RPM Dips
 

So this has been happening for the past week or so,

The car idles fine at ~600-700 rpm and when I apply gas it goes up fine, the only problem is that when the car is moving and I do not apply gas, the rpm goes from around 1200-1500 down to 500-600 then back up to normal in about a second. There is a noticeable slow down when it does this.

Spark plugs were just changed,

I just bought this car 2 months ago second hand, has 103 XXX kms on it.

All fluids seem to be fine.

Any help would be nice

this is also happening to me. even my mechanic/handyman cant figure it out.

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Sounds like a bad throttle position sensor you can check it with a dmm if you know what your doing the best thing to use is a lab scope

First thing I would do is get throttle body cleaner and maf cleaner. Always start with the cheapest methods :D. Its common on our cars that the throttle body can get gummed up and since the IAC motor is right there this can cause a momentary dip in idle when coming to a stop as the IAC cannot compensate fast enough once the rpms drop initially.

I just posted in another part of this forum regarding my car with similar problem as yours, I've attached a 15 second video to this post...

https://www.evolutionm.net/forums/la...ng-glitch.html

Can you please verify that my problem is the same as yours? if so, could you please please please update me if you solve your problem?

Thanking you in advance.

Bobak.

Hey, no that seems like a different problem, my car idles fine. The problem is when I am traveling at speed and dont apply gas, mostly on turns, then it dips and the dip is greater than yours more in the 300-400 rpm region. I'm going to try some seafoam to see if that cleans out some stuff when i have the time.

Check the coil cables to the spark plug. One of the rubber plugs could be arching (grounding out) against the head cover. This happened to me and once I replaced them, it didnt "dip" at all. just pull the caps to the spark plugs and inspect for any white markings outisde and inside the cap. If there is white markings then there is your problem. But this is just one solution, Im just giving ideas of what it could be. Sometimes its the simplest thing that will throw everything off. Hope his helps

I had the same problem on my foxbody mustang. it was a bad throttle position sensor. you should be able to use a multimeter and check the voltage on the sensor to make sure it is working properly.