Hi every one ,

I need some help again , i have a 98 s40 T4 . it started to judder recently again , only under full throttle . i was reading on other forums that it be the wastegate / dump valve ,

now - could somebody explain to me the diffs between . 1.) Dumpvalve . 2.) wastegate.

and what does my volvo have ?

Could a falty wastegate/dumpvalve be my problem ?

Thanks !

hi,

and no reply's yet ,,,im still struggling.

The wastegate on your car recirculates the air back into the inlet side of the turbo when you lift off the throttle. If it was playing up then you would loose boost as it wouldnt be able to hold the pressure that was generated. I would expect a light to come on though if you car was having problems with the boost.

What fuel are you using as when I tried my T4 on tesco 99 ron fuel it caused a judder under full throttle and as soon as I switched back to Shell Optimax it never did it again. Could be worth swapping to a different fuel station(dont know what ones you have over there). If that doesnt fix it(it will take 2 or 3 tanks for the ECU to adjust) then it could even be a coil pack playing up.

I had what I think is a similar issue to you.

The Volvo shop I went to replaced my fuel filter and put in a new set of plugs. So far it seems to have fixed the problem.

Well sofar it only happens when under load - or full throttle.

The fuel here (wich they say replaced optimax) is shell V-Power 95. Worth a shot !

But what impact does fuel have on this ? could it be that the internal wastegate is not functioning like it should hence causing the engine to overboost and the ecu cutting the fuel ?

Sorry for all the Questions ! :)

I'm pretty sure that a waste gate and a dump valve are the same thing.

Had the same prob' as yourself recently, changed the plugs, runs fine now.

A waste gate or dump valve prob' will not cause hesitation under load, but you'll notice the rev's drop quicker when you lift your foot off the throttle.

A leak in the vacuum pipe for the dump valve will give an irregular / rough idle.

Hope this helps.

Stu.

I have a similar problem on my '01 s40 1.9t, under moderate to heavy acceleration i have a judder and an occasional buck. had it diagnosed, o2 sensor #1 was faulty also a misfire in cylinder #2. changed the plugs and wires but not the coil packs, and replaced o2 sensor. it is better but not gone. cylinder #2 is still misfiring.

do i need a good fuel injection cleaning service or should i just replace my injectors? i have 112k on the car and i really don't know how long fuel injectors usually last.

:liebe011:

Hi ,

I tried the injector thing .. didnt replce them but they was sent in for n clean . still the same problem. im hearing some people saying it could be the trubo overboosting the engine , the car has n build in safety and cuts the fuel supply , hensing the judder ? does that make sence ?

I have a 1998 S40 T4 which has a judder under load, I have changed the plugs and leads. I have taken the whole intake system apart and put it back together checking for broken vacuum and breather pipes.
But I still have had no joy with correcting the problem, I have a obd2 code reader and it is not showing any fault codes.
Does any body have any ideas what this could be?

I had a judder under full throttle on my T4, but after lots of thrashing, it seemed to rectify itself, although I needed to get some new tyres.

well, you should definitely check coilpacks. I mean, even if they don't have any visible cracks on, they could be bad.
Misfire is usually when plugs or coils are done.

Also, check for boost leaks. And if you don't have boost gauge, get one.
Dump valve is good on these cars and doesn't brake down easily.

Wastegate could brake down. But usually WG actuator is a weak point. It gets loose. So, tighten it a bit.
When BCS, boost control solenoid, goes down, you should get error codes.

I still have judder problem, I have replace plugs, leads, both ignition coils and the MAF sensor. I still have a power loss problem at 3000rpm along with juddering if accelerating hard. I also have a juddering problem in low revs now when pulling away. Also when I stop the revs drop right down to almost a stall, it has not stalled on me yet but it is close to it.
I have plugged a code reader in and I have P0172 & P0172 pd fault codes, from searching the internet I have found that it is running too rich. Any ideas people?

I would guess after everthing you have changed your aft lambda sensor id knackered. Do you have a engine light on the dash lit up?

There are no warning lights on.

Wont be the lambda sensor then. Does the engine management light light up before you start the car, just to check that the light is working?

There is no engine management light in my car, I have taken the dials out and checked all of the bulbs. The Lambda light comes on before the engine starts but it goes out straight away.

I changed my fuel filter yesterday because I don't know when it was last changed. I cut the old one open just to see how dirty it was and it was black. The new fuel filter has not stopped my judder problem but I borrowed the turbo control valve out of my mate S60R, identical unit but just a different mounting bracket. Anyway took the car out for a drive with the s60 turbo control valve on it and it was fine. No juddering smooth acceleration right the way to the red line (not that I usually go that far in the revs). So it must of been a over boost problem and the ecu cutting the fuel.

I still think that you have torque steer and that you are misinterpreting it as a judder. try not to leave the lights with the turbo at full spool. how about gently driving through and then pumping it. i bet that would clear it right up. nothing to lose. give it a shot. also cheaper that replacing any good parts with good parts. :thumbsup: