you sure your CAI isn't hitting your battery? i've had that happen to me and the same thing happened with my idle.

 

Yeah, there's clearance... what would that do?

 

Pulling the vacuum line off the regulator bumps the fuel pressure and enrichens your mixture. The closed-loop system may or may not have been active.

An engine "prefers" mixtures of 12.5-14.0. However, this is not good for economy, so we set the AFR at more like 14.7.

If you enrich the mixture and the problem got a TON better, then that points to lean AFRs, and a very common cause of this is vacuum leaks. Do the first thing I posted about checking the intake. If you can't pressure test it, then fire the car up and listen for leaks using a stethoscope around all fittings, lines and air hoses. Report back.

 

A short like that would cause an idle drop, stalling. It happened to me. I think a wire may be touching something metal, or something isnt grounded. I doubt it since you do great work, but its all i can relate to.

Poor you, must have scavaged through the entire car.

 

A short wouldn't change behavior as the car's fuel pressure changed. I'm still going with intake leak.

 

I changed out my IAC and the car feels alot better now. It almost feels like the gas pedal is heavier and works harder.... It's odd to describe. Also, the idle is more floaty. I don't want to call this problem fixed, but it feels better for now.

Check out this video of my vehicle coasting with clutch disengauged and RPM bouncing up and down at 30mph


It's not doing that anymore, but that was somewhat intermittant.

Maybe I had a deadspot in my IAC?!?

 

It shouldn't bounce like that. Is it quietly popping out the exhaust as it bounces?

If you have a Beta 1, that has a 3-wire, 2-position valve that is operated using a PWM signal. If you have a 5- or 6-wire IAC, then it's a stepper motor. PWM valves don't have "dead spots", where as stepper motors might if you have one bad coil.

 

dtn you know more about this than i do so i can't help much, but i'd say it's a power issue. i wouldn't expect any hyundai to do that out of the blue, especially one from 2000. my friends fam has 3 tiburons, my family has been through 3 tiburons, 2 excels, and 2 elantras, and i've never seen this problem.

i'd say it's your coilpack, or as Enthalpy suggested one of the coils is burnt. check your spark plug wires to see their condition. there is a way of checking to see their status, i just don't know it. my opinion is it's electrical and not mechanical.

wish i could help more...

 

I took apart the IAC which was on my car and found some buildup on the contacts/brushes. It was black in color. Upon reassembly I found that the resistance dropped to within tollerance.

Hyundai specifies a close tollerance resistance value on the IAC for a reason!

Here's some pix.

In this picture, at the top, you can see the black buildup I was talking about


In this picture, you can see an adjustment of some sort for the IAC spring. It's the brass thing at the bottom of the IAC mounted to the aluminum. It can slide back and forth with some pressure. It actually sets the stopping position for the IAC valve. Any ideas on the proper setting?


I believe this problem was caused by buildup on the IAC contacts. Some buildup could be to blame if it were causing intermittant contact at just the right place

I need some kind of a press or a big pair of plyers and a tool to press in the edges so that it stays together. I'd say a repair on this part is feasable as long as you have a strong tool to bend the pressed fittings back into their proper location and you reassemble it correctly.


There is a check, you can check the high side and the low side with a ohm meter. They were both good. I really think this problem is solved. It was a PITA to fix, had me tearing out my hair and spending money like mad on common replacement items. The IAC is very touchy on our cars.

After seeing the condition of my IAC, cleaning it and having it return to normal values, I'd say the problem is fixed.

-intermittant bouncing idle
-intermittant no idle up
-inability to control idle consistantly
-Idle sometimes unstable
-idle sometimes too low
-idle sometimes too high
-idle sometimes dips
-idle always falls too fast

Buildup on the IAC contacts could cause all of it.

I replaced mine, but the next guy could clean his.

 

wow... that's crazy, just check back in to tell us everything is all good. good fix and good luck!