T4 Boost cut off!
 

Evening all,

I've had this problem for a while now on/off (yes, har har, my car is poo)

It will randomly go into some sort of 'limp' mode and limit boost to 0.5 bar, only I've got no idea what causes it or how to stop it from happening.

It does it every few weeks but it did it once yesterday and twice this morning. A quick restart of the car and it's all fine and reaches full 1.35/1.4bar boost again. There are no boost spikes, it peaks and holds exactly as it should when it's working, temps are fine..

Things that have recently been replaced (turbo wise):

- Replaced my TCV - Problem occurred on the old TCV too.
- Checked all boost pipes
- Turbo
- Replaced spark plugs (gen Volvo)
- Replaced both coil packs for new parts
- Replaced HT leads
- Full service inc filters - Air, oil and fuel
- Had codes read from Volvo every time it happens - Nothing shows up other than 'faulty xenon self leveling unit' which I'm aware of
- No engine management lights come up

So it can be fine for days/weeks boosting well, then randomly limit to 0.5 bar - restart the car and it's fine again, without logging any codes.

Any ideas? :thumbs_up:

Thanks

Hi Alex,

It may be intermittently overshooting on boost. Once the MAF senses airflow over a certain limit the ECU will pull back and go into limp mode. My car has done the same. Could be actuator adjustment, exhaust leak, Vac/boost leak and probably several other sensor related issues.

I still need to hunt down a vac leak on mine somewhere causing a rough idle sporadically. Although not putting it into limp mode, I get the odd lambda code. But..... Yesterday I found I had a very slight exhaust manifold leak so sorting that first to see if it cures it (fingers crossed). I hate Vac leaks sometimes they are a complete pain to find. I simply can't be bothered ATM!!

Hi Mitch,

The actuator is setup properly, was calibrated by Volvo a few months back when I had the new turbo put on, obviously waste gate is new so I doubt that is playing up. I had my exhaust manifold off last year, refurbed properly and put back on, no leaks there - Pipes I've checked and there are no issues there either.

MAF is an interesting idea. That's one of the few things left of the car since I bought it that I've not replaced. I also have a K&N panel filter so I'm wondering if maybe some of the oil has seeped through onto the MAF - I would have thought I would have had more issues if that was the case though.

Maybe I should look into that next.

I've spoken with Ashok and he agrees it's an odd one, I've tried all the things he's suggested so far to no avail. Volvo are just as stuck and they know the car pretty well lol.

MAF are interesting things though Alex - Mine has a fault within the wiring yet the car runs perfectly!

Coolant temp sensor fault?
My t4 limits boost pressure to 6-7psi when the coolant temp is lower than it should be.

Replaced thermostat last week, wasn't getting hot before but was still hitting full boost so don't think that's the problem.

Thanks though :)

Yes but are you sure the ecu is not losing the coolant sensor for a short amount of time, just enough to trip it into limp mode but not record a fault.

Hmm, interesting. I'll have a look into that. Thanks

Apparently if it's the coolant sensor it'll throw up a code...

Given I've never had any codes I doubt that's the issue.

Thanks

Sounds very much like the problem my brother had with his Audi 1.9Tdi. That would go into limp mode for no reason. A VAG specialist reckoned a new turbo as the old one was over boosting. Me, my dad and my brother all reasoned that if the turbo was overboosting, then it was certainly fine. If I remember correctly we narrowed it down to 3 things.

1 Intake pressure sensor
2 Wastegate sticking
3 A control valve that was operated by vacuum pressure

Hmm, well it can't be the turbo or wastegate as they are both only a few months old, can't be the control value either as that was replaced.

Do these cars have intake sensors?

Why don't you turn the actuator down one turn and see how you go?
I had the same problem on mine once and that cured the problem.

Hi Danny, how you doing buddy?

Ashok suggested that too, unfortunately a few months back when the issue started I tried that. Took it right back to 15 psi and within a week it was doing it again...

Why don't you find yourself another Known good MAF and throw I on temporarily to see if anything changes. May want to dump that air filter first though...

I would fit a manual boost controller and then you will know the BCS isn't spiking.or fit a EBC if you can afford it.

They have a sensor on the intercooler which I believe is an atmospheric pressure sensor they also have the map sensor in the intake pipe

I would imagine there would be a pressure and temperature sensor after the intercooler. Turbo Diesels do and I don't see why Petrol should be different!

All good here Alex :) sorry for late post been moving flat lol

Was the car doing it before you had the turbo done? Or is it a new thing?

Hiya Danny,

Glad you're well :thumbs_up: Yep, the car was doing it before the new turbo and new TCV. Something isn't right. It did it again this morning, just the once.

The strange thing is, is that it always does it at around the same point of my journey, I do a lot of hard driving down the country roads once the engine is warm, then join a main road about 30 minutes into the drive, so normal driving resumes with traffic, then I take a roundabout to join the M3 and that's when I notice I've lost boost - Always after hard driving then 10 mins of calm driving. It's very strange!

I've seen extremely similar symptoms with both of my Mondeo TDs (Yes, I really am comparing an 89bhp paraffin-burner to a thoroughbred petrol turbo.. because its a turbo-car specific issue)

It was caused by a small valve on the fuel pump which opens to increase flow rate when the turbo comes online at (in that car) 1600rpm. Fresh from cold it worked fine, when fully warmed up it worked fine if constantly adjusted. After 10 mins of driving at a steady throttle setting it would stick and when I next opened the taps nothing would happen

(As opposed to something slowly starting to happen in an only moderately interesting way, which is what Mondeo TDs excel at)

So does the T4 fuel pump have a valve that opens with increased boost? possibly solenoid controlled? A new solenoid fixed both my cars when it occurred.

Hmm interesting. I don't think there's a solenoid on the fuel pump but surely if something were sticking there would be a misfire sort of feel rather than a perfectly fine car that gets put in limp mode?

Does anyone have any info from diagnostics in VIDA/DICE that determines what triggers limp mode?

I've ruled out MAF for now in the theory that when MAFs go they tend to either work or don't, they aren't intermittent in the way that this problem is.

Gonna give the pressure sensor on the intake a good clean tomorrow before work, see how it behaves.

I honestly dont know how it'd manifest - I've never even driven a T4 let alone owned one.

All I can say is that on my cars, the manifestation of a stuck fuel pump valve was a smooth and steady total lack of performance. It really does sound like the symptom of some sort of failing mechanical device.

Have you ever changed the Fpr?

Like Dx said, sounds like fuel related or air leak

Would I not have cold start issues if it were the FPR? Not changed that yet though no...

The systems tight, no leaks anywhere, most of the hoses got pulled off and inspected when my turbo was replaced and I've checked most of them myself, plus surely an air leak would just give me less boost all the time?

Boost always peaks at 1.35/1.4 bar WOT until the 'problem' trips limp mode. I assume a leak would give less boost/intermittent readings?

Fpr doesn't mean cold start issues only.
Mine used to start fine hot and cold but changed anyhow.
After that it felt so more responsive.

The only way to check for an air leak would be with a smoke test to be a 100%

I've had air leaks and still running on 18 psi boost, come to think of it I got an air leak on the way home from Gatos once and the car went into limp mode.

The ecu might notice after a good drive then goes to base 0,6 bar if I remember rightly.

Have a word with Ashok about Fpr and air leaks even the slightest air leak could cause a nightmare lol

We've exchanged 18 emails over the last 24 hours trying to work this one out lol. Gonna get some Wurth MAF cleaner on order, give that a go and pop it in for a smoke test on the weekend, along with the pressure sensor clean tomorrow as a first point of call :thumbs_up:

Don't know if it's any help Alex, but I know that sometimes if the problem clears by the time you go to get codes read it doesn't always keep it stored. (I've had this on mine)

Does the problem remain the same until you turn the engine off and back on? If that's the case if you can get it to happen again while your this way pop by and leave the engine running and we'll see what DICE shows?

Just a thought.

Happened again this morning - 10 minutes into journey this time, only happened the once though.

Would have popped by Matt but had a company meeting this morning so had to be in on time. Plus, another 40 odd minutes of driving with 0.5 bar would have been horrible lol

lol - put up with the drive or put up with the problem ;)

Lol, had I been able to stop at yours I would have put up with it.

Strangely, it never does it on my way home. I'm logging the short term and long term fuel trims on torque pro at the moment so will be interesting to see if that shows anything.

Update on this.

Happened again this morning.

Took it back to Volvo after work and did a code test. Apparently my battery needs replacing ASAP so £49 later for a gen Volvo one that's sorted. Also found faulty signal on camshaft reset valve.

Not sure if that would put it into limp mode but it's something so guess I'll start looking for those lol.

Update on this....

Well, no update really - More money spent, problem still persists :(

Put my brand new MAF in last night, got limp mode twice this morning, same as yesterday.

Parts replaced in last 6 months, all brand new, all Volvo.

Turbo
Coil packs
HT leads
Spark plugs
TCV
MAF sensor
MAP sensor
VVT solonoid
Thermostat

I even took boost down to stock for a week and still had the same problem so it's not an over boost issue.

I'm now a bit stuck, as mechanically, I can't think of anything else that can cause this! It's at the stage where I would just be replacing parts for the sake of it and even then, I'm unsure of what I would even replace next!

Any ideas anyone? I'm desperate now lol.

I see in your list no O2 sensors replaced and the motor has done 166,000 !!

I don`t know how long you have had the car miles wise but all the fuel system major parts should of been replaced including the O2 sensor at around the 100,000 mark for Preventative Maintenance and especially for reliability........but of course if one just waits for problems then so be it!

Having said all the above i never always agree with Mitch but this time even as early as post number 2 he states actuator adjustment...

Although you say it was set by Volvo the proper way...ok, the proper way but i believe that the actuator is set too tight and as Mitch says it will give Limp Mode for a time until you use lower boost for a while to give the ECU chance to reset itself...

1.35bar = 19psi........1.4bar = 20.31psi which is too much for a P2 2litre motor unless more modified to overcome problems...these motors have 2 boost sensors to keep the motor safe and you turn it up so it complains and gives you Limp Mode.........On a P1 motor it is ok as most is forged so safe up to 26 / 27psi i believe Tommy blew his T4 up at that......

The map you have should be set around 16psi and also will delete the boost limit but then you have over ridden that by too much adjustment.

Why don`t you just turn it down to standard setting and then find out what the problem is, at least then all is set how it should be!

The chart tells you what settings ...

Good Luck!

.............................
............................

Just read down to stock boost bit......but keep it there until you find what is what!...

What Turbo did you replace the old one with?...and are the compressor wheels inside the standard size or was it an upgrade?

..............................
................................

You are really getting down to the nitty gritty, and things which should be ok may not be so you have to check everything sensor wise!

Have you checked the Knock sensors on the front of the engine under the manifold ...they are bolted on and have to be torqued to the exact amount and at the correct angle on the block otherwise when the engine knocks or detonates the knock sensor may just to easily put the ECU into limp mode...

Hi Keith,

I've had the car since it was on 129k, the O2 sensors were replaced at around 115k IIRC by Volvo, I've no reason to doubt the service history since it's got a lot of it! The fuel pressures been tested and come back fine so I would assume the pumps OK. Injectors are fine. Fuel pressure regulator has been replaced since I took ownership of the car.

IIRC Ashoks map is set for 1.2 bar and is expected to reach 1.3/1.35 bar with an exhaust system, which mine has and the torques progressive. I think the whole P1 is stronger thing is massively over exaggerated so I'm not too worried about it going pop, it's not an off the shelf map. Compression is near enough spot on so I would say it's a healthy engine - However, due to the mileage now I have a complete rebuild planned for this year.

I've no reason to doubt the actuator wasn't set-up correctly since my uncle only gives it to the master techs, he doesn't let the others work on mine.

Also forgot to add, when I first got the car back with the new turbo fitted I kept it on standard boost for around two weeks whilst giving the turbo a chance to bed in before cranking it up to suit the map. During that time this problem was still happening. About a month back I also wound it back to standard and it continued to happen....

EDIT: Turbo was replaced with a new, genuine Mitsubishi 14T, supplied from Volvo over in Sweden and fitted at Volvo.

So your all ok O2 sensor wise and fuel wise......

The P1 thingy is not really over exaggerated unless one has owned one and you see how much a thrashing they do take everyday and i mean thrashing only then can one form an opinion.

Yes, the P2 can be ok....but not as standard...this is the important thing that i get pulled over about.

Did it do limp mode before the new turbo?

Is the turbo exactly as what you had ....maybe the actuator diaphragm and spring are not right for the turbo!

I still think as you have a map set to 1.2 then the turbo at std settings it is too much boost.....try it at the minimum on the actuator arm, go as low as you can to try it.....

.............................

Nothing to do with your motor but i am down your way Horndean to get a remap for my Merc in a couple of weeks.... bit of a way from Dover for me so i hope it`s worth the effort...Lol

........................................
...........................................

Strange everytime i ask you a question when i read your post then the answer is there .....i think you must get all things correct first ....so try the Knock Sensors...they do go wrong!

If i told you i was driving my first Volvo for 5 yrs until i knew the pinking was those sensors you would never believe me...i was then 1986 learning Volvos and never knew what a knock sensor was....

Yep, it went into limp mode before the turbo got replaced and even on the old TCV. The turbo was a part for part replacement, the waste gate comes as apart of the turbo assembly so that's brand new. I'm not sure if it's the same or not. I would be surprised if they fitted anything different.

http://i1158.photobucket.com/albums/...ps2148a9a8.jpg

EDIT: Nice, Horndean is the next village so only about a mile away. Where are you getting it mapped?

Getting it mapped at PCS ...Prestige Car Services

113A London Road
Horndean
Waterlooville
Hampshire
PO8 0BJ

...................
..................

Nice turbo.

Am i right in remembering you had a new engine or another engine put in some time back....all the more reason to check the knock sensors even if for piece of mind...

Ah, that's still technically Clanfield, just up the road. I do my 0-60 tests up there, you'll see why when you get there lol.

Nope, original engine here.

I'm probably talking nonsense but Was the waste gate replaced?

Also does the t4 have a n75 valve? Could be that?

Waste gate is apart of the turbo unit. All got replaced.

T4's have a TCV (turbo control valve/solenoid) rather than a N75 :thumbs_up: