car idle goes up and down and bogging out at 5ooo rpm

[gxser]

ok i have a 1.6 doch and just swap another 1.6 in.... idle is rough and when i give it hard throttle around 5000rpm it will bog like i would be hitting the brakes.. rpm gauge just goes eratic and cheq engine goes on.. i ease off the throttle it pures like a kitten doing 110k on highway.. i was just wondering if this happen to someone and had answers to this thanks

[reedw75]

I got a similar problem (95 mx3), just swapped another 1.6dohc from a 94, fairly certain i got bad injectors that are leaking down under excessive load

[wytbishop]

80% of the time that would be an ignition problem. 18% of the time that is an unmetered intake air problem. 1.8% of the time that would be bad timing.

0.2% of the time that would be a fuel injector issue.

Take your car into a dark garage and watch the spark plug boots as someone revs the engine up slowly...you will see arcing between the boots and the head if there's a bad boot or two...which there probably is. You are losing power because the spark is leaking to the head at high RPM and not all of your cylinders are firing. Could also be a failing distributor.

[gxser]

found the problem !! it was some kind of ground nut around the thermostat hahaha