850SE won't stay started Help!

[jencrow1]

Got Volvo 850SE 1996 Estate, ( my 5th volvo) has run brilliantly for last 3 years, on 13th aug it decided to suddenly cut out, tried to re-start, would start up & then cut out as soon as you touched accelerator. Got it towed home, had a mob bloke look at it, he did all the basics, said it needed diagnostics, put it in garage on 17th august, mechanic is giving me the run around,
1st it was the fuel pump, ok, changed it, no difference,
must be split air pipes after the Mass airflow meter/sensor, changed them, no difference.
Now it's got to be the Mass airflow meter/sensor, changed it, no difference!
Now its the pipes under the manifold, they're a bit rotted, ok take manifold off & change 'em. still no difference.
trouble is this bloke isn't doing the work when he says he is going to, he's off, playing on the river dee. I've spent £500 quid with no difference to my car, & I'm beginning to think after a month he doesn't know what he's looking at.
Trouble is, I can't get car started, so can't take it to another garage. I did call another mobile mechanic i,n but this mechanic kept asking him, has he checked this or that, so he walked of the job.
Has anyone got any ideas what the problem could be? I'm beginning to think it's something really simple that's been overlooked. Am desperate to get my car back. Please guys any suggestions will be welcome Thanks

[FCPEURO]

The first thing you need to do is find out what codes in the computer are coming up. Without scanning the car and getting the codes, we will just be guessing like the bad mechanic is doing. Have you had the computer read?

[IceTurbo]

Throttle position sensor?

[jencrow1]

Thanks guys, will chase these up, also thought fuel pressure might be a problem, so will get all 3 checked out.