Engine revs changing up/down when coasting over 80km/h

[vsuterus]

Just wondering if anyone has this same problem - It appears when the torque converter is locked up above 80km/h and you are coasting with no throttle at all the tacho is all over the show, jumps around between about 1300 and 1500rpm. Both my VP and VS calais do it - though the VS does it worse. A prime example is when going 100km/h with the cruise on and then tapping the brake pedal to disengage it and while the speed is dropping the revs are bouncing around - but the car doesnt shake or jurk or anything.

Also the VS does sometimes slow down much faster than it should when coasting, as if its in 3rd gear instead of Drive.

Could the torque converter be on its way out or is this a common problem?

 

[blue alliance]

No think it's just the way it is man. My Vt does it when coasting, Sounds quite nice with a good exhaust.

 

[Harvs82]

I'm pretty sure thats normal, mine does it at 100 km/h coasting. I'm sure I read somewhere that its actually the computer saving fuel by not firing all injectors, or something to that effect.

 

[Blown88u]

When was the last time you changed your ignition leads... 1 of the first signs of lead failure is a spastic tacho. leads are about $50-$80 so swap leads with someone else ( preferably 1 at a time ) If that is the problem then you will be losing power and could be doing damage to your ignition system I have owned a few vp and vr autos but dont recall that happening. Harvs82 has a good point though. Does the engine race when the tacho jumps around ???

 

[TheForgotten]

my vr does it too. sounds unreal wit my exhaust

 

[sheldo86]

Yep, I know exactly what you're talking about. My VR does it, always has, seems like it happen o everyone though.

 

[vsuterus]

Thanks for the help guys. Sounds like it happens to most people. Quite weird really. I'll check the leads anyway, they're only a year old but that doesnt mean anything. I guess it could be a fuel saving mechanism, makes sense.

 

[frenzal_tom]

yeh i think it is for fuel saving
when i use cruise control i head downhill the revs drop and the inst fuel metre says 0ltrs/100km so im guessing its suppose to do it

 

[mwb235]

i've owned my VR since 2000 and it had this same problem from day 1. In 2001 i replaced the leads and injectors (as part of a major service) and the car still had the problem, and has done ever since. Most people i have mentioned this to also say it is normal...

 

[ENNVS]

I also have this problem with my VS it seemed to have gotten worse since i got an exhaust