Engine shuddering but not misfiring, what's going on?

[William444555]

Started my VW Polo MK4 (yes 2001 make 17 year old car) and it seemed fine, air temp today has been around 5°C (41°F), initially I waited 30 seconds so the windscreen de misted and drive off. The engine was stuttering going up any incline or when I put my foot down with a noticeable reduce in power, so I thought my 95k mile clutch finally was giving way as the car was shuddering a lot. Then I stopped at a red light and the idle kept dropping, so I plugged in my OBD2 reader, no fault codes at all.
I have had a missfire before when I spark plug was faulty and it came up on the dash and OBD2.

Does anyone have any ideas on what's up or how much it may cost to fix, if I can fix it myself, I'm pretty handy if it saves me a bit

[Krikkit]

Could be a few things, does it go away when hot?

No offense, but I'd get someone to look at it with a bit more of an idea, will be a lot less faffing around!

[steveo3002]

had very similar on our old focus , no codes shown , was a stumble at low revs worse on a hill /load ...was plug leads

[William444555]

Yep, if it was something simple I'd do it but it's more than likely going to the garage. And it doesn't go away when the engine is at operating temperature, and only got my sparkplugs changed and everything serviced 3000 miles ago

[Tony1963]

It’s an old car, the electrics are getting on, and it could be any one of a few dozen causes.

Yep, find a trusted garage and keep your fingers crossed.

[Penelope Stopit]

Wait until the end of daylight, open the bonnet, start engine and look for the coil and spark plugs high voltage tracking to earth somewhere

[E-bmw]

As above, a good way to see "leaking" sparks, it sounds like although you are getting a spark, it probably isn't a full one, probably just enough to stop reports of "misfire" by the ECU.

[steveo3002]

can mist water over the engine in the dark to look for sparks...although mind you dont get a shock off it

if the plugs were changed they might have damaged a tired ignition lead , guessing my issue had shown up as its almost constantly damp out now ?

set of quality leads shouldnt be more than £25 or so , can fit them yourself and isnt a bad idea on a older car anyway

[GreenV8S]

William444555 said:

I stopped at a red light and the idle kept dropping

A weak spark will tend to misfire under load, which can be awkward to trace. However, if you can get the problem to occur at idle then you can find whether it is associated with a specific cylinder by disconnecting the injectors one by one. If the engine stumbles badly, the cylinder was probably running OK; if it doesn't make much difference, the cylinder wasn't pulling its weight.

If you can trace it to a cylinder then you can swap components with another known good cylinder and see whether the problem moves with the component.

[William444555]

Thanks everyone for giving me an idea of what my issue may be. I drove back home and there was no noticeable issue. However I will take it to a trusted garage when I have the chance to see what's up, all I need is another 8 months out of the car until I'm (hopefully) at uni.
On a separate not when I got the spark plugs changed I also got the leads changed. It just seems a very unusual problem I can't find any information on the internet at all.
The abs warning light also sometimes decided to come and go randomly so I'd assume all the issues are related to a faulty ECU or something to do with the electronics

[Huskyman]

Have you checked your battery? It sounds odd but when a car starts throwing some odd faults on other electrical systems it can be the battery. Check the engine earth strap as well

[William444555]

Battery got replaced along with spark plugs, leads and suspension (and a few other bits and pieces) but I'll give the earth lead a look at, thanks