PCM Upgrade affecting RPMs?

[crash1977]

Hi Guys,

I brought my 2002 P5 in for servicing on a suspension issue. While the dealer was working on it he said he heard a noise from the engine and would be upgrading the computer onboard which he said would fix the noise.

I assumed he was going to perform the cold engine fix which I heard about but I don't think he did because he didn't replace the VTCS valve he just upgrade the software. Also the cold engine rattle is still there.

However I now notice that my car revs about 300RPM less then before. When I used to cruise at 100 KM/h I would rev at 3000 RPM, now I rev at 2700. When I used to do 120 KM I was just under 3500 RPM, now I am at about 3200.

Has anyone else noticed this? I thought RPM were fixed to the speed and should not be affected by software.

Thanks.

 

[Kansei]

Do you have an automatic?

Unless he replaced ur tranny this wouldn't really happen with a manual.

 

[crash1977]

Do you have an automatic?

Unless he replaced ur tranny this wouldn't really happen with a manual.

Yes, I have an Automatic.

 

[jblon78]

Even with an automatic i dont see how your cruising rpms would be affected. The 300 rpm difference kind of sounds like the torque converter wasnt locking and now is. I know on my car 70mph is just a bit over 3000rpm. Until your car is warmed up the car will not go into overdrive once it does it is roughly a 300 rpm difference.

 

[crash1977]

Even with an automatic i dont see how your cruising rpms would be affected. The 300 rpm difference kind of sounds like the torque converter wasnt locking and now is. I know on my car 70mph is just a bit over 3000rpm. Until your car is warmed up the car will not go into overdrive once it does it is roughly a 300 rpm difference.

I am certain the car was going into overdrive before... when it would kick in it was more like a 500RPM drop.

I am positive that now the car is revving slightly lower and the only thing that was done was an upgrade to the PCM (or so the dealer says).

Is it possible that when the programmed the new PCM the computer somehow thinks I have a different size tire and so my speedometer is reading a certain speed but in fact I'm going slower which is why my tachometer is showing less RPM?

 

[Kansei]

Oh I forgot all about the speedo being electronic.. hmm

BTW welcome to the forums!