V70 2.3 T5 fluttery misfire

[Green440wedge]

I would appreciate some experienced advice.

Since fitting a new Bosch MAF a short while back I have an occasional fluttery misfire, typically in 2nd gear under light acceleration, engine warm. It doesn't do it all the time.

The old original MAF had started playing up engine cold, the car has done 120K miles. But it didn't have the fluttery misfire.

I had tried an Ebay MAF but binned it after a week, 5 year warranty, reputable Ebay supplier which refunded me. It ran terrible but again no fluttery misfire.

The car gives no fault codes on Torque. It drives pretty well overall, although the turbo seems to drop off over 4000 rpm under hard acceleration. Maybe that's just me.

It is running on a newish turbo valve and quality after market coils. Air filter and fuel filter are recent, and I ran some redex through it. It has done 20k on its plugs.

I'm not sure what is wrong. Has anyone had similar occasional fluttery misfire symtoms?

I wondered if it could be fuel pressure but I doubt it, it is normally ok. Could it be the electronic throttle unit. Or yet another faulty MAF???


I'd appreciate any experienced comments, thanks.

[VOLVOBOY]

Hi.
"Mmm !" Not an easy one.
What`s it like at idle ? Idle and light throttle are high engine vacuum. So I`d start my search there especially as the turbo has been touched. Which valve do you mean . The turbo waste-gate or the by-pass valve ?
At 120K I`d be expecting the by-pass valve to be past its best and the spring inside weak. That could be why the boost falls away at high revs.
The turbo control valve is a known weak point and I`d suggest that if a new one has not been fitted to do so.
Is the turbo waste-gate adjustment correct ?Check the vacuum hoses for leaks/ correct fitment and check the two non-return valves.
Have the correct spark plugs been fitted - should be the longer thread. Best to use only Volvo brand.
As it`s not happening all the time it may be temperature related or even fuel.
It would be just as well to change the fuel filter if it`s not been done.
Clean the throttle body. If it`s a Bosch unit it should be trouble free.
That`s enough to be going on with.
Cheers.

[Green440wedge]

Thanks for your comments. I replaced the turbo control valve 20k miles ago whilst trying to diagnose what was an initial MAF fault. I haven't touched the turbo itself other than to change the vacuum pipes. I also changed the non return valves. The plugs were the right spec. I changed the fuel and air filters.

I may clean the ETM again, it is Bosch as I recall, I did it 20K miles ago when I redid the oil breather system.

Today when the temp had got up to a quarter way it gave the fluttery misfire on engaging 2nd gear from 1st on steady acceleration from the lights. It only did it once. I took it up a big hill and overtook a truck and put the pedal to the metal in 2nd. It performed as it should, no flat spots and seemingly power was still there until about 5800 rpm when I changed into 3rd. On a dual carriageway I gave it some pasty upto 70 mph and again it performed well.

Whatever is at fault is intermittent. I have been filling with BP ordinary 95 UL.

Maybe the turbo components are wearing as you suggest. I haven't touched the wastegate adjustment.

Sometimes it runs as if it is slightly off tune, that is how I would describe it having had plenty of cars with distributors and points. Then after some pasty it seems fine.

I suppose its a 20 year old car. Maybe the best policy is to live with the fault and wait until something actually goes wrong?

[VOLVOBOY]

Hi.
Right. We can discount my first post as you`ve covered all of that.
It doesn`t sound like turbo either. If it pulls like that then there`s little to worry about.
Does it only happen on the initial warm up when the temp gauge is still rising?
Does the temp gauge reach half way with fully warm engine?
I`m thinking temp sensors possibly. A fluffy misfire seems more fuel/air related to me. An ignition misfire is more like a hard knock.

[harveys]

When the sparkplugs were changed did you use Volvo plugs or aftermarket ones.
Can you get live data for the front O2 sensor to see if it's running lean ?.
Can you get the MAF reading at tickover to see if it's the correct air volume data .

[VOLVOBOY]

Originally Posted by VOLVOBOY

Hi.
"Mmm !" Not an easy one.
What`s it like at idle ? Idle and light throttle are high engine vacuum. So I`d start my search there especially as the turbo has been touched. Which valve do you mean . The turbo waste-gate or the by-pass valve ?
At 120K I`d be expecting the by-pass valve to be past its best and the spring inside weak. That could be why the boost falls away at high revs.
The turbo control valve is a known weak point and I`d suggest that if a new one has not been fitted to do so.
Is the turbo waste-gate adjustment correct ?Check the vacuum hoses for leaks/ correct fitment and check the two non-return valves.
Have the correct spark plugs been fitted - should be the longer thread. Best to use only Volvo brand.
As it`s not happening all the time it may be temperature related or even fuel.
It would be just as well to change the fuel filter if it`s not been done.
Clean the throttle body. If it`s a Bosch unit it should be trouble free.
That`s enough to be going on with.
Cheers.

Apologies...
Typo. The sparkplug thread length should be the shorter 18mm

[Green440wedge]

Well that got me thinking. The plugs I think are Beru or NGK for this model, they have done 20k miles now, that is not too much but I could change them. I figured though that if they were failing that they would do so under load which they have not.

Maybe it is not a full misfire as you say, I have had that before on a poor coil earth, it was obvious and Torque identified the cylinder and fault, not the case here.

It has fluttered a quarter and half way up the temp gauge, it always warms up properly touch wood.

Today added some Redex. It hasn't fluttered at all.

Here are three photos of Torque at idle and at 2000 rpm, engine warm, and one at idle 1/4 way up the gauge. I can only get one reading for lambda, this being "02 1x2". My Haynes manual says there are two lambda sensors though? Torque is not giving a fault though.

Engine cold I get 0.4V for lambda, in fact it gives this at 1/4 way up the temp gauge, as you can see. Just checking again now on warming up again I get 0.4V nearly warm.....??

If this data means anything to you I would certainly be interested to know!

[barrybritcher]

they only like volvo plugs, I know that sounds like horse manure but it's true. I've tried NGK in every other vehicle but the volvo doesnt like them

[Green440wedge]

Who makes Volvo plugs and what is the technical spec of these plugs please?

[barrybritcher]

dunno but they are made in Germany