My vw polo 1.2 52 plate 9n1 has the engine warning light come on. It sometimes missfires when trying to start it up but otherwise runs fine. Took the car to a VW garage today and had it hooked up to the computer and only a software update and a temperature sender error were reported. Are the software updates worth bothering with, (VW say this will just turn the engine warning light off)? I will replace the temperature sender unit but will doing this or the s/w update resolve the intermittent misfire? I was going to replace the ignition coils as they have done nearly 40,000 miles but as these didn't show up on the computer I'm not sure if I need bother.
What to do….

your misfire may be related to the temp sensor fault anyway. Misfires are rarely attributable to software faults, almost always ignition parts or timing sensors. Should be no need to replace coils unless they are out of spec (easy to measure).

Thanks very much coffeeking, I'll replace the sensor and see how it goes.
Is it easy enough to do?

Should be a simple case of draining some fluid (doesnt need to be all fluid, usually a tap on the bottom of the radiator, save for re-use), unclipping the sensor connector and undoing it with an open-ender, then screwing the new one in, clip it up, re-fill and bleed coolant as required. Often the ECU will accept the new sensor after a few drive cycles when it realises it's working again, and turn the ECU light off by itself, but sometimes it may need resetting. You can buy the kit to do that for £25 on ebay should you need to (assuming you have a laptop with a spare usb port). Sensor is normally located near the head of the engine, at one end or the other, often on an obvious "arm" with several sensors in it and possibly the stat, I'm not sure on that car TBH – it's about a 1 or 2 spanner out of 5 in a haynes manual so should be no probs, though it may be awkward to get to.

If it's like my girlfriends 1.4 of the same era then the coils are prone to quitting. She had two go within two weeks..

However, when they died they stayed dead.

It is not unheard of for coils (especially on renaults for some reason) to break down intermittently, but usually it's a case of when it warms up they die, then come back alive when they cool down again. Intermittent misses might suggest a plug or HT lead fault (or distributor, but I suspect a car of that age does not have a dizzy).

Thanks again coffeeking. This sort of advice and help is invaluable so have you got a favourite charity I can donate to?

Coils, common as muck on Polo's

I had the same problem last year with my wifes polo. Temp Sender replacd, hunky dory 🙂

I serviced mine, replced the spark plugs, checkd the coil packs and the diagnostic puter (VW main dealer couldnt find a fault). Went to a back street garage, he said straight away temp sender and sorted the problem for £40 fitted

Thanks again coffeeking. This sort of advice and help is invaluable so have you got a favourite charity I can donate to?

It's no problem, all offered without expectation, hell if you were not too far away I'd come and help you do it, fixing cars is fun 🙂 I'm sure if you really feel you need to you'll know of a good charity to help, otherwise buy yourself or family something unexpected 🙂

had a polo for a while which we took back because of the engine management light problem and got a Focus instead. It's aparantley a common problem with the VW's of that era where one of the sensors constantly cokes up pretty badly……..and as they've said theres no real problem then prob nothing too much to worry about

All VW group cars of that age had an ignition coil fault, mine were replaced FOC.
My VRS light comes on and off intermittently and to quote the garage 'If you don't feel a loss in performance don't worry about it'

But in this case there's a coolant sensor fault, which is more than enough to cause a misfire (due to momentary false enrichment etc), so would keep that as your primary candidate and move on to ignition components once it's fixed. As a quick point, make sure you check the wiring to the sensor before changing the sensor – often wiring frays and obviously the computer will assume it's the sensor that died.

I'd say that a temp sender fault could cause all sorts of mayhem with the ECU not knowing what to do properly… Change it, worth the few quid it'll cost.

My Polo was having some issues starting during that massive cold snap we had, one replacement coil later it works 90% of the time all of the time!

Mt brother had one of those problems. He called it the £150 light. You can guess why. I think he got rid of the car as a result and swears never to buy another VW

I called it the £25 OBDII reader light and bypassed the dealers entirely 🙂 There's always someone willing to swear against a manufacturer, model and rip it to shreds based on their own experience with it. For example on here it seems to be fairly well accepted that peugeots/citroens are horrific, very unreliable and full of electrical faults. Well I've been responsible for the maintenance of at least 5 of varying age and type (owned by me and other family members and friends) and found them to be very very cheap to run and repair, and very reliable. All it takes is a little understanding of how cars work and a little common sense (and then finding someone who is reliable to repair them cheaply). At the end of the day cars are complex machines and have come a long way from the days of needing a full engine stripdown every 5000 miles (cars of my dads era), the odd niggling fault that is easily repaired (if you don't leave it to do damage) is not much to ask for hundreds of thousands of miles of cheap travel. Some companies do it better than others, but generally they cost more and are less efficient (heavier, longer lasting parts) but you pay more when they do have a fault – you make that choice when you buy.

Plus, to play the game well you gotta listen to the car. If it's making a funny noise, you have to notice, and get it checked out. Likewise if it's slightly down on power.

I hear people driving around with all kinds of nasty noises. You have to wonder who in the car's past skimped on maintenence. Plus, most mechanics won't bother to do a decent job on an old cheap car.