54 plate V70 throttle issues

[R3dbvll]

Could it be the fuel filter? I don't know when it was last changed (wasn't done at the last service), and the car has done over 170k.

As the tank is draining, crap from the bottom of the tank is being picked up, maybe?

[Chris_Rogers]

It seems you have the Bosch throttle body which is not known for giving problems so I'd not rush to replace it.

Apart form normal service items such as spark plugs, air /fuel filters etc. I can't think of anything else which would cause the problem your having.

If the issue is related to fuel level then I guess adding some fuel and seeing of the problem goes would prove the point.

The 'Reduced Performance' warning' should reset itself after 3 drive cycles (cold to hot engine) if the problem's gone.

[R3dbvll]

I disconnected the battery, which reset the problem.

I just restarted the engine, after leaving it for ten minutes. Started fine, ran fine for about 2 minutes.

The rev counter sits at just over 700 which seems a little low. Gradually the revs drop. With the AC on, the revs drop a bit with the compressor coming on, which seemed to drop the revs too low. The engine responds by giving the revs a kick, which then drop again, until misfiring starts to happen, and the engine dies.

Fuel filter? General fuel tank problem? Throttle module (maybe needs to have a software reset after fiddling with it?), coil pack?
The plugs were replaced with Volvo ones a few days ago.

Something else as well:
When the car was serviced last week, they did a read of all the codes, and a refresh.
There was only one code that came out, and that was for a faulty air quality sensor.

[Chris_Rogers]

I'd suggest you add some fuel and see what happens, it does sound like lack of fuel and not just an idle issue.

[R3dbvll]

OK, so I went and filled my 5 litre can with petrol, came back, made sure the engine was still dying.
Then put the 5 litres in. That isn't much I grant you.

Engine still died but it took a little longer. I also put some Redex in as well.

For the hell of it, I went for a drive. Went up and down a for 60mph stretches. Smooth as glass, drove beautifully.

Then I drove along some much slower roads, and thats when the stuttering came back. As if the engine is being starved at low revs. If you can keep the revs high (i.e. fast driving) it seems OK.

Might this point to the fuel filter? I really have no idea how the fuel system works.

What I'm puzzled about is how after I cleaned the throttle body, it all seemed to work OK. Would the high ambient temperature be a factor at all (fuel evaporation)?

What I need to do next is fill the tank right up and see what happens. Like this, I really can't trust the car on a long drive to the south of France with the family (which is happening in 19 days!). If I could just nail down the area that would help.

Certainly, it seems that the idle revs are very low - 700. Then it dips below that and the stuttering/misfiring starts to happen.

Any more ideas?

Thanks!

[Chris_Rogers]

Lack of fuel at low revs does not make any sense, the only thing I can suggest is there is an air leak into the intake but to cause misfiring I'd expect it to raise a MIL lamp and for the leak to be fairly large.

Have a look at all the joints on the intake and all the small vacuum pipes for splits etc.

Does the car have an assisted air valve?
This is would be between the throttle and the intake, it allows air into a trunking feeding air around the fuel injectors on some engines. If it's stuck open it could account for the problem.

[R3dbvll]

Originally Posted by Chris_Rogers

Lack of fuel at low revs does not make any sense, the only thing I can suggest is there is an air leak into the intake but to cause misfiring I'd expect it to raise a MIL lamp and for the leak to be fairly large.

Have a look at all the joints on the intake and all the small vacuum pipes for splits etc.

Does the car have an assisted air valve?
This is would be between the throttle and the intake, it allows air into a trunking feeding air around the fuel injectors on some engines. If it's stuck open it could account for the problem.

Hmm, I don't know. What I look for to know?
I think I will take the car to my local mechanic (not a Volvo one, but good anyway), and ask them to have a go at finding the problem.
No harm in having the filter replaced anyway, I suspect it is long over due.

Another thought - could it be the catalytic converter? It was replaced before I bought the car, using a non-Volvo part. When I looked at the car, the cat was rattling badly, so the dealer had it replaced.

I dug up these interesting posts (below). The issues sound very similar to mine, and suggest a fault fuel pump or bad hose:
http://turbobricks.com/forums/showthread.php?t=250114
http://www.matthewsvolvosite.com/for...hp?f=1&t=28600

[R3dbvll]

I know this post is a few weeks old now, but I think I can bring this to a conclusion (I hate reading through forum posts and finding no conclusion!).

Long story short, I took the car to Martin Matthewson Volvo (independent) in Basingstoke. That is a 40 minute drive from here.

It was well worth it. They are fully equipped to handle any issue software or hardware, and were happy to take the car, and figure out the issue. It turns out that I was in the right area, that it was a fuel issue.

It was, in fact, the fuel pump in the tank that caused the problems. The issue would only happen when the tank was a third full or less.

Anyway, the problem was fixed, and I am very pleased.

A can give a whole hearted recommendation to these guys - kept me informed all the way, discussed various options including fitted second hand parts etc. Well priced, good quality work.