Engine turning off when accelerating. Help!!!!

[Marsha]

Hello there,
I have a huge problem with my S40 52 1.9TDi.
Recently, when driving to town the car started to jerk and lost power, I had to engage the highest gear possible so that the engine wouldn't turn off completely.
I changed the fuel filter as I did not know when it was last time replaced.
I thought that would resolve the problem.
Today on the way from work, I had so much stress like never before, on one of the busiest roundabouts my Volvo just refused to work, i put it on 1st gear to get the car rolling and the more i accelerated, the less willing the engine sound. It looks like i pressed the accelerator and the torque was dropping down.
I managed to get out of the roundabout at the speed of 2 miles per hour pressing accelerator hard so that the engine does not turn off again. I managed to get the 2nd and again I tried to accelerate, the car wouldn't respond much and I hardly made it home tonight driving slowly having the emergency light on all the time.
It kept wrenching/jerking all the time when I tried to accelerate a bit more :-(
All filters have been replaced recently, there is a new fuel, oil and air filter.
At first i thought that the clutch was slipping as this is what it feels when you release clutch and press accelerator, I was told, however that it is not the clutch. A mechanic, good neighbour of mine had a look and stated that it cannot possibly the clutch.
By the time he decided to have a proper look into my car later on, things got back to normal and the car would drive like a star again.
It has been 5 days and the car lost the power completely and did the same thing to me on my way home tonight.
It is not the turbo as it is working fine.
Please help me, I am at the end of the tether with this car, it has really been causing troubles and developing minor and major faults on a regular basis.
Has anyone had a similar situation? (My Volvo is most likely to turn off completely only on 1st gear unless I accelerate on any other gear, if i do try to accelerate normally on second or third gear it would nearly turn off - I have to takk the foot from accelerator and press clutch and try to engage it on the next gear so that it does not turn off)
I bet that now, after few hours on the driveway I can put the key in, start it and it will drive well again.
The trouble is, it is only till next time it happens and according to me it is most likely to happen sooner rather than later!
Please help! I am only a woman and petrified to drive into town now!
Kind Regards,
Marushka
P.S. I am sorry, my English is probably not good enough but I tried to describe the fault my car developed to the best of my ability :-(
And just so you know, no warning light would come up when it happens :-(

[evan]

could it be air in your fuel lines evan

[rippedoffagain]

MAF sensor? I don't know much about diesels, but if the MAF is playing up (as mine did once) pressing the throttle can make it give up.

[Marsha]

Originally Posted by evan

could it be air in your fuel lines evan

I am so grateful for the tips.
Just to let you know that 2 hours after I hardly got home, i started the car to see what happens and it drives like a dream again!
How could air get into the air lines, Evan?
I am sorry, please do not think i am silly by asking but I have no idea about cars and how they work.
I am only good at cooking and washing up :-)

[Marsha]

Originally Posted by rippedoffagain

MAF sensor? I don't know much about diesels, but if the MAF is playing up (as mine did once) pressing the throttle can make it give up.

Hello,
Thank you for your help.
Could you please clarify what MAF is and what is its function in a diesel car?
As I stated before, i am no good with cars. I know how to replace certain things such as fuel or air filter or battery but I am not very familiar with technological vocabulary.
i am sorry :-(

[rippedoffagain]

Some cars have a MAF (Mass Air Flow) sensor, some have a MAP (Manifold Absolute Pressure) sensor. Both serve a similar function. They measure how much air your engine is drawing in and use that measurement to calculate how long to open the fuel injectors for, thus keeping the fuel to air mix close to ideal.

If a MAF sensor fails completely, your ECU (Engine Control Unit - the computer that looks after your engine) would tell you via a warning light on the dash. If, like mine did, it plays up and gives a seemingly valid reading but that is actually wrong, then the ECU thinks there is more or less air flowing than there is, so the injectors open for the wrong interval and your fuel to air mix is wrong. In that case the lambda sensor (the thing in the exhaust that does a final check of fuel mix by measuring how much oxygen is left unburnt) would usually complain, and so again you'd get a warning light, except that when mine played up I didn't get the warning light.

In my case the incorrect reading was caused by my MAF being filthy. A bloke from Green Flag took it off and showed me it, it looked like the inside of a hoover bag. He cleaned it, but it back on, and I was on my way.

As for air getting into the fuel line, this can if your fuel pump is weak or intermittently failing. It could be something as simple as a faulty relay, or something more drastic like a duff pump. As your problem is intermittent, I'd bet that if it is fuel pressure related, the relay is on its last legs.

It can also happen, I believe, if the fuel pressure regulator is duff, or if certain vacuum hoses as split or have become dislodged.

If the car has recently been allowed to run out of fuel, this can cause it too. Even after being refueled.

[Marsha]

Originally Posted by rippedoffagain

Some cars have a MAF (Mass Air Flow) sensor, some have a MAP (Manifold Absolute Pressure) sensor. Both serve a similar function. They measure how much air your engine is drawing in and use that measurement to calculate how long to open the fuel injectors for, thus keeping the fuel to air mix close to ideal.

If a MAF sensor fails completely, your ECU (Engine Control Unit - the computer that looks after your engine) would tell you via a warning light on the dash. If, like mine did, it plays up and gives a seemingly valid reading but that is actually wrong, then the ECU thinks there is more or less air flowing than there is, so the injectors open for the wrong interval and your fuel to air mix is wrong. In that case the lambda sensor (the thing in the exhaust that does a final check of fuel mix by measuring how much oxygen is left unburnt) would usually complain, and so again you'd get a warning light, except that when mine played up I didn't get the warning light.

In my case the incorrect reading was caused by my MAF being filthy. A bloke from Green Flag took it off and showed me it, it looked like the inside of a hoover bag. He cleaned it, but it back on, and I was on my way.

As for air getting into the fuel line, this can if your fuel pump is weak or intermittently failing. It could be something as simple as a faulty relay, or something more drastic like a duff pump. As your problem is intermittent, I'd bet that if it is fuel pressure related, the relay is on its last legs.

It can also happen, I believe, if the fuel pressure regulator is duff, or if certain vacuum hoses as split or have become dislodged.

If the car has recently been allowed to run out of fuel, this can cause it too. Even after being refueled.

Thanks a million!
I envy you having so much knowledge so whenever anything happens you can at least predict what the possible cause may be.
I have put your comment on the sheet of paper for the mechanic for tomorrow along with description of what has been happening to my car and will hand it out to him tomorrow, as my written English is somehow better than spoken :-)
I shall find out tomorrow (hopefully!) what is wrong with my car and should the fault be what you suggested, I will be ever so grateful!
I already owe you for a comprehensive explanation of what MAF is.
We learn something ever day, don't we?
Thanks again!
Marushka

P.S. I don't want to sound cheeky to ask for even more info, but since you explain the things in such an approachable way, could you please kindly advise, is that normal in these circumstances (Eg filthy MAF) that my car plays silly when the engine's hot only (it never wrenches when the engine's cold) and there are days when nothing wrong happens at all? I thought that should there be something wrong with a particular car part, the car would stop working or the engine would shut down until the remedial work's done and the faulty part replaced?
Feels like magic? :-) Today it is working fine, tomorrow it shuts off when the engine gets really hot? It happened to me today after I spent half an hour on idle and 1st gear in the traffic jam. What do you think???

[grass hopper]

worth getting the fault codes checked.

first things that spring to mind that can cause problems are a split turbo hose,one fails below the air filter box,this is the pressure side, and one close to the turbo on the induction side,this usually fails due to slight oil residue on it.

also the turbo control valve on the bulkhead can intermittently fail.

also the fuel pressure sensor mounted in the fuel pump can intermittently fail.

these might have been previously mentioned,not had time to look through all the posts

regards GH.

[Marsha]

Originally Posted by grass hopper

worth getting the fault codes checked.

first things that spring to mind that can cause problems are a split turbo hose,one fails below the air filter box,this is the pressure side, and one close to the turbo on the induction side,this usually fails due to slight oil residue on it.

also the turbo control valve on the bulkhead can intermittently fail.

also the fuel pressure sensor mounted in the fuel pump can intermittently fail.

these might have been previously mentioned,not had time to look through all the posts

regards GH.

The car has been connected to the computer and it did not come up with anything at all :-(
I have had no warning light on the dashboard either.
And thank you for the tips, they are very useful, I will suggest the mechanic to have a look into these parts tomorrow.
Kind Regards,
Marushka

[rippedoffagain]

A couple of tips, although sorry I might be too late.

If you are about to pay a mechanic to fix your car, never tell him what you believe the fault to be. If you say "My MAF sensor is bust", he may well put a new MAF sensor on, charge you a couple of hundred quid, and that might not have been the problem.

If it only happens when the engine is hot, then it could be a number of different things. A faulty fuel pump relay seems to be the common one. These are cheap and simple to replace, but it could also be one of your engine's sensors playing up.

I'm no top mechanic, and my understand of diesel engines is less than my understanding of petrol, but perhaps a temperature sensor is misreporting.

When you say the problem only happens when it is hot, do you mean when the engine is operating at its normal temperature, or is it actually overheating? Cars tend to die when they overheat too much, and then sometimes work again when cold. This can be simply down to readings from the various sensors, or in the worst case the cylinder head could be warped.

Is your coolant ok? It should be filled to the marked level and should be bright blue in colour.

What does the engine sound like both when hot and when cold? Does it sounds smooth or does it sound like a tractor?