Change Engine

[Naeif]

Can anyone help me what’s happening to my pathfinder because I change my pathfinder 2005 model to 2004 model engine and now im suffering from low speed. Is it need to modify something like ecu?

[Slartibartfast]

Low speed could mean a lot of things. I would pull codes first, see if the computer can tell you what it's upset about. Could be something didn't get plugged back in. Could be the new engine's throttle body is slightly different from the old one, and the computer was alarmed by the sudden change, and now it thinks the throttle's broken and it's running in limp mode.

 

I don't know which engine you're working with, or when model changes happened in your market. I'm assuming this is a like-for-like replacement rather than some crazy swap. I have read that the early VQs are pretty picky about which year you can use for replacements due to design changes.

[hawairish]

On 10/12/2024 at 1:51 AM, Naeif said:

Can anyone help me what’s happening to my pathfinder because I change my pathfinder 2005 model to 2004 model engine and now im suffering from low speed. Is it need to modify something like ecu?

I'm presuming 2004 R51s existed in Qatar, and that we're talking the same engine between 2004 and 2005, being the 4.0L VQ40DE, correct?  If yes, then probably not the ECU beyond potentially a learning process required for the throttle as Slartibartfast suggested.  You'd need to pull any codes with a proper scanner...one that can also pull chassis and transmission codes, not just OBDII (or whatever the standard is in Qatar).