Have a high idle sometimes (either in neutral or with clutch pushed in)

Car drives fine, just idles annoyingly high. Sometimes about 2k sometimes about 1500. Also if you hit the throttle while stopped it will rev up and then VERY slowly come back down.

Anyways, tried starting it up with the TPS unplugged, and it idled just fine. Left the car running and plugged the TPS back up, and the RPM's jumped up instantly.

Could this signify a bad TPS, or could it be simply bad connection? Or something else entirely?

Thanks for feedback.

 

I'll guess a leak in your PCV system... are there any cracks in the lines or rubber connectors especially around the back of the engine valvecover to valvecover? Is the groundstrap boot thingy that houses the PCV valve loose or torn? Is your TB blade boogered up with oil or dirt and not closing all the way? Is the coupler from the TB to the MAF loose or leaking? Could be your TPS, but check for an unmetered vacuum leak (post maf) before you spend any money on parts.

 

Try cleaning your MAF?

 

Would those explain why it idled fine with TPS unplugged but not when I plugged it in?

 

Bump! Mine is doing the same thing and I've had no luck fixing it

 

Kinda sounds like a vaccuum leak. Easiest way to find it is with a can of starter fluid.

 

Did it just start doing this? After you installed the cam and had it tuned, did it return to idle slowly then or is this new too?

 

check your iac

 

OP...when you push in your clutch to come to a stop and your car idles up...if you let it go back down to normal idle rpm's before taking off, does the car still idle funny? Or does it clear up and drive like normal? I'm having very similar problems with my car, but if I let it idle down on it's own to 750-800 rpm's, and then take off, my car drives perfect. It's like it's "self-tuning" itself.

 

I will shed some more light on the OP's post since I just sold him the car . It is not a vacuum leak. I had looked everywhere and couldn't find any leaks. After the car was tuned it ran fine. Started and idled just fine as well. It started doing it shortly after I got the tune. On a cold start the car idles normal, the rpms drop like normal and there is no hanging idle. After the car warms up it starts to hang a bit but will still come back down at a complete stop. After you shut the car off and restart it the rpms will shoot up to 2k or so and sometimes drop back down, and other times it will sit at 1500 or so and not drop.

I hooked up a scanner to the car and the TPS was reading 11% with the car off. I could hit the gas and let off and it would read something else. The TB blade closes all the way as well so that's not the issue. I think the TPS is bad.

 

Does the problem exist while driving/after moving the car or is it only just after a start?

If it happened right after the tune, no doubt the tuner messed with the TB/IAC screw and/or messed with Base Running Airflow. If there are no mechanical problems, this is what I would examine. If a sensor was bad, a CEL should indicate it.

 

swapped the tps out and it still idles high

 

OP...I tried switching my TPS out too and it did no good. I just ordered the TPS pigtail in hopes that would fix it. I'll let you know what happens

 

its probably a problem in the tune.. most likely in the Throttle follower or throttle cracker tables...
it could also be as simple as the IAC table has been screwed with and it needs to be set back to stock values

it could be that the Throttle bump stop has been used to open the blade to get air for idle, and its been moved too far...
you can check for TPS voltage with any scan tool that reads OBD2
if its above 0.55volts, then its too far and it can also cause it to do what you are describing.

 

Thanks for the reply Andy

Put in a new TPS, but it didn't fix it

Took out the idle air valve and it was kind of dirty, so I'm going to try to clean that out soon

Did you ever adjust the stop plate on the TB?

 

Joe, it seems to take a a couple of seconds of being stopped for the idle to drop down to normal everytime. It's bit too bad most of the time though. Have only had the car a couple of days so still haven't seen how it always acts. Lemme know if those pigtails help you any

And soundengineer, would there be any way to tell if one of those tables needs adjusted, or would I just need to go for a new tune? Checking the voltage seems like the easiest/cheapest thing I can do first

 

check your tps voltage and as he stated, throttle follower and idle airflow (base running) may need to be addressed.

 

Have you tried the tps reset?

 

Just go to an Advance Auto and hook up their scanner and watch the TPS meter while your car is running. I did that to mine last night, and the scanner was showing my TPS was stuck and .3% and when I'd idle up it would drop to 0%. Since I already tried the actual sensor, the pigtail is the next logical try. Worth a shot with yours too since you've already tried the TPS

 

Right here is your issue...

it needs to read 0 or 0.4 with a flicker at 0.8 at the most
at 11% you will always be in the throttle follower table...which adds air, which causes high idle.

get the TPS back down to 0 and your problems will go away most likely
if the TB bump stop screw has been used to open the blade for idle air, then you need to test the voltage, again.. MUST BE LESS THAN 0.55volts
if you cant get it to idle with the voltage below the 0.55, then it needs more air and you have to drill a hole in the TB Blade

once you get the Voltage down, you must do a TPS reset
unplug TPS, turn key on for 10 seconds, turn off key, plug back in sensor, turn key on 10 seconds, turn key off, start the car.