S40 losing power/limp mode

[Cakey_]

Hi guys wondering if anyone has any suggestions with my s40.

I recently bought it from a dealer as a px to clear, I paid peanuts for it so don't want to pester them too much.

Car is a 2005/6 2.0D psa engine I believe.
So when I bought it they said it had a problem with the throttle but would be fixed before I collected.

I picked the car up and it has a very occasional blip where it will shudder violently then go into limp mode.
There is no warnings on the dash whatsoever.

I took the car back to the garage who scanned it and said it had 2 codes stored, one for a glow plug relay and one for soot levels in the DPF.
They said that it's got a glow plug out which will prevent the DPF from regenerating.
They then put 4 new glow plugs in the car and said to take it for a decent run.

Well before I got as far as a decent run, literally going down the slip way it pinged into limp mode again, regardless I ran it 20-30minutes down the motorway. Pulled off switched it off and back on again which took it out of limp mode and went back down the motorway.

I'm convinced it's now had a decent run so if the problem was DPF it would've cleared, it also never showed me a dpf light so not convinced that's the problem.

Anyway it's still going into limp mode randomly, I can't find any circumstance that cause it to happen it just seems random to me.

Does anyone have any suggestions of what the problem could be?

[Cakey_]

No messages whatsoever on the dash nor any warning lights.
It just lacks boost, and will not accelerate past 2500-2800 rpm.

If you short shift around 2000rpm it's possible to drive, just incredibly slowly and there's violent engine breaking if you lift off the throttle.

9 times out of 10 a switch off and on again will solve it and the problem doesn't always come straight back.

It's very irregular so hard to pinpoint exactly what's causing it.
Although if accelerating hard upto about 4000rpm it happens more regular but also sometimes when driving mrs daisy about town.

[Cakey_]

Thanks for the replies, I believe mine does have a wet DPF so will check the fluid levels when I get the chance.

I gave the garage £900 for my car with a full service history and a cambelt 2 years ago.
It looks tatty buy I quite like that as it means I'm not to precious about where I park it!
I think the previous owner used the rear bumper as a parking sensor and stopped when they heard a crunch 😅

I expected to hate it but there's something I quite like about it except for the fact it runs like a dog.
Full cream leather interior with heated seats is actually a pretty nice place to be for the money.

Mine also shudders sometimes violently at a steady throttle and when sat in neutral on tick over. Sometimes so much my 5yo daughter starts complaining it makes her feel sick!
I'll look into replacing the MAF and see of that helps.

I'm trying not to throw loads of money at it as cheap cars can quite quickly stop bring cheap when you replace every little thing.

I do plan to pull the CEM and give that a clean up and see if that helps as there's a lot online of those getting corrosion amd causing problems and a can of contact cleaner is pretty cheap if it helps.

[Cakey_]

I've had the garage scan the codes and only thing that came up was dpf and glow plugs.
They've replaced the glow plugs and it made no difference whatsoever.

I've done abit of reading online and it's pointing at generic MAF problems for some of the issues, it starts and quite often will fire then stall if I don't give it a blip of the throttle, it judder a lot at idle, and steady revs can be quite lurchy too.
I'll can a can of cleaner and give it a spray and see if it helps.

I stuck some red ex in it yesterday and when it's running well it seems better, the power snd torque is there most of the time, I didn't realise until then how down on power it was, but then a clogged dpf won't help that either.
Limp mode is still intermittent with no noticeable cause.

It's annoying as when it's driving how it should it's actually a nice drive, the engine although getting a bad time online drives nicely with a decent lump of torque and generally smooth.

Im kind of stumped what to do next really, as if there's no codes being stored and no warning lights either it's a bit of a lucky dip to what the problem is.
I'm also conscious that i didn't pay an awful lot for it and it's tatty so don't want to spend hundreds throwing parts at it.

[Cakey_]

Thanks for the link, thats very intresting.
Just fell down the rabbit hole of old forum posts on Google but there was a chap somewhere suggesting he'd found a split in the rubber pipes running from the DPF to that pressure sensor.
It gives me another option of things to look at over the weekend.
I'm really hoping i can get it sorted as i quite like the car for what it is and would happily drive it for a couple of years if I can get the old girl working properly.

[Cakey_]

So I had an hour spare late afternoon so had a quick look over the car.

The pipes to the DPF pressure senor looked OK, I tried to pop them off but they were stuck fast and it was quite fiddly with big hands next to the engine block so thought best to leave that for another day incase I broke something in a rush as darkness was closing in.

I did notice some air bubbles in the clear fuel line and a few slightly bigger ones getting pulled through when I started it up so wonder how normal that is and if that could be part of my problem.

I also had a brief look over the boost pipes for obvious splits and noticed on the pipe that goes from the intercooler to the inlet manifold a lot of wet black oil coming from some sort of actuator or valve that fits between the pipe and the manifold.
If anyone knows what the part is it might help me figure out wether that's a problem or not.
There wasn't any electrical plugs on it but was a small vacuum hose attached but couldn't see where that was going to.