04 Highline 130 (AWX) 180k lumpy cold start

Hi all.. I don't post much (at all?) since I tend to find what I'm looking for on a search..
But I can't find a solution to this..

Slight rough startup (but immediate, no struggling to start at all)
Then, in the first ~5 minutes, between 1 & 3 times, it chugs like a mofo for a few seconds (and if I power through, there's loads of light coloured (grey I think) smoke)

Soon as the temp gauge starts moving it's fine.. no issues at all.

I've done a 1 litre diesel purge (chugged the whole litre at 2k+ revs, the dregs of the purge liquid were dirty) and also tried priming the fuel a few times before starting..
Air, fuel and cabin filter are less than 5k miles old. It could probably do with an oil/filter change..
It's had thermostat and coolant temp sensor (the one round the back) and new glow plugs.
Went through MOT with no issues.
No codes stored.
I've not deleted the egr yet.

It tends to get supermarket fuel but this problem didn't start until mid-December (after I'd had the car a couple of months)

Sorry to jump straight in asking for help..

93/93

Nobody...??

93/93

Mine starts a little rough, then smooths out pretty quick when it's cold. I keep mine in the garage though.

QuickTD said:

Pull the EGR vacuum hose off, plug the hose and run it. It will set a code for EGR insufficient flow but it shouldn't hurt performance. I have a suspicion about the EGR valve sticking open. Especially if this "chugging" happens after coming to a stop from cruising speed.

Try it for a few days. If it runs ok, the EGR valve may just need to be cleaned and freed up. EGR can be deleted easily in the mapping on these engines, if you so choose.

I am running AVF PD130 engine controls/EGR/anti-shudder on a north American BHW engine swapped into a B6 audi A4, so I'm familiar with the hardware.

Click to expand...

It only chugs a few times from cold, briefly just after starting and then a couple of times while driving - not usually when coming to a halt and definitely not at/from cruising speed..

EGR is getting deleted.. I'll start with just plugging the vac hose..

Thanks for the input chaps [emoji41]

93/93

QuickTD said:

Pull the EGR vacuum hose off, plug the hose and run it. It will set a code for EGR insufficient flow but it shouldn't hurt performance. I have a suspicion about the EGR valve sticking open. Especially if this "chugging" happens after coming to a stop from cruising speed.

Try it for a few days. If it runs ok, the EGR valve may just need to be cleaned and freed up. EGR can be deleted easily in the mapping on these engines, if you so choose.

I am running AVF PD130 engine controls/EGR/anti-shudder on a north American BHW engine swapped into a B6 audi A4, so I'm familiar with the hardware.

Click to expand...

Pulled the egr vac hose and plugged it, it ran worse.. borderline undriveable.
Also didn't show an eml.. But I didn't drive it far tbh.. a mile or 2..

*shrugs*

93/93

I'd suggest physically checking the EGR valve to see if it is stuck open.

Uberhare said:

I'd suggest physically checking the EGR valve to see if it is stuck open.

Click to expand...

It'll be in a permanently open position when deleted, no?

93/93

QuickTD said:

No. The EGR valve is spring loaded closed and is opened by vacuum. The ECU modulates the vacuum applied to the valve to vary the amount of exhaust gas admitted to the intake. The EGR valve is the UFO looking device protruding through the engine cover, located on the intake manifold, just to be clear.

Generally, the engine will run better with no EGR, but emissions of nitrogen oxides are increased.

A stuck open EGR valve will cause severe misfiring or stalling at idle and severe drivability problems, misfiring, smoking, low power, shuddering etc.

Click to expand...

I'll whip it off and clean it soon as it warms up a bit.. Then delete it.

There's no severity to the rough running though.
Few seconds on startup and a few seconds each time while cold..

It's only minorly inconvenient but obviously something's wrong that needs sorting.


93/93

Don't forget that egr valve puts heat into your cabin heater !
That is a real plus thing to have on a chilly day !

I have a similar issue that happens once in a while randomly when the outside temperature is under 40°F. It acts like it's loosing prime.

Glow plugs check out, I replaced the rubber fuel lines. I replaced Tank fuel pump in the past year. I also replaced the Tandem pump recently.
I am now thinking I have an injector seal issue that leaks when the temperature is low. How does one detect that on the VCDS?

QuickTD said:

You don't. Put a clear hose in place of the return line and look for bubbles. the seals tend to leak combustion gas into the fuel passages in the head. You will see bubbles/foam in the return line.

Click to expand...

I checked the lines for bubbles when I did the diesel purge.. Thankfully there were none.

The chugs wers a bit less this morning, not in frequency but in strength and duration.

I did read that this issue can be a problem with the warm up cycle but I can't find out much else about it..
Presumably that would involve a sensor and/or the ecu..

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Well.. This has got a little worse of late.
It's now 'chugging' 4 or 5 times and it's a bit worse than the previously quite gentle chug..

EGR deletion coming up I think.

Presumably it's the same (mechanical) process as the mk4 Golf..
Blanking plates to the exhaust and block the top vac hose..

After cleaning the thing.. and the inlet.

93/93