engine jumpy in low gear

[anyweb]

hi guys,

now that i've decided to keep my car (for now) I'd like to sort some things out over time, and one things that's bugging me is in low gears (1st/2nd even 3rd sometimes) if i take off the acceleration, then it can get jumpy, almost as if not enough petrol is getting through.

If i leave the car in neutral it revs away at approx 800rpm (i think) and doesnt cut out, however if i slip into first gear and use no accelerator pedal, the car lurches, same if you apply just moderate pressur to the accelerator pedal, it causes the engine to 'jump' which causes your foot to move forward which either ends in an embarrassing abrubt stop or a jumpy 10 or so metres until gear change

it was services (new plugs/oil/filters) at 180,000KM and is now reading 183,000KM, and i've noticed this since it was serviced, so any ideas ??

am I under-revving ?

I forgot to add that in 4th and 5th gear at 90km/h or 120km/h there is absolutely no noticeable under-revving with the accelerator pedal pressed or not.

its a Merc C220 (1995 model)
cheers
anyweb

 

[Myros]

anyweb, even my 280 is subject to the odd

driveline shunt. It doesn't show on autos, as the slushbox dampens out the oscillation.
You just have to adapt to it, and feather the clutch out and gently squeeze the gas, rather than prod it.
As you increase the load on the engine by fading the clutch in, it will try to stay at 800rpm, having sensed a rev drop. the load increase then suddenly vanishes, as the clutch comes home fully, and bingo, the engine recoils past 800rpm, then drops again, and you have a shunt.
Try keeping the revs constant at about 1000rpm and fading the clutch in.

or it could just be the MAf needs a clean, or the accelerator cable needs a greasing.

 

[Myros]

just had another thought

183,000 km and over 10 years old. Maybe the ignition packs are biodegrading. that would also give you a bit of lumpyness at lower engine speeds resulting in a shunt.
I believe an easy test for this is take the ignition lead covers off and run the engine in the dark ( you'll probably have to wait until november for that in Sweden). You should be able to see the leads /packs arcing out onto the engine block/cylinder head.

 

[C220GJS]

I may be wrong but I think the coilpacks on Anywebs car are mounted under the inlet manifold (really convenient), and do not suffer from the problems that plague those with the coil packs on top of the plugs as the wiring is not exposed to such high temperatures.
Geo.

 

[starman65]

SLK 230 1997 Auto gear change problems

My automatic gearbox is jumpy too. I drive along for a while everything ok and then hear some whirling noise under the bonnet ( which i assume is the supercharger) and then it wont chage up. It gets stuck in second and i can't pull away from stationery. To correct it i have to turn the enging off and then on again. Very frustrating.