I have a 2004 5AT with 3500miles on it... If I am in 1st or 2nd gear and let the RPMs biuld slowly, not flooring it or anything just shifting later in Manual Mode as the needle passes 4000 the car seems to get rough and then smooth out. Its only lasts as the needle passes the 4K mark so it's not even a second long, its very fast, but noticeable. Whats up with this? Should I be worried? I have never noticed it before and I 've had the car for around 3 months.

The only other ways I can describe this feeling at 4K is a hesitation, or like the car hits a bump....

Also, if I do floor it the shifts are smooth and crip and everything is smooth throughout the entire powerband....Thanks in advance!

 

Just a thought, Maybe O2 sensor needs checking? Either way, that's what the warranty is for......GL2U....Dave

 

I did put the AEM intake on about 3 weeks ago....I'll check, any other ideas? I have to take my cars 4 hours to get it checked out...will a nissan place in town be able to do it?

 

mine does it too (03, 16K miles). only if I've been messing around in MM mode. that tells me its an ECU/TCM thing. Lots of other people have mentioned the same thing. Its odd, but I dont think its anything mechanical to worry about.

 

I dont have this problem when in MM. But it does get louder and deeper pass 4k rpm which is good

 

sorry ...but what is MM mode?

 

i think MM mode is when u put the shifter into the manual shift thing, manumatic mode... in the auto when u control the shifts...

 

Thats your "VTEC". Or is it called vvtc or something like that.

 

Building on what he said^^

At 4000 rpm the ECU resets the Air/Fuel maps to be more agressive and more responsive. i noticed on the dyno charts mostly. I also notice this everyday whenever i drive in A/T or MM it still happens. Its sorta like Honda's V-TEC or Toyota i-VVT.