Hunting down FR 150 TDI surge issues

[iammooks]

Bit of a development...

Took the car out with the EGR vacuum hose clamped, and the hesitation is gone. Parked up after a while and took the clamp off and the hesitation came back.

Feels like I'm making progress.

From what I'm reading, this doesn't mean the EGR is bad, as it could be pretty much anything connected to the EGR system, but it sounds like a start. I'm not interested in deleting the EGR so will probably fit the replacement valve I've got and then start working my way through.

Unless anybody has any suggestions...?

 

[Rich.T]

Good to know you're finally on the right track now

 

[iammooks]

Good to know you're finally on the right track now

It was nice to go for a drive and not have that issue for a change. The car is holding boost well and the brakes felt more firm. It's actually a bit weird expecting something to happen and it not happening.

Now it's just a matter of working out where exactly the problem is - you'd think it would just be a matter of changing the EGR valve, but a lot of people are saying that didn't solve it, so it could be the N75.

Back to the research...


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[iammooks]

It was nice to go for a drive and not have that issue for a change. The car is holding boost well and the brakes felt more firm. It's actually a bit weird expecting something to happen and it not happening.

Now it's just a matter of working out where exactly the problem is - you'd think it would just be a matter of changing the EGR valve, but a lot of people are saying that didn't solve it, so it could be the N75.

Back to the research...


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Well, research is suggesting that the EGR is controlled with the N18 and not N75...

Being this close to sorting it, it's tempting to just buy all the things I might need, but I'll probably start with whatever is cheaper...


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[Rich.T]

Well, research is suggesting that the EGR is controlled with the N18 and not N75...

Being this close to sorting it, it's tempting to just buy all the things I might need, but I'll probably start with whatever is cheaper...


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And easier to fit

 

[iammooks]

And easier to fit

Compared to changing the injector loom or putting in a new camshaft, it's a walk in the park.

Ordered a new N18 from Darkside and will fit it next week.

It sounds like most of my engine problems of the past few years could be down to this, since if it fails or is failing, it affects emissions - a lot.

Just looking at all the things it could be is exhausting though - from boost leaks to vacuum leaks to fuel filters to injectors to injector looms to camshafts to vacuum controllers to the EGR valve... And that's not all...

If this works, I'm going to be made up.


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[iammooks]

New N18 installed yesterday and drove to Euros today to pick up an oil filter.

Car still hesitates in low gears and is now noticeable downhill in sixth gear.

It does feel different, but there's clearly still an issue.

I'm going to take the EGR out over the weekend and give it a clean, as well as to make sure the plunger can move freely. I'll try some lube on that as well, in case the grime over the years is stopping it from actuating fully. If that doesn't work, I'll put the brand new EGR in and see what difference that makes.

I feel like I'm in the right area, given that the hesitation stops when I clamp the EGR vacuum line, but it seems there are still a couple of things it could be.

Not quite ready to throw the car in the bin just yet, but I'm getting there...

 

[iammooks]

Just taken the EGR valve out of the car...

While it looks like there's only a few millimetres of movement in the plunger, if I put pressure on it with a screwdriver it moves all the way and if I put my finger over where the vacuum line goes in, it seems to hold vacuum and the same goes for the anti-shudder valve too.

There doesn't seem to be any stiction in the vacuum diaphragm either - it moves pretty smoothly.

I did have a look at the EGR cooler as well and that seems pretty sooty...

Is it possible this is blocked, or maybe the lower EGR pipe too?


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[BigJase88]

The cooler might be but that EGR valve looks very clean

 

[Rich.T]

The plunger doesnt seem to move very much though.

 

[iammooks]

I cleaned the EGR valve itself in early 2020 and haven't really done many miles since, so that's probably the reason. It was pretty awful when I took it off then though - I should have weighed the gunk because there was a lot.

The trouble with the cooler is that it's still on the car and so I can't work out if it's blocked or it's just because you can't see daylight on the other side.

I have a feeling the cooler and the lower EGR pipe might need a clean. It can't do it any harm but I'm still a bit anxious about trying to get at those allen bolts.

The car is parked on a hill at the moment so there's no chance of jacking it up. I have a feeling the lower EGR pipe is easier to undo from under the car, so I might try and do that when I change the oil next week.


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[iammooks]

EGR valve went back in the car yesterday. It was supposed to go in on Saturday but I dropped one of the metal gaskets when I was trying to put it back in. My method for getting all of the bolts tight is putting the EGR valve in first and bolting that to the intake manifold, before putting the EGR pipe underneath and inserting the gaskets enough to get the bolt through the hole to keep it in place and then gently finger tightening the allen bolts before doing them up with an allen key.

I couldn't find the gasket so used a new one I had, along with a new paper gasket. I remember having been told to use a paper gasket on the EGR pipe to EGR cooler and a metal one where it connects to the EGR valve, but this isn't right as far as I've been able to find, and the paper gasket had stuck to both pipes and fell apart when I prised it off.

Before I put the EGR back in the car though, I wanted to test it alongside the new one to see whether it behaves in the same way. Other than the anti-shudder valve making a clicking sound on the new one, the actual EGR diaphragm seems to operate just as smoothly and when I did a poor-man's vacuum test by putting a vacuum hose on, pushing the plunger and clamping the hose, both valves behaved the same way. It seems like my old EGR valve is definitely still working.

So, how did it drive...?

I didn't have a chance to drive the car until this morning so did a good 15-20 minute drive where I was doing a steady 30mph with the engine cold, had a chance to open it up once the engine was warmed up, then back to lower speeds before getting back home. No shudder when the engine was cold, definitely none when the engine was being pushed (but then it never has) and then when I got back into town, there was nothing really noticeable. I've always had a bit of a shudder when I've revved in a lower gear, lifted off, and then come back on the gas, but I think that's just my driving style annoying the ECU. Today I didn't have the feeling that the engine was missing a beat just driving at 30mph with the revs at 2,000-2,500rpm, which is where it's been happening the most.

The whooshing sound under boost in low gears is much quieter now too. You can still hear the turbo spool up, but to me that's normal.

Is it possible I fixed the problem by cleaning the EGR valve and then adding new gaskets? Maybe. I've read so many posts on so many forums where they say they changed the EGR valve and the problem went away for a few weeks before coming back, so time will probably tell.

I have come across more posts lately that say that there's a reducing gasket available - part number 028131547B - that's from a mk3 Ibiza from what I can tell, and it's cured a lot of people's engine hesitation by reducing the exhaust gas flow. If the problem comes back, I'll give the dealer a call to see if they can get hold of some.

In the meantime, I might be giving the car a good run in a week's time, which will be a good chance to test if it's worked, and I'll put some fresh oil in the car too if it keeps up. We'll see what happens...

 

[smutts]

Glad to hear you're making progress. EGR horrors brings back unpleasant memories of a Lexus 220D I battled with a few years ago.
It was basically caused by engine sensors handing bollocks to the engine management computer & the computer believing it.
No error codes, but more smoke than a thousand teenagers on RD 250's.

One way they control the EGR valve especially the VW steampunk EGR valve, the computer knows how much the engine will breather per turn (swept volume times the pressure from the intake pressure sensor, it knows how much poo (EGR) that's required, so it turns on the vacuum solenoid to open the EGR valve until the airflow measured drops to the desired point. This assumes good info from the flow sensor & the pressure sensor.

EGR flow = Total Swept flow (assumed) - Measured flow

It makes sense to me, but I am on my third beer.

Anyway, could a duff, or wrong airflow sensor cause the computer to try stuffing the engine with too much of it's own exhaust crap?

 

[iammooks]

Glad to hear you're making progress. EGR horrors brings back unpleasant memories of a Lexus 220D I battled with a few years ago.
It was basically caused by engine sensors handing bollocks to the engine management computer & the computer believing it.
No error codes, but more smoke than a thousand teenagers on RD 250's.

One way they control the EGR valve especially the VW steampunk EGR valve, the computer knows how much the engine will breather per turn (swept volume times the pressure from the intake pressure sensor, it knows how much poo (EGR) that's required, so it turns on the vacuum solenoid to open the EGR valve until the airflow measured drops to the desired point. This assumes good info from the flow sensor & the pressure sensor.

EGR flow = Total Swept flow (assumed) - Measured flow

It makes sense to me, but I am on my third beer.

Anyway, could a duff, or wrong airflow sensor cause the computer to try stuffing the engine with too much of it's own exhaust crap?

Yep - it's why it's such a pain to diagnose what the problem actually is. It's easy to think that given the problem went away when I clamped the EGR vacuum hose, then it must be a problem with the EGR valve itself, but if the MAF isn't reading properly, or the MAP isn't getting the pressure it's expecting, it's messing with all of the calculations, from the amount the turbo spools to the amount of fuel going through the injectors.

I'm going to give it a couple of longer runs when I get the chance, some motorway driving and some town driving as well, just to see what happens over a couple of weeks of regular use. For the time being though, I'm feeling positive, which I haven't felt in a while now.

 

[smutts]

Just another thing to look at.

VW's temperature sender has two thermistors, one that runs the dash temperature gauge, the other that goes to the engine management.
My engine was a bit "off" for a while until I found the hot engine temp reported by VCDS as minus 55C.
No polar bears on Dartmoor, The dash guage was working perfectly.
New sender sorted it.

Is EGR flow increased with a "cold" engine to warm it up faster?

 

[iammooks]

Just another thing to look at.

VW's temperature sender has two thermistors, one that runs the dash temperature gauge, the other that goes to the engine management.
My engine was a bit "off" for a while until I found the hot engine temp reported by VCDS as minus 55C.
No polar bears on Dartmoor, The dash guage was working perfectly.
New sender sorted it.

Is EGR flow increased with a "cold" engine to warm it up faster?

Interesting you say that - yesterday I was waiting at some traffic lights, engine still cold, when the revs all of a sudden went up from about 1,900rpm to 2,100rpm and back down again. It did that twice but didn't happen after that.

I probably wouldn't have noticed if I wasn't so tuned in to what the engine is doing these days, but that's not normal and hasn't happened before. I'll have to look into the sensors too.

As far as I know, the EGR is closed until the engine is warm and then it opens up at higher speeds. When you're idling in traffic, it closes, and so I'm wondering if my stutter isn't the EGR closing when I'm letting off the gas.

On yesterday's drive there was some hesitation, but it wasn't as jarring - it's definitely smoother than it was before. I put some Miller's in the day before too just in case.

The car is old enough to have things go wrong, which is fine - just as long as it's not ridiculously expensive things going wrong.


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[MoToJoJo]

EGR opens at low engine speed, especially when idling. It isn't used for engine warming as far as I know, think that's just fast idle as on petrols (dervs don't *need* to but it helps)

 

[iammooks]

It's baaaaaack...

Did 100 miles on a-roads and motorways today and the surge was definitely there. Less aggressive than before, but definitely there and definitely noticeable.

Kept a close eye on the rev counter and the boost gauge when it was happening and neither was moving when it was surging.

MPG is still down by a lot too - on the run I did today I should be getting 54mpg bit it was barely at 44. I've noticed the exhaust pipe is coated in soot too.

I thought maybe the lower EGR pipe was blocked, but the upper one I cleaned a few months back and it's got a lining of soot, so the exhaust gas is definitely getting through.

Lots of soot at the exhaust is making me think it's either overfuelling or it's unburnt fuel, which in turn makes me think it's probably the intake manifold - fuel is going in but it's not being burnt in one of the ports, which explains why it's down on power and up on fuel consumption.

I'm going to have to take it out, aren't I?


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[MoToJoJo]

Find someone with VCDS and get them to log your cams torsion value (cam timing). It's unlikely the problem (unless you've had the cam belt changed) but it's an easy test/fix. Hell, maybe be worth getting someone to log the car on a run to see what the engine is doing when it surges.

If it's not that then I think overfueling would mean not enough air getting in. Maybe worth smoke testing to check for leaks.

If it's none of that then yeah, looks like time to attack the inlet manifold

 

[iammooks]

It looks like the problem is solved.

Did an oil change today and decided to check the boost pipes while I was under the car. Found that the intercooler boost pipe on the MAP side was off.

I hadn't checked it because it was replaced by a garage last August and I stupidly assumed that it was going to be fine. When I saw the pipe like that, I thought it would just be a matter of taking out the horseshoe clip and re-seating it.

Nope.

The garage had obviously snapped it when they put the new boost pipe in, but didn't replace it and didn't tell me. They probably thought it would be OK, but it popped off pretty much when I drove it away. It wasn't quite enough to cause huge problems with the engine, but it was enough for there to be a noticeable whooshing noise and the stutter. I had taken it back to them because the surging only really started after they fitted the boost pipe, as well as the noise of the boost leak, but they were suggesting that the fix they'd done had just made other leaks more obvious and wanted to change the boost pipe on the other side of the intercooler.

I've ordered a replacement clip for it, but while I wait for it to arrive, I got a 60-80mm jubilee clamp on it from Halfords. Took it out for a drive and...

No stutter.

Drove the 100 miles back to Brighton and no issues. No smoke out the back when I accelerate at low load (in fifth or sixth) and I'm back to 54mpg too. The power delivery is much better as well. Beforehand it felt like I was hitting the rev limiter, but now it's a much more progressive feeling. There's no hiss on acceleration either.

In the end I'm annoyed - annoyed at the garage for doing such a bad job of it but also annoyed at myself for not finding it sooner. It should have been the first thing I checked, but because it had been changed by a garage I thought it should have been done properly. Since then I've bought a new EGR valve, changed all the vacuum lines and fitted a new N18 as well. Work I didn't need to do and money I didn't need to spend.

In all, I've spent about £150 on parts, filters and things like injector cleaners when what fixed it cost less than a fiver. Worst part is that I took the car to the garage for diagnostics, not a boost pipe, but when they couldn't get their scanner to work on the car, they changed the boost pipe instead. I could have done that with my eyes closed - and I wouldn't have used a broken clip either.

That'll teach me.


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