'Limp Home' Mode

[JamesT5]

Anyone know whether Limp Home Mode on the T5 just limits RPM or alternatively, does it physically stop the car going above a certain speed?

Regards

James

[M-R-P]

Oh dear, what now?

I believe it limits revs/power.

[JamesT5]

Oh dear, what now?

I believe it limits revs/power.

Well I went to overtake on the Motorway on my way to Southampton and so I changed down a gear to get some boost as the traffic had slowed right down (one of those I got boxed in scenarios). Anyway, as I did so the power just died and I had to get in to a higher gear to accelerate away but gradually. I tried it a couple of more times today on some quiet roads and the same happens. Oddly, speed isn't limited and I was able to hold 70mph quite comfortably on the Motorway.

Now, I think I know why this is happeneing and that's because the sender unit in the car is faulty so the fuel gauge sometimes reads nothing. Therefore, because the car doesn't know how much fuel is in the tank the ECU has popped the car in to limp home mode (I suspect), in order to economise the fuel useage just in case the tank is empty.

Oddly, my OBD2 reader is saying there are no fault codes which is odd because limp home mode should show up on the reader. Anyway, I'm going to have to book the car back in to another garage and hope my second hand replacement sender is ok and then I can get rid of limp home mode - it may even reset itself once it knows the fuel levels are all ok.

Nothing will get done until Friday though as I won't be paid until then. Watch this space....

Regards

James

[jardon]

Limits power e.g: pedal to the floor and 5% ETM/no boost. Not rev limiting so far as I've experienced.

Edit - one of my senders doesn't work either (I think the one on the swirl pot as the pump's been in and out a lot) but this limp mode doesn't happen to mine. Interestingly I have had limp mode a couple of times when it's over-boosted with the silly actuator (though not for months) but there's never a code stored. My fuel gauge reads higher than it actually is so I fill up at 200 miles on the trip meter.


Edit 2 - your theory sounds plausible but I would be interested to hear what happens when the sender is working.

[JamesT5]

Limits power e.g: pedal to the floor and 5% ETM/no boost. Not rev limiting so far as I've experienced.

Interesting. I definately have rev limiting going on although it differs from one gear to the next, I haven't yet pin pointed a pattern to this so I may have to go out for a spin tomorrow on a quiet road and experiment with it, although I'm certain this is linked to my faulty sender.

[silverhorse]

Is it running rough, or still as smooth as usual, but just down on power?
Mate of mine had this on his car (admittedly not a Volvo), and turned out to be an injector clogged.
Power was limited but you could still cruise at 70. Could not rev very high though.
A symptom of his was rougher running and a bit of excess smoke.

Sometimes it's better when a bit just falls off, rather than something happens that you cannot see or figure out what is wrong. At least you can replace what falls off.

Good luck, and keep us posted.

[glock19]

Fuel sender won't give you this problem. If it's serious enough, then you get a CEL.
When was the last time the air-filter has been checked ?
Is the BCs/TCV knackered ?
Last but not least, a clogged up catalytic converter gives no boost too.

[JamesT5]

Fuel sender won't give you this problem. If it's serious enough, then you get a CEL.
When was the last time the air-filter has been checked ?
Is the BCs/TCV knackered ?
Last but not least, a clogged up catalytic converter gives no boost too.

I'm getting boost and the turbo is whistling away but it just cuts out when I push it hard. It cut out at around 4000 rpm then on another occasion around 2500 rpm, so who knows but I believe this is related to the sender.

I'll see what happens when I get the unit changed over and I might just use a different Volvo garage.

Regards

James

[M-R-P]

What about the pressure sensor in the intercooler? (I think that's where it is) if it's gone wonky, could it be over-reading and causing boost cut?

[JamesT5]

What about the pressure sensor in the intercooler? (I think that's where it is) if it's gone wonky, could it be over-reading and causing boost cut?

I took it for a trip to town earlier and gave it a thrashing up the road in 1st gear and managed to redline it. Silverhorse could be right with the clogged injector theory but I'll do a bit more experimenting to find out.

[M-R-P]

Boost is limited in 1st to protect the engine, you wouldn't have boost cut in 1st.
It might be worth checking the hoses to and from the BCS, especially the one that goes to the wastegate actuator.

[bubba_1986]

Sounds like a goosed bcs. I had same symtoms years ago and it turned out to be the bcs. Worth maybe trying to borrow one and try before changing it. I'm 95% confindent about this :-)

[jardon]

I have a spare bcs if you want to try it - can post tomorrow and be with you by Thursday.

[JamesT5]

What's the BCS, this is a new one on me...? Boost Control Solenoid?

[Mongo]

If bcs is broke it will be running 0.5 bar at max. Check the bcs pipes to actuator and pipes make sure there not split also give the plug a little clean. Bcs is located ion the airfilter box.

[M-R-P]

What's the BCS, this is a new one on me...? Boost Control Solenoid?

Yep - Boost Control Solenoid.

Attatched to the outside of the air box. It has 3 small rubber pipes and an electrical connection. check the pipes over, they go brittle and split at the bends or where they rub on the engine. If the one to the actuator has split, it will overboost as it can't control the turbo properly.

[bubba_1986]

When mines was gubbed it was certainly boosting higher than 0.5 bar. Would boost at I reckon 1 bar for a slight moment then cut off. Was diff in each gear as you have described. Get it changed and I'm sure all will be well. They are not that ex's pensive to buy new anyway as far as I remember

[JamesT5]

Thanks guys, I checked the hoses and there is no sign of cracking. I'm going to drive it around for a day or two and try red lining it in the lower gears and then seeing if I get any problems in higher gears too. Today, I managed to get the revs up pretty high in 2nd gear with no issues so I'm going to see if this is one of those things that comes and goes and then trouble shoot from there.

I'll keep you posted!

Regards

James

[JamesT5]

By the way, is it me or do I have the most problematic T5 on the forum...?

[MattM]

By the way, is it me or do I have the most problematic T5 on the forum...?

I dunno... mines been pretty bad in the year I've owned it.