It all happened yesterday...
It was a damn hot day (around 32~34 deg. cel.) and pretty humid.
I was on the way back from work, and got on to straight road. My A/C was blasting cold air all over the place since it was boiling in the car. My audio had five bars indicating volume level.
I maintained 60km/h~62km/h and all of the sudden, while I was on the gas maintaining the speed, as if the gas was cut off, rpm would drop to 1000 rpm then back to 1700 then back down to 1000 then back up to 1600 within 1 to 2 seconds. It sounded so clear that something was wrong. Then I stopped at redlight almost blanked out due to what happened. Then Green light, I put gas, it was fine. Then before next light, again! but this one was more mild dropping from 1700 rpm to 1500 rpm, back up then drop and up again.
At that point I was like "WTF happened to my car?"
Then, I got onto highway 401, I didn't feel anything wierd after that.
Then again, after I picked my sister up, I wanted to check if everything was okay. On the road infront of my house, I slowed down and maintained around 5 km/h to 10 km/h. And I felt really unstable output from the engine. As if the car was hasitating to accelerate/move. It was like move, move, less output, move, less output,.... etc. It sounded like engine was struggling to maintain speed of 5 km/h. I felt it more when the engine is reving low. Mostly around 1000 to 1800 RPM..
Then today, I didn't feel it at all. Even on pretty low rpm.

Damn, what the hell is this? Could it be the battery? I haven't changed the battery since I got the car in June 03. My car has 67000 KM, and I always put Sunoco 94 octane until recently I switched to shell 91 v-power (I think I put around 5 tanks of v-power fuel already).

Any suggestions? Oh boy... Im gonna go crazy..

 

it is probably IAC Valve about to give up.

 

IAC valve? how much to fix? any other suggestions...?

 

The "I" in IACV stands for "idle" -- as in it has nothing to do with the incoming air when the engine is not idling.

Honestly, it kind of sounds like a torque converter problem. It could be failing to lock and unlock, and at around 60 KPH, it sounds about right. On these cars, it's normal to feel the torque converter lock and unlock at those speeds, but I have experienced something that sounds like what you're describing. It happened in my car once and scared the crap out of me. But then it went away and never ever happened again.

So it could be a fluke, in which case you don't have to really worry about it. But keep an eye on it, and if it happens again, take it in for service. I would imagine that it's a torque converter problem, but not for certain.

Your check engine light isn't on, is it? Just curious, because if it's a transmission/torque converter-related problem, you could get a failure code.

 

The light isn't on... Oh boy, I guess all I could do is cross my fingers and hope that it was a fluke!

 

uh. when i was installing my cai. my cuzzin forgot to plug one of the idle plugs into the throttlebody. and when i started the engine, it started up but it was strugglin. so maybe one of ur plugs are loose.

 

I will check the plugs!

 

would heat contribute to this? yesterday was pretty damn hot here..

 

Yeah I thought of it too. The A/C was constantly on. It was blasting all over the place as I wrote.. Maybe the heat contributed?