Hi Everyone, was wondering if anyone can help me on this problem.
Have a Mazda 626 1989 Auto.

When I have the car in Park/Neutral the rpm is around 700-800.
But when I put the car in Drive, it drops to 600 (I think it was the same before this problem)
and press the gas(Accelerate) from a stop, the car hesitates(jerking).
I notice the rpm will go up to 1000 and drop and back up until it stablizes. It then drives fine onwards.

Also, if I press the gas pedal slowly from stop, I don't get the hesitation. It will drive and idle fine.
It feels as though some sensor is not providing the correct information to ECU and therefore it is trying its best
to adjust when I hit the pedal. There is no check engine light.

Thank you.

 

In case anyone wanted to know the solution. As expected, it was small crack in the
intake boot. Somehow I missed this.
Thx.

 

Good deal, maybe this will help someone.