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Discussion Starter #1
2005 elantra, 90k miles, used to have steady idle. now idle drops (from 750 to 650, and then feels like it hesitates. acts completely normal as soon as you touch the gas), this happens when...., shift from park to any gear, turn on heat or a/c, turn on lights. so far timing belt and water pump changed at 75k miles. tps sensor changed, 4 motor mounts changed, valve cover/ gasket/ spark plugs/ wires/ ignition coil on 9/19, new thermostat, and new IAC valve. basically leaves MAF sensor, which i cleaned at some pt. but could be bad MAF? any other ideas?/common issues im missing? thanks
 

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It's the IAC I bet. If it is like what my Accent has it is a cylindrical barrel type. As it carbons up the barrel will not roll smoothly or stick. The obvious symptom on my Accent was no cold engine fast speed idle.

It is easily removable and cleaned. Only goes back together one way.
 

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I thought it was the IAC also, cleaned it first, made it worse, bought a new aftermarket, didnt help, sent it back and ordered a hyundai oem, deff made it better, but still feathering/ dropping sometimes. annoying.
 

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I dont believe so, there is a idle screw on the TB, but u have to pry off a plastic cover, i raised it a little, it helped, but then with the new iac my check engine light came on for hi idle, so i lowered it a hair.
 

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Discussion Starter #9
tested TPS .49v steady at closed and 4.2v WOT, no dead spots, moves up and down smooth.

checked idle, sits at 750 rpm when warmed up, but feathers to 740 rpm with no accessories running. so a minor fluctuation. once i turn on any electrical acc. (heated mirrors, headlights, heater/ac) it drops down to about 730 rpm, but seems to fluctuate a little more. once i turn off the acc. it goes back to 750 rpm. it doesnt bother me that it drops down, it just annoys me that it is feathering.
 

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You can give the IAC some more head room possibly.

See if you can get it to idle around 500 rpm or lower with the IAC disconnected and the engine warm by adjusting the throttle stop screw if it has one.

Then turn off the engine, disconnect the battery and reconnect the IAC. Hook the battery back up and cycle the key a couple of times with out starting.
 

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Discussion Starter #11
Update. Thanks Red Raspberry. I reset the idle screw, after unplugging IAC it went to 1600 rpm, but even taking the idle screw all the way out it only went down to 1200 rpm. Then I unhooked positive cable and took out the ECU fuse. After a few minutes hooked it all up, cycled the key to on position a few times and started the car. Immediatedly went to 750 rpm, I let it idle like that for 10 minutes. There was no feathering, idle was steady. Took it for a 35 mile drive ran great. No more feathering and when I turn on an acc. it might drop a hair, but if it does it goes back up to a steady idle. Most of the time it does not even drop the idle now, it actually goes up a hair to handle the load.

I have unhooked the battery before and reset it, but it never changed anything. Again thanks!

I had another post because it would not shift out of third when going uphill, did not matter if you let off or gave it gas, it would stay in third untill you topped the hill and leveled out. Then it would shift into 4th no prob. After the reset it shifts normally again.
 

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It's good to hear. With the new electronic throttles there is little you can do but clean and change out. The older stuff still responds to mechanical changes. I use to slot the TPS sensors on Fords so you got more adjustment.
 
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