Mazda 3 hatchback shaking problem

[Ant]

hi eric . i got a question for u . i have a 2004 mazda 3 hatchback and im currently in school for auto tech. i noticed whenever im in gear at a redlight or stopped in gear my rpm will jump low and i get a big vibration but when i put it in neutral or park it goes away and my rpm will jump up. I had my teacher looked at it and he cant figure out whats wrong . We tried looking for a misfire in each cylinder and its all fine. I was thinking maybe i got a bad motor mount but there is something causing my idle to drop. There is no vacuum leaks and my teacher said it might be because of the variable valve timing . there is a knocking sound and it seems like its coming out of my intake manifold . Just wondering if u had any suggestions on what i could do to figure this problem out. If there is any diagnosis i could perform.. Thanks Eric

Topic

[college man]

here are some videos to help.do you have a check engine light on?
if so post codes.

[EricTheCarGuy]

Idle problems are often mixture problems. Looking for vacuum leaks was a good start but is the idle RPM where it’s suppose to be? If not you may need to raise it up. Look to the motor mounts last, see what you can do to solve the engine performance issue first. Motor mounts would only be a band aid if the problem is really how the engine is running. Also don’t forget about your tune up items, if they’re old you might want to change them.

[Mike]

I would recommend following the posted video about the throttle body cleaning. I know on Mazdas the throttle body gets gunked up, and the grounds for the throttle body get corroded as well. Source- I’m a Mazda apprentice lol.

[Ant]

cleaned the throttle plates . Havent check the grounds, thanks for the tip

[EricTheCarGuy]

Keep us posted.

[Ant]

hi eric thanks for the info.. still havent found the source of my idle problem but my car drives great besides the at stop idle drop. Would like to see a vid of some variable valve timing if u get one available and the functions of how it works .. Thanks for all the vids . I watch one at least one a day.. Keep up the good work and have u ever thought of a tv show perhaps lol. Stay DIIRty

[EricTheCarGuy]

[quote=”AK” post=37125]hi eric thanks for the info.. still havent found the source of my idle problem but my car drives great besides the at stop idle drop. Would like to see a vid of some variable valve timing if u get one available and the functions of how it works .. Thanks for all the vids . I watch one at least one a day.. Keep up the good work and have u ever thought of a tv show perhaps lol. Stay DIIRty[/quote]

[Ant]

hey eric. well i started cleaning my battery cables and connection to the terminals and my idle now is better when im in gear its not dropping like it was but i got another problem lol . whenever i come to a stop or when my rpm drops to 1000 the needle jumps up and down and it starts driving itself like its possessed.It all started after i cleaned my battery terminals and connectors. I double checked to see if all is put together correctly.Everything is in place. I need some advice and i want to know if there is something that could be triggering that . Thanks

[mckrishes]

I would check the idle air control valve. Maybe it needs to be cleaned if you haven’t already.

[EricTheCarGuy]

You might try tapping on the idle air control valve to see if the idle changes in some way, if it does you might have a bad IAC.

[Author]

Replies