Spluttering - UPDATE 04/07

[Alex]

Not totally sure what's at fault here, but I seem to have an intermittent missfire under load. The car bogs down and splutters.

But it is intermittent.

The first time it happened was back in February, I hadn't used the car much due to the snow. It was down to the dregs in the tank, so I the first place I drove it was down to the BP garage down the road and it was spluttering then.

Then I had a poor month in April, decided to leave the car in the garage for a few weeks as it's a bit thirsty. Got it out at the beginning of May, again with dregs in the tank, drove it to the garage and filled up. No drama. Drove it to work the next day and for the first two or three miles it was spluttering. Then it seemed to clear and it was fine (actually, it was bloody brilliant) for a month.

Being a bit of a nob, and very busy at work, I ran it down to fumes last Friday. It was fine, but there's no Shell garage near me so I wanted to fill up after work (there's one near the office). As I drove away from the office it was spluttering a bit, then on the way back to mine it was doing it really badly. Really smooth while cruising, but bogging down with no power when on boost. Which to my mind suggests a fueling issue?

Well to add complication to it, someone who moved my car at Mod Nats the weekend before had said my clutch needed adjusting so I thought I'd have a fiddle on Friday before driving to get fuel.

On Sunday I changed the fuel filter, assuming it was clogged.

Just been out for a spin and again, first few minutes it was spluttering quite badly. Idling beautifully though! So I stopped, wound the clutch back to where it was, roughly, and it seemed to be better afterwards. Actually, it seems fine.

So I'm wondering, is this an issue with fueling? And could it be as simple as having a load of shit at the bottom of my tank?

Or is it something more sinister, like a faulty component. I know it's not the lambda, as it didn't have one between October and mid April and the first couple of spluttering moments it was running without a lambda. Now it's got one, and it's doing the same.

Or could having a clutch not biting properly cause it to splutter a bit under load?

[Alex]

Hmm, another possibility, could it be an ignition problem?

There's a burble from the exhaust when it bogs down. Maybe it's unburnt fuel?

[Etches]

Mine does the exact same dude proper bogs down

[PeteG40]

sounds like yr problem alex is shit fuel either old or bottom of the tank

top it up, shake it about - hopefully it'll go away

[Alex]

I'll limp it to work tomorrow then, leave early just in case, put a bit more in and see what the score is.

The old girl's been running really well recently (as in, for the entire last year) so I'm gonna be gutted if she starts acting up.

Shit scared of piston meltage, not a club I can afford to join!

[Varley]

I'd vote for ignition issue, despite the running on fumes references. Have a look/replace plugs, rotor arm and dizzy cap?

Solved my 'spluttering' recently...

Clutch bit a red herring I reckon.

[g40willa]

How are your earths? make sure the one from the coil to the gbox is strong.
I've had similar symptoms which I fixed by making 3 earth points, the one mentioned above, then I made one from the earth point on the inlet manif to the bulkhead, and one from the cylinder head to the o/s suspension turret.

Worth a go!

[Alex]

All my earth straps are new, and greased to avoid rust setting in.

Rotor arm and dizzy cap are fairly new too - Geniune VAG and only a year or so old.

Where's the cheapest place to get W5DPOs?

[PeteG40]

GSF probably, though people have generally used ngk and they are half the price! £20 a set delivered on ebay.

[Alex]

It's running NGKs at the moment

[Alex]

Bit of an update today, drove the car to DC10 and back. Or rather, limped.

I wanted to see if it'd get better with use, and tbh while it's been worse it's really not happy.

It's shuddering on part throttle and bogging down intermittently on full throttle (or under heavy load), makes a bub-bub-bub noise from the exhaust when it does so.

Thinking it may not be the fuel (I topped up with half a tank of BP Ultimate on the way back, which made no difference) but not sure what it could be.

I bought Quantum leads at BVF last year so I'll replace those tomorrow, see what it does. I'll check the spark plugs, dizzy cap and rotor arm too.

But if it's not the fuel and not the ignition system, what could this be?

[Nick_S]

Swap the fuel pump relay and see if it goes better. This relay is the same on all mk3's, easy enough trial

[Alex]

Hmm yeah scrap yard trip tomorrow then

[Justin14100]

Bit of an update today, drove the car to DC10 and back. Or rather, limped.

I wanted to see if it'd get better with use, and tbh while it's been worse it's really not happy.

It's shuddering on part throttle and bogging down intermittently on full throttle (or under heavy load), makes a bub-bub-bub noise from the exhaust when it does so.

Thinking it may not be the fuel (I topped up with half a tank of BP Ultimate on the way back, which made no difference) but not sure what it could be.

I bought Quantum leads at BVF last year so I'll replace those tomorrow, see what it does. I'll check the spark plugs, dizzy cap and rotor arm too.

But if it's not the fuel and not the ignition system, what could this be?

Try unplugging the lambda while its idleing? mine was a bit like that when it happened on mine. 30 second job would find a solution or rule it out!

[Alex]

Tried that earlier