T4 power loss and erratic idle

Originally Posted by NJH26

Is it cheaper for the dance than the sensor?!!!

Just had the chat with the garage - my rear lambda (SP?) sensor has been replaced and taken with it nearly all of the fault codes. This seems to have caused all of the issues and also explains why I've been going through fuel at a rate of knots. Also found that my fuel pre-pump isn't working properly but to be fair if it still starts I'd rather wait for it to break all together before shelling out another £800.

Ok, commented on this fuel thing in your other post in 40/50 forum... but maybe your garage isn't too bad if they sorted the lambda sensor jobby. But something seriously wrong with a quote of £800 for what sounds like a fuel pump change and I still haven't worked out what a pre-pump is. And everytime I write pump I keep writing 'pimp' and having to correct it, why's that is it a freudian slip or something???!!!

[timway]

Finally took mine into MRG chippenham last tuesday, picked it up yesterday.

Diagnosis was a faulty starter relay switch thingy (?) not totally sure what that is to be honest, I think its linked with the immobiliser. But apparently its known by Volvo to be a problem and they pay for 50% of the cost of parts and labour for cars outside of the volvo warranty but under 5 years old.

Apparently the faulty relay can cause voltage spikes which affects other systems like the DSA, and also cause poor starting etc (although mine didnt suffer from that). The cure involves replacing the relay and part of the wiring harness.

Anyway, mine seems to be fine now and seems to be running smoother without any of the hesitation under hard acceleration it was having before. As it was an intermittent fault it'll be a couple of weeks before I'm certain its cured but I'm pretty sure it is.

Apart from that, had to have one of the studs on the rear hub replaced due to it being cross threaded (not by me!) - that was £92+vat (ouch)

And £52+vat to replace a blown sidelight bulb!!! Because I've got xenon headlights they have to take the high voltage unit behind the light off to get to it so its quite a lenghy job. I tried to do it myself but gave up, and even my local garage wouldn't do it.

They also said my oil consumption wasn't excessive (about 1.5 litres in 3000 miles). So hopefully thats ok.

I had the new shape S40 1.8 SE as a courtesy car, found it very refined and quiet, liked the interior too, although the footwell was a bit cramped for my size 10's and no clutch footrest . But painfully slow.... it actually accelerated slower in 2nd than my T4 does in 4th!!! (I timed it) and also used more fuel (managed 30mpg over 250 miles, mine typically does about 31 on the same journey).
Very glad to have mine back anyway
Tim

[foggyjames]

For future reference, classic items to check when experiencing these kinds of problems are the lambda (hurrah!) and MAF sensors. Of course it can be a rather more esoteric fault than that...but these items are relatively cheap to replace, and easy to swap for a known-good example (respectively).

cheers

James

[timway]

Thanks Foggmeister

It seems like the DSA problem has been cured anyway, unfortunately not the loss in boost pressure - it happened again this morning, halfway through the journey into work it suddenly decided it wasnt going to go above 0.5bar . Definitely happens more in cold/damp conditions. I think the hesitation when accelerating hard may be the turbo "surging" - usually it only does it if you use about 80-90% of the throttle travel (but not if you fully floor it)- the boost keeps picking up then falling off again
I think I'll just live with it for now anyway, its not a major problem as it doesnt happen toooooo often.

Tim

[foggyjames]

If you can pin it down to damp conditions, definitely look at electrical components...including the ignition system. When was the last time it had a set of leads, cap and arm, for example? I'm going to look like a prat now if it's coil-on-plug!

cheers

James

[timway]

I think its coil on plug system, its only 3.5 years old with 60,000 so I'd have thought they should still be ok?
I think its actually more to do with temperature than the damp actually. Maybe the turbo is working "too" efficiently when its cold and overboosting/surging perhaps? My boost gauge peaks at 1.5bar between 3000-4500rpm which is a bit higher than I was expecting...

[foggyjames]

Coil on plug pretty much removes routine replacement of ignition components. Pretty damn slick. I fancy coil-per-plug (COP but on leads) if I ever run Haltech...COP is a bit of a PITA when the plugs aren't in the middle of a twin-cam head!

I doubt it's 'just an effect'...I suspect something is broken. Boost control solenoid maybe?

cheers

James

Ok this is me not actually bothering to look at the manual, car, anything but I had it in my head that rather than 4 coil packs the T4 had 2 coils, no distributor but then one cylinder gets spark for power stroke and the other on the same coil also gets a "wasted spark" at that point.

I am right?

Or is this another car entirely?!

Pete

[foggyjames]

I hadn't heard of Volvo running wasted spark, but it's perfectly possible. I think standard COP is more likely. They definitely use it on some of the 6-pots. Either way, I think we can reasonably safely say it's not ignition related.

It's most likely one of the engine sensors gone bad, and I'd start by checking the MAF against a known good one.

cheers

James

[timway]

Originally Posted by foggyjames

I hadn't heard of Volvo running wasted spark, but it's perfectly possible. I think standard COP is more likely. They definitely use it on some of the 6-pots. Either way, I think we can reasonably safely say it's not ignition related.

It's most likely one of the engine sensors gone bad, and I'd start by checking the MAF against a known good one.

cheers

James

I think it is running a wasted spark system, when I changed the plugs only 2 of them had what looked like coil pack on top.
I was thinking its likely to be something to do with the turbo boost control, like you said in an earlier post ? I'm not sure how to prove or disprove that though... I know you sometimes need to adjust the wastegate actuator after getting a remap, but I'm not sure if thats the case here.

If there was a problem with the MAF sensor, presumably I'd have other problems like poor starting/fuel economy/perfomance ? (I'm not). If I had access to another MAF sensor I'd give it a try though.

hmmmmmmmmmm