I own a 1.6l Petrol 05 Plate Mazda 3 with just under 60,000 miles on the clock that over the last few months has been causing a few headaches:

Recently whilst waiting at lights or in traffic jams I have found that the engine seems to be vibrating a lot more than usual, to the extent that at times it feels like the engine is about to stall, this occurs whether the car is in neutral as well as it's in gear with the clutch depressed. Whilst I've owned the car for nearly 2 years I've only really noticed this over the last 2 months or so. Sometimes it's fine and other times you can feel the car moving quite violently under the load, not a dissimilar feeling to being out at sea on a small boat bobbing around. Whilst this is happening there are no unusual sounds coming from the engine other than it sounding like it's 'searching'. Its got to the state where the headlights now occasionally flicker whilst it is doing this. I had the alternator changed over Xmas as that was making a noise, when the mechanic replaced it he told me that the bearings were running out of alignment, the recent vibration is making me wonder if I've only just noticed the car does this or whether it is a new fault? Some ideas I have had are that if its got an exhaust gas re-circulator then it is becoming sooted up? Open to any other ideas though. Car seems absolutely fine once it's past 1500 revs and I cannot detect any other signs of faults such as slower acceleration or a lower speed to revs. Engine temp is steady at around 1/3 the limit of the gauge.

Anyway, to further complicate matters as I was driving up the M1 on Friday my ambient temperature reading displayed on the dash vanished. It re-appeared occasionally on the drive back earlier, but reading ambient temperatures of between 0 and -12C, which is very inaccurate. I'm thinking that if the thermometer is a thermocouple there may be a loose connection not passing enough current to the guage. Does anyone know where the outside air temp thermometer is located so I can check the wiring husbandry? If it is a loose connection I'm wondering if its related to the vibration issue?