Hi guys, first post here so be kind!

I have just bought (for not a lot to be fair) a 1.0L, 98R Polo as a bit of a runabout (well to leave at a railway station all day). When I got the car it was fine, however since giving it a bit of welly (only 5k) the other day it seems to run very rough - almost like a misfire but not as bad. When at idle it is fine upto 2k then sounds slightly offbeat and rough onwards although does get better over 3k.

I've replaced the leads and it's no better, the plugs look okay, but not great (will replace them at the weekend) - doesn't overheat although I fear the headgasket is on it's way out as I cleaned some Mayo off the filler cap the other day - however there is no oil in the water and the dipstick looks fine and although I've topped the coolant up it was only a little to get it accurate to the line.

To you technical guys out there, could a potential headgasket leak be causing the uneven running? I drove the car today and after a short while it felt okay for a bit then reverted back to it's old ways making me think that it's not - do you think that this could be a dodgy spark plug ?

Let me have your thoughts as it really gets on my nerves driving a 'dub that's not right - even though it is a 1.0!

Cheers!

Hi,

Sounds like your problem shares some characteristics with mine! Although mine now only runs on 3 cyls when I got it it ran on 4 but quite rough. I don't have mayo in the filler (yours may just be because of short runs in this weather?) but my next step is compression testing to work out what's happening as I have perfect spark. Wierd eh?

don't worry about a little bit of mayo on the filler, it's only condensation.

could be a whole number of things tbh, ignition coil, map sensor, dizzy cap etc etc, have you done a diagnostics check? it's more likely to be ignition system related

yep very weird! ... It still drives okay and I have not driven the 1.0 enough to notice any lack of power - in fact if you give it some boot, it goes okay ... well in it's own world anyway as have Golf GT TDI 140 also.

Can't help thinking it may be a rogue plug but ... it's never that simple! .... once warmed up it does have a very low idle (600rpm) ... could this be linked to the coolant temp sensor? ....

I have read the forums and think I might try to disconnect the Lambda sensor and see if that cures it? ... all trial and error!

Might have a play at the weekend if the snow goes!

ah low idle gremlins again eh?? have you run the battery down or disconnected it recently?? do you have access to vag-com?? try reseting the throttle body alignment

a rogue plug generally will cause a miss throughout the entire rev range, the coolant sensor does play a part in idle speed and base ignition timing but the adjustment range is fairly limited maybe +-150 revs at most, normally if the coolant temp signal to the ecu is way off it just dismisses it as 'duff data' and substitutes it for a reference value instead

disconnecting the lambda probe will just make it run rich, and possibly not run as smooth as normal

don't worry about a little bit of mayo on the filler, it's only condensation.

could be a whole number of things tbh, ignition coil, map sensor, dizzy cap etc etc, have you done a diagnostics check? it's more likely to be ignition system related

Will have to do one of those .... will check the various sensors first. How do you check the coil ... it's a really weird little unit, not individual coil packs like on the newer stuff (that all go wrong!)

How do you check the coil ... it's a really weird little unit, not individual coil packs like on the newer stuff

best thing is to just swap it out for another known good one tbh to rule it out unless you have some sort of test equipment... it has the amplifier and transformer contained in a sealed unit

pin 1 : ground

pin 2 : LT signal from ecu

pin 3 : +12v from fuel pump relay

....what I don't understand is that on idle and upto 2k revs it's sweet as hell - it's almost like the timing is out when it goes above 2k .... although it still revs and goes okay.

Think it would be prudent to get the thing on VAG-Com at some point! PS. (and I sound stupid here as have had loads of veedubs) ...why is there no engine management light on? .... or is it the engine is quite primitive with regards self-diagnostics etc?

try giving the throttle body a good clean and disconnect the battery for about an hour.

that normally sorts mine out. :-)

try giving the throttle body a good clean and disconnect the battery for about an hour.

that normally sorts mine out. :-)

Yeah and maybe put some Redex or something similar in your fuel tank to flush out any crap from your injector(s). Is it an SPI? Are you sure it's fuelling ok?