Been doing agency work for the last three months. Loads of different trucks to try, which has really built up my artic experience though I still tend to struggle reversing on bays in busy hubs if everyone else is in a rush or a shunter is watching. Had a job this week for one night - turn up, get the keys from under the bonnet, do the drive and return, park up and go home. Got there and its a brand new FM12 with 800 kilometers on the clock. (Wont be smoking or eating my sarnies in this one). Anyway, could I get it to pull away decently. Put it in gear, out clutch and no revs. It crawls away on tickover for a few yards, then suddenly bursts into life and roars off. Goes great after that until the first roundabout. Nothing coming, foot down and no revs. Crawls out into the roundabout upsetting the bloke in the black BMW who was nowhere in sight when I set off. Then it bursts into life again and I’m off. When I got to my destination I tried it in every gear I could to see if I could get it to pull away sharply without success. If I put the handbrake on it would rev away until I let the brake off and the it was back to tickover. Was I doing something wrong? or is there a special way or method to make it rev.
can we presume you were pulling away in low range as opposed to high. 
what gearbox was in the truck
the fact that you mentioned the engine racing when the handbrake was on and idling when the brake was released seems rather unusual to me. maybe related to a pto or something.
did the truck make any unusual noises or where there any unusual lights lit up on the dash.
i have not driven a fh for a very long time but if its a new truck it may have some sort of anti theft device fitted or similar that could effect it.
or am i just talking poop 
Just had a chat with Rikki about this one, and he had an idea which made sense to me too…
I don’t know if Volvo have ever fitted it, but some trucks have a gadget known as “idle-away” - the EC-series ERFs with the synchro-box spring to mind.
Basically, the truck sets the revs for you when you lift the clutch, so you don’t need to touch the throttle until you have started rolling…
…unfortunately if you do touch the throttle, it confuses the computer completely and you get results similar to what you describe above.
Could be wrong, but would make sense…never did get to grips with it myself!!!
Lucy, what are you two doing being still coherent at this time on a Saturday night?
Idle Away is a common feature in both diesel cars and trucks, and has been for some time, and I have never encountered that sort of problem.
However, what I have encountered is a system whereby that, from a standing start, unless you select either 1st or 2nd gear, the fuel flow is interrupted and the engine ‘hunts’. Not quite stalls, but neither does it want to go.
I presume it is intended to reduce clutch wear. The time when it becomes a real PITA is when running ‘bobtail’, a situation when you know it will happily take off in 5th, but it wont.
I have yet to drive a truck here that doesn’t have ‘Idle away’ 
But if that were the case it would accelerate ashe lifted the clutch, then once fully out the revs drop again untill the driver put his foot down 
the daf i drive has a device fitted that wont let the engine rev unless you start in 1st or 2nd gear, its ok once you are rolling but a right pain when empty or in just the unit
I had a very similar intermittent problem on an Iveco a few months ago, never did discover what it was. But it wasn’t nice.
It might be an electronic clutch saver,
I have fitted one to a scania that kept eating cluches,(Hire Truck!)
If you try and select any gear higher than 1st it cuts engine torque to prevent the driver slipping the clutch,
But also if you are riding the clutch you can not rev the engine until your foot is completely off the pedal,
A real pain to drive but has solved the cluch problem for the customers, so at least someone was happy,
Not sure if Volvo do the same sort of thing?
It could be the traction control cutting in, was it icy or greasy? or it could be a traction control fault try turning it off I think its ASR on the switch theres a picture of the inside of a FM12 cab on my pics (tony53) you might be able to zoom in
tony
Isn’t ASR the engine brake?
Traction Control is marked TC.
Krankee:
Isn’t ASR the engine brake?Traction Control is marked TC.
Ithought TC lived in Middlesbrough and confused people and ASR was Anti Spin Reduction or something
It could have been the Traction Control cutting in, it is very sensitive on the latest Volvo’s, and sort of stays in action for a second or two after it cuts in. But, you should notice the symbol of it on the computer display, if it was that.
You beat me to it guys, i was thinking about Traction Control causing this before I got down the thread.
The Actross’s I drive have it. If the road was slippy, a lift axle down & the load not heavy, then if he accelerated at all spiritedly away, it would cause exactly as described. Lifting the axle & being steady on the gas pedal until its pulling in higher gears should solve it.
Rgds, Jonathan