We've just picked up a handy '98 v40 T4 and I noticed on the highway last night I tried to open it up a little and there was a very sudden loss of power. Once the revs dropped back down it would seem to be ok.
I sort of limped it home as it did it twice. I then put it in neutral while parked and revved the engine to see if I could get it do it again. It seemed ok.

I've rifled through the paperwork and fould it's had a new fuel filter and pump put in less than 1000kms ago. Air filter looks pretty new.

I don't know how to find error codes at this stage.

Where's the next place I should look?

 

Is the check engine light on? If it's a misfire due to hairline cracks on the coils or spark plug wires it should set a code.

Do you have a code reader? Are you in the UK? I'm not sure where to pick up a cheap code reader there. In the US we go to Harbor Freight. Or really cheap you visit the chain auto parts stores like Autozone and they will read the codes for free.

 

Took it for another drive on the exact same stretch of highway and put my foot down and it behaved itself.
No check engine light. There is a work receipt for a new coil, as well as a full service also. I inspected the MAF sensor and it looked very clean. Gave it a quick spray anyway.

Will keep an eye on it, I expect the problem to reoccur at some stage.

 

Problem hasn't reappeared, I have no idea what fuel the previous owner had in it at the time of sale but ran through some 98 after cleaning MAF sensor.
So far so good, fingers crossed.

 

Check the rubber hose going to the throttle body from the top of IC.It is known to crack and it will let boost escape.Could be a lose clamp as well at any of the hose location seeing how your problem comes out when you getting on boost..

 

would you believe it was a faulty fuel gauge?
The gauge was showing two bars and fuel light hadn't come on when the car totally stalled on a steep hill in an intersection, my sweetie-pie was driving to work.
I thought the car had **** the bed until she told me she'd put about 520kms on it since filling up. This was after we had it towed to the mechanic.

Sure enough he put in some fuel and she came back to life.

Not gonna bother fixing the fuel level sensor. We'll just fill up when it gets low.

 

3 months later and a very similar event has occurred. We were just driving the highway home when the car lost all power, had to limp it over to an off ramp. The thing is still idling the whole time, just almost acceleration.
I figure it's the fuel gauge issue again, although the gauge is sitting at HALF. It's not my daily car so I'm not familiar with the refuels etc.

We call the roadside man out and fill it with 10 litres or so of petrol. Voila, she is running perfectly again.
Drive maybe 4 kms to nearest petrol station and I expect to put in about 50 litres of fuel. Nope. 35 litres before it tops out.
Car runs sweet the 15 or so kms til home.

So it can't just be a faulty gauge reading now can it?
Clearly something is amiss and it's going into a limp mode until it gets filled with fuel.

Like I said, it had pump and fuel filter replaced just before we bought her.

Anybody got a clue where I should look first?

 

The way you describe the situation it really sounds like a low fuel issue. I would fix the known problem before trying to find an unknown problem.

 

that's what the mechanic and I both figured last time, no fuel - faulty gauge.
But this time when we filled it up right after the breakdown it only needed 35L to top out. On a 60L tank.

therefore it wasn't empty. just acting like it was.

 

It could be coincidental that adding fuel seemed to change the behavior (could have been the cooling off or just waiting for the fuel to arrive that "fixed" the problem temporarily). But if adding fuel does help, I'd start off looking at the only things that could be affected by adding fuel.

That would include the fuel pump and/or in-tank pick-up. I think the easiest test would be to see if you have proper fuel pressure. If the pressure is low, then suspect the fuel pump. Otherwise, it sounds like a fuel flow issue, where increased flow reduces pressure, but very low flow allows it to return to normal (or close to it), as evidenced by the fact that the car will idle OK after refusing to run at speed. I see that the car has had a new filter and fuel pump recently - it would be helpful to know if the car (while being driven by the previous owner) was doing the same thing prior to the FP and filter change, or if perhaps the symptoms were different (which would make me suspect the new fuel pump / pick-up). There's always the possibility that the new pump and/or pick-up aren't the right one for the car - if the pick-up is too short, you'll have exactly the symptoms you describe (fuel starvation when the fuel gets low, though it should occur at about the same point EVERY TIME, not randomly).

Of course, check for codes to see if there are any clues there.

 

I've whipped the pump out. It looks like it's the correct part at least. Like I said, it was done a month before we purchased the vehicle.
The filters look ok.
I've cleaned the fuel level sensor.
I guess next step is getting fuel pressure looked at.