New here, not so much to cars. This one has been giving us a problem from about 80k, it has 90k on it now. Made a post on another mazda forum and got no response.

The car is a 99 626 2l DOHC. Whats happening is at idle in neutral or drive occasionally the car will sputter and stall it's self. It corrects it'self and is fine in drive. It will also throw a check engine light and the OBD port reads a "system too lean". So i've replaced the obvious, plugs, wires, properly gapped etc... I've also replaced the fuel filter for regular maint. and the bank 1 o2.

I have heard the intake manifold gasket is a common problem, however we're not losing coolant that i've noticed. If this is the case the car might just be getting pawned off, I dont feel like putting the labor in it. However I know the IAC could also be it, but when I unplugged it at idle it stalls the car. I thought when the IAC goes bad you wouldn't notice a difference unplugged. However being such a sporatic problem how could you tell?

Thoughts, opinions?

 

Shall I post my rides?


This is a project truck I paid 200 dollars for, I think my total build cost is like 450-500 now



I built a focus awhile back, kinda fun but needs some love.

Heres our mustang we got a few years back, was in great shape but was a bit neglected. Brought it back a little.
Heres a before motor pic






and the focus, built it from stock as well

 

Have you looked for obvious, or not so obvious vacuum leaks that may not affect the idle when in gear? e.g. Idle control solenoid compensates for.
Of course the std test for intake manifold or other vacuum leaks is starting fluid spray into the suspected area of the leak while the vehicle is running.