hello, I've been reading The back room for ages - and have been impressed with (nearly) all the threads and quality! Now I need help - so this is first post!
SWMBO has a S reg VW Polo 1.4CL - we've had it virtually from new. Its recently developed a sort of misfire - but only when it's warm, and only under harshish acceleration. It happens in all gears, and at all revs - its more annoying than anything else. Particurly noticeable when pulling away from junctions etc.
The last 3 fill ups have been with Optimax, and there has been a slight improvement - but why does this happen when its at normal temp. and not from cold? I've removed and cleaned air filter - and inspected electrics visually, all looks ok.
I'm reluctant to take to a garage to diagnose - as its difficult to explain - and ideally I'd like to be able to point them at the problem? Can anyone shed some light?
Tilda99
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Assuming an S plate did not have coil packs ( a common problem ) then you may just be chasing a failed HT lead, plug cap, plug or even distributor cap. As it appears to be heat sensitive i.e. OK when cold then may be the plugs, caps and leads are a good starting point. An independant tune up garage will find this quike quickly if you are not up to it. Can you give us more information i.e. is the mis fire regular i.e. on one cylinder or is it more random, like any cylinder. Regards Peter
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it feels like it's only on 1 cylinder - maybe hesitation is the best way to describe it - ie it accelerates but it's very jerky.
I wondered about electrics - years ago (on a different car), I had a similar problem, I think, and I'm pretty sure the cure was a new condensor (about 20p then!). My knowledge hasn't really moved forward much since then - do modern electrics have condensors anymore?
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No condensors but when was the car serviced last, new plugs etc. Regards Peter
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Thanks for the comments - last serviced in Aug 05, 4000 miles ago. Plugs and leads not replaced - so I'll start by doing that. But why the misfire only when hot - everything is fine for the 5 mins or so when starting from cold?
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The richer fuel mixture when cold may be hiding the mis-fire a good diagnostic tune up place would be able to find it when cold as well but if it shows when hot then assuming everthing is OK internally i.e. valves and valve clearances then It could just be a faulty or contaminated plug. I assume this is a single point fuel injection engine is it. ? Regards Peter
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It could be the (ECU) coolant temperature sensor.
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When was the last time it had a new fuel filter?
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First post too....my P reg 1.4CL was suffering what sound like the same symptoms- running fine from cold and misfiring increasingly as it warmed up. Changed the plugs, checked the HT leads- all to no avail. It turned out to be a failed water pump that was causing the engine to overheat. The temperature gauge didn't move above normal as there was no water circulating, right up until it boiled over on the M5! Apparently the water pumps have plastic impellers so you can't hear when they have failed - so might be worth checking. Ran perfectly again once a new water pump had been fitted.
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Thanks for the advice - here's an update. (Have been out of the counntry, hence the delay!)
Changed plugs yesterday, and also cleaned out a load of whiteish sludge from a small breather tube that feeds into the air filter housing (from the crankcase???).
Anyway, runs like a dream now, so either it was plugs or the sludge! Can now take the unnecessary HT leads I bought back to Halfords for a refund! Thanks T99
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