My S3 has developed a couple of problems - I'm not very mechanically minded and I don't really know anyone over my way to give me advice.
The 2 problems are that
a) my car is difficult to start - the battery does not seem to hold it's charge
b) once started the car idles unevenly and if the revs are increased the exhaust note sounds like a trails bike or a revved moped.
Background - 3 year old 125 Sigma Roadsport - 15 months ago upgraded by CC to 150. The car ran really badly in traffic at low revs (kangarooing), CC could not resolve it and said that was how they all ran. At the suggestion of several club members I took it to the 2 Steves for a remap last June. They made it run significantly better. The car has generally run well and done several long trips. In the winter I take the car out if the conditions are ok just to keep things ticking over.
Mileage 11.5 K - car fitted with battery master switch to avoid battery drain (no power in garage).
In April I went up to Wales and then went to the Isle of Wight Blat - no problems. 10 days after the IOW I did a pre MOT check on the car - everything AOK. The next day - the test day the car would not start. I had to reschedule the Test for 05/05/2011.
Managed to get the car running - seemed quite a lot of fuel in the system. A fair amount of dirty vapour came out of the exhaust. I let this burn itself off, took it round the block. It started first time the following day, I took it on a 60 mile round trip to get the MOT - no problems.
Due to work pressure I was not able to use the car for a couple of weeks - again it would not start - I got a friend to start the car with a powerpack and had it running up to working temperature but the battery does not seem to be holding it's charge. While running at working temperature it gave a reading of about 13.4 V but it would not restart without the leads. Took another reading with the engine off and it was down to 10.4 V.
More alarming is the noise I am getting if I put my foot on the gas, it sounds like a trials bike or a highly revved moped - I did not dare take it for a spin in case I would inflict damage to the engine/exhaust system.
When it initially fired up there were coughs and splutters and after a while the odd intermittent faint burning smell and the odd small pop from the exhaust. I thought the initial fuel or condensation that was in system would have burned off but the character of the exhaust note did not change.
I can imagine the battery might be past it's best even though it is only 3 years old. I have tried my best to keep it running at regular intervals but it has gone for longer periods in the cold months where I have not had a problem with the battery - it would always start first time.
The car sounds like it is running unevenly, I don't know if it could be an exhaust related issue. The car was running well in April and it covered about 1,000 miles.
Any advice would be greatly appreciated.