Hello,

My parents replaced there 2003 Mazda 6 for a new 2025 Mazda CX5. I have taken the old car and am trying to get ready to sell. I havnt worked on a car for a long time so thought it might be a good challenge and something to do. The issue is that it has a idle issue. I have been looking at alot of posts but most people's idle issues seem to be pretty drastic with 500-1000 rpm fluctuations. The issie i have is the car obviously has rough idle and when in reverse or drive it will lunge forward or back and not roll smoothly. I put my hand over exhaust pipe and could feel surges of exhaust coming out. Not sure what this means. Only other visible issue I can see is a slight wobble on pully idler. A mechanic was unable to fix this issue earlier in the year. He replaced MAF and EGR i believe. I have cleaned out the throttle body that was quite dirty.
I'll attach two videos.bits hard hear though and much more obvious in person. Any help would be great. I have heard tensioner for serpentine can start to fail. Any chance this could cause symptoms I have?
thanks,

 

sounds iike its hunting but the tach is stable? Check vacuum with a gauge for a steady 18+ inches and then IAC for a smooth motion. Its built into the electronic throttle, you can pop the side off and inspect the gears IIRC.

 

Welcome to the forum

 

To many randomly guessed as the fault parts replace>>>>>>>>>>>>>>>>>
This makes it harder to diagnose because now a experienced person needs to back track and test all the replaced parts first.


Or if they are lucky find the issue or at least narrow it down a bit *by:


The first thing should have done a *complete comprehensive Diagnostic scan.