problem and I will be over £140 out of pocket. Any advice would be gratefully received.

Many thanks