RPM question
 

hi everyone, here's a question for ya:

i have a 2003 P5 AT with 2500km on it. when i'm going about 80kph and i let my foot off the gas, the rpm decreases for a bit, then it goes back up (approx. 500 ish more), then it drops again, and goes back up a bit. all this time, my foot is off the gas. so in other words, it fluctuates 4 times before it becomes steady. During this, I do not feel any abnormal things happening (like tranny jerks or engine sounds rough). Everything feels normal. Due to my lack of mechanical experience, I don't know if this is normal for the tachometer to fluctuate like this. Of course this is my first car with a tach.

If anyone can answer this question would be greatly appreciated. I don't want to ask the mechanics at my dealer, cuz everyone knows what they'll say "it's normal for this car".

Thanks

It sounds like the torque converter is trying to decide whether or not to lock up; the rpm fluctuation is caused by the converter repeatedly engaging and disengaging. I don't own an automatic, so I can't comment on whether or not this is normal, but I can't imagine that it would be harmful.

I have an automatic too.........and exactly what buddy said above is it!
 

:withstupi


I have an automatic too.........and exactly what buddy said above is it.

hey thanks Chris for answering my question, and thanks chuck for confirming it.

but chuck, does it happen in your AT P5 as well?

Yep ...........I really noticed this because I had my car since May 2001
 

Yep ...........I really noticed this because I had my car since May 2001

I have AT as well and it does the same thing. Perhaps the computer always applies a bit gas every time it changes gears.

I have noticed one other wierd thing to my AT p5. I accelerate to around 100 Km/h (65.9 mph) then I set the cruise control to on.

At this speed the RPM meter is showing around or close to 2800RPM. Then I start tapping the resume button once every other second. This will increment the speed by 1.5 km/h.

Then I notice the RPM (tachometer) goes to 4000/RPM and stays there for about 5 seconds and goes down to normal around 3000/RPM (little bit more than 3000). It does this and I am sure that the road is straight and is not going up or down the hill.
It only does this in cruise mode.

Any idea if this is normal or something I should be worried about.

Manado_P5

Stop trying to confuse the cruise control computer and maybe that won't happen. :p