316ti auto 2003 N42 issues -hesitancy/juddery at low revs

[StefanAnghel]

Hi zoners,

I've got this 316ti for London roads (e30 is too low)
Automatic 2002 (52 plate) 71200 miles, full service history...
New spark plugs and ignition coils, oil and filter, some gaskets
Cleaned the vanos solenoids and replaced the gaskets

When cold the car runs smooth but as soon as it's warm there is this hesitation/juddery when accelerating from stand still up to 2500-3000 rpm.

Funny enough if I disconnect the vanos solenoids and plug them back (the idle goes up and down a bit) the engine runs as it should... nice smooth acceleration until I switch it off again (I presume it's running on limp mode-due to vanos solenoid disconection)

Any ideas would be much appreciated - must be an electrical issue/sensor

Thanks[/u]

[darkchild]

They love a crank sensor but that normally results in a complete lack of go. Definitely a job to pay someone else to do - it's horrible.

My old 318ci had a faulty coil pack that resulted in juddering but you've already replaced them. It was really bad at idle from what I recall.

The N42 is just a horrid, horrid thing.

[StefanAnghel]

I have always stayed away from 4 cylinders...now i'm trying to get it fixed so I'm not defeated by a silly engine...
The idle is fine.. just the acceleration from stand still... and not on limp mode
First I thought it's an air leak, then the vanos solenoids but it's strange that on limp mode it's fine..

[wellard]

When the engine goes into limp mode it switches off the valvetronic and uses the throttle body to control the air into the engine instead of the valves. Try disconnecting the air mass meter and driving it,this will switch off the valvetronic system as well. If it drives better then the problem lies in the valvetronic side or maybe the air mass meter itself.
Also check the breather system, lots of brittle plastic pipes under the intake manifold causing air leaks.

[StefanAnghel]

I'll try that and reply
Thanks

[StefanAnghel]

Disconnected the air mass meter and after few up and down revs all went back to normal... a light on the dash board but the acceleration was smooth. Connected the air mass meter back, swiched it off and back on and the light was gone but the problem was back

[Andyboy]

Air mass meter. I may even have one. You need to read any fault codes - could be the valvetronic sensor, a lovely job to replace.