Running lumpy following service

Topic: Running lumpy following service (Read 1666 times) previous topic - next topic

Running lumpy following service

March 01, 2021, 02:48:48 PM

Car was running fine before, but have just done a full service to recommission after it’s sat for pretty much the year.

Fuel filter,
Oil and filter
Air filter
Changed dizzy cap, rotor and leads.
Didn’t do plugs they were out of stock.

Anyway now runs rough with a miss fire. Put the old cap, rotor and leads back on and still like it. Thought it might had been duff leads.

What am I missing?

Re: Running lumpy following service

Reply #1 – March 01, 2021, 02:52:26 PM

Just noticed.... on trying to start (it takes a little effort) I seem to have a power issue as the clock resets.

Re: Running lumpy following service

Reply #2 – March 01, 2021, 03:59:38 PM

Get a multimeter on the battery when it's running, your alternator may have had it and the battery is slowly discharging.

Re: Running lumpy following service

Reply #3 – March 01, 2021, 06:49:41 PM

Oh. I did clean the engine bay with paraffin in a spray gun running off the compressor. Wonder if some has got where it shouldn’t have.

Re: Running lumpy following service

Reply #4 – March 01, 2021, 11:35:00 PM

When changing the dizzy cap / rotor could you have rotated the dizzy at all?
Is the clamp tight?

Re: Running lumpy following service

Reply #5 – March 02, 2021, 10:44:38 AM

Quote from: sly_gti on March 01, 2021, 11:35:00 PM

When changing the dizzy cap / rotor could you have rotated the dizzy at all?
Is the clamp tight?

My history of Dizzy's is they're usually seized solid. But I suppose it's a possibility.

Re: Running lumpy following service

Reply #6 – March 16, 2021, 07:20:00 PM

Check voltage at battery and alteror as mentioned and check the battery earth cables too.

Re: Running lumpy following service

Reply #7 – March 17, 2021, 07:09:53 AM

14.4v at the battery when running. Didn’t check directly on the alternator though. Although battery now out and on a charger. Has been sat for most of a year now so might not be at its best.

Earth straps are good, battery straps were replaced with good strong mk3 ones.

It only happened since service and changing leads etc, perhaps I dislodged something, moved that dizzy unknowingly or something like that. Could any of the spade connections on the coil make a difference? There’s quite a bulk of wiring there, could have done something trying to access the king lead.

More investigation time required.

Re: Running lumpy following service

Reply #8 – March 17, 2021, 08:32:41 AM

It could well be the coil, the wiring is bloody awful in that area.
You could try jumping the car from another and see if it runs better with the other car on.
Also, when you say earth straps, I assume you've checked the connection on the gearbox is tight. Silly question I know, but I lost an ECU that way.

Let it run for a while, then pull the plugs, see if one of them is wet, that might show the same cylinder not firing and narrow things down.
If you find a wet one, that's the one that's not getting spark.

If all dry, you could also try starting the engine 4 times, each with one of the leads unplugged.
If you get a lead off and it still runs the same, yet the spark plug is dry, that'll point to a failing injector.

Re: Running lumpy following service

Reply #9 – March 17, 2021, 09:10:27 AM

I'll add something in, might be a wild idea but I had it once way back when I had a MK1 GTI, did a full service, plugs, rotor, Dizzy, filters etc the full works and started the car and it ran like crap, I went through everything swapping things back but the only thing I didn't change back was the fuel filter, as soon as I swapped that back to the old one it ran sweet as before, I still to this day had no idea why a fuel filter would be defective but seems it was.

Re: Running lumpy following service

Reply #10 – March 17, 2021, 09:26:32 AM

Quote from: t2000 on March 17, 2021, 09:10:27 AM

I'll add something in, might be a wild idea but I had it once way back when I had a MK1 GTI, did a full service, plugs, rotor, Dizzy, filters etc the full works and started the car and it ran like crap, I went through everything swapping things back but the only thing I didn't change back was the fuel filter, as soon as I swapped that back to the old one it ran sweet as before, I still to this day had no idea why a fuel filter would be defective but seems it was.

Interesting... I have swapped back everything bar the fuel filter. Worth a try when I get some time.

I'll do Monkey's tests above first, that seems easy enough but if nothing makes sense then I'll try the filter. Luckily I've not binned the old one yet.

Re: Running lumpy following service

Reply #11 – March 17, 2021, 12:04:15 PM

I was trying to order some service bits a few days ago (with Autodoc, to see how it goes!) but had to leave it until I got my head around the fuel filters.

The Bosch ones seem to come in different flavours for the PB engine, though I don't understand why nor which I'll need despite them all sharing the same cross references to the same VW OE part number.

Apart from different lengths and diameters (don't know if that matters too much yet) some are quoted as having 8mm in/outlets and others 9mm, I'm thinking that might be more of an issue?

Re: Running lumpy following service

Reply #12 – April 15, 2021, 03:08:52 PM

Have put the old fuel filter back on and no difference, so refitted the new one.
Will have to do the fault finding process above. Was hoping for a quick simple fix, would have been nice if it was just a faulty filter.

Dizzy is corroded solid in place, there's no fear I accidentally moved it.

I also did a double check I've fitted the filter the right way.
The arrow on the filter shows the flow of fuel from the tank to the engine.
I'm sure I copied what I removed but if someone can do me a sanity check that would be appreciated: ...

So the filter is inline after the pump, right ?
So the pipe comes out of the front of the pump and loops round into the filter,
So the arrow is actually pointing to the rear of the car, yes ?
Then the pipe comes out the back filter and loops round to follow on to the front of the car.

I'm kind of hoping I'm wrong and I've just been a twat and fitted the filter the wrong way. And as if by magic I'll be all good once I've corrected it. As typical the Haynes is no use and doesn't even picture a PB set up, either photo or diagram.

And the official fiche isn't that helpful either as it has the pump assembly technically facing the wrong way

Re: Running lumpy following service

Reply #13 – April 16, 2021, 02:18:14 PM

doh! I had leads 3 and 4 the wrong way round, even though I'd convinced myself they were correct. nothing like checking your own work.

Re: Running lumpy following service

Reply #14 – April 16, 2021, 02:43:25 PM

Haha! I did that once myself, thought I'd knackered the engine!