Here's another interesting observation.

The car idles "free-er" when I start the car in neutral and depress the clutch. Revs at around 1400 rpms Once I leave the clutch while in neutral, the idle seems tighter and it drops instantly to the 1100-1200 rpm level.

Then, the above happens. I'm not sure if this means anything

 

Try changing the PCV too, when that gets clogged lots of weird stuff can happen to the idle.

 

My car also idles free-er with the clutch in. I'm assuming that is normal. Also, if you put your lights on, i bet it will idle lower again.

 

PCV valve is brand new. Full maintainance done.

 

mine does the exact same thing, has for years. its allways bothered me, and i never could figure out why it does it it. ive replaced my TPS, ecu, PCV valve. and quite a bit more, and it still does it.

ive come to the conclusion i think its just a weak alternator. maybe ill toss a OHM meter on it, and see what kind of juice im getting on start up.

 

Hey, this is also happening to me now. I have an auto and if the car's at idle and I lay my foot on the gas pedal and just let the weight of my foot start to push it and then push just a tiny bit more to actually move the pedal the rpm's drop and it gets to a close to stalling feeling for only like half a second and then will continue to rev up...I don't know what the problem is. I think I'm going to buy some new plugs and wires just for the hell of it (wanted them for a bit anyways and it might help this problem) and see if that help's. I just don't like it happening...I never want a car to feel like it's going to stall in the middle of an intersection.

 

^^ that happens to me to^^

if i hit the gas just a bit, but quickly; the rpm will drop for a sec then rise normally...
i think it might run too rich just as u hit the gas, it doesnt need much at low rpm... so it sputters while it clears the cylinders then runs fine.

ive had a bit of oil in my intake to so that might have somthing to do with slow responce on the tps...

ive got a stick BTW

 

Ok, here's the deal. It's really hard to tell what the engine's doing without the use of an ob2 scan tool that visually displays live datastream. However, with a little know-how, one can determine the cause of the problem (not as quickly, mind you) without it.

First, eliminate all the maintenance. PCV is done, which *could* have an affect on it's running condition, but doubted. Plugs, wires, etc.
Eliminate vacuum leaks. Sometimes, a cracked hose or leaky gasket (even the one at the tps) could be the cause. When the engine heats up, vacuum leaks sometimes go away. To test for these, use a plumber's propane torch, and turn it on just a little. Don't light it, we only want to use it for the gas. Move the torch around the engine while it's running and listen to the way it runs. If it idles higher, or runs smoother with the nozzle in one area, that means that there's a vacuum leak nearby, and propane's getting sucked in the engine. Don't be a dork and shoot propane into the air filter and think that's where the problem is... please....

Next, the more likely culprit is the tps. There's a tsb on it from hyundai. Says you should (with the engine running and all loads off) use your finger to press on the tps wiring connector with enough force to deflect it towards the back of the car. If the idle changes, replace the tps.

I, however, would use a multimeter to check for voltage at the tps. With the engine off, but key in the run position, check voltage between the white/black and green/white wires for 5.0 volts (+or- .5v) Then, check between the white and green/white wires. It should range between .5 and 4.5 volts. Open the throttle slowly and watch the voltage change. It should change smoothly without any dropouts to 0 or 5 volts.

report back

 

Honestly I think this "problem" is more normal than a problem. It takes the ecu a split second to see that u tapped the gas suddenly and it doesnt give it more fuel until it sees that change and tells the injectors to ope up the pulse width a little more. 5 tiburons now, all with kefico tps have had the same thing.

BTW, holy dead topic. Almost a year

 

^^lol, I was thinking screwdriver sold his tib.