3.4 high idle (SOLVED)

So I have a high idle but it's 50 percent of the time.
One days it's a t 1200rpm all day and another day it's at 800rpms
I cleaned the air flow meter and throttle body, no difference
What would cause it to run fine one day and another day run at 1200rpms

 

Supercharged and have 545K miles? Hmmm.... Maybe the IACV needs to be looked at. Being sporatic like that it's very hard to pin-point. With that many miles shoot... Could be worse!

 

Yea, I had this problem before at 350,000 miles and it was high idle all the time and was the IACV,
But wanted to see if anyone had the same issues that points me in the right direction before replacing the IACV or the high idle sensor or both while the throttle body is off if that's the problem

 

Mine is doing the same thing right now but I can push down on the throttle body lever arm and it will idle down until I️ give it throttle again. I have cleaned it but it’s like my butterfly is not closing all the way on mine

 

@mechanicjon
@Glamisman

 

Does you throttle body have the little vacuum dashpot that slows the throttle closing or kicks it up?

 

Yup, 3 days ago it was idling at 1300 rpms all day,
Last 2 days it's back down to 900 rpms
I did have a p0120, that i cleared and has not come back

 

Mine has that too. I didn’t know what it was for. Is that our problem!

 

Could be sticking

 

Not to detract from thread, but I love that white sticker with red lettering towards front of engine bay

 

It's brushed aluminum with laser cut in letters and painted red in the letter cutouts.

 

the issue is more than likely a worn throttle body... there are numerous posts on here about that and the one I am thinking of is where the owner sent his TB out to have it rebored, pretty reasonable too compared to a factory replacement.

 

Even awesomer

 

Great point, especially at that mileage.

 

I checked the pod, no it's not holding up the linkage.
I did decide to just toss in a newthrottle position sensor for 50.00 and the rpms went up to 1300 rpms from 900 on this day. I did play around with oiling the linkage and was able to adjust the nut to get it to 700 rpms with the new
throttle body sensor.

Will see what happens this week

 

Well I'm thinking the High idle was a defective throttle position sensor and that's all. Working
part of the time.
Engine is idling smoothly at 700rpms holding steady after installing a new sensor
and oiling the throttle body linkage and adjusting the idle stop screw.

 

Well a month later the idle is perfect at 750 rpms.
The throttle position sensor was the problem.
All fixed, thanks

 

Throttle position sensor goes bad constantly about 90k each. Trick to troubleshooting take out sensor put ohmmeter on pin 1 and 3 should test like conventional potentiometer 1-20 ohms and increase linearly to 5k as you turn it fully. Caught my last one bought from autozone 150 ohms on the low end causing high idle around 1100rpm. Spent 60 this time on awd

 

Throttle plate position in degrees as reported by the TPS can also be read on a good scanner.
At idle on the 3.4 it should read from 9-11 with 10 being optimum. Mine has read 9 since birth, unchanged for 250K miles. Having a baseline number when things are running right is handy for future diagnostics.

Adjusting the throttle stop screw should be for establishing the actual physical "closed" angle of the throttle plate only, not idle speed. The TPS should read the same as actual, give or take a degree at the stop. That's with dashpot retracted/not sticking and throttle opener held closed by vacuum (engine running) or by hand (engine off, ign on).

Some years the TPS can be calibrated a few degrees to match the actual. If the TPS mount screws are in slots it needs to be calibrated, if there are just holes then no calibration is needed/possible.

 

So I just had an issue after changing the whole throttle body unit:

1. Pulled the throttle body to clean the IAC. In doing so, I discovered that the waterway in the throttle body and the IAC was absolutely blocked with brown crud. I cleaned it out and in doing so, I broke the lip off the IAC gasket seat on the throttle body because it was basically rotten. So now I need a new throttle body.
   
2. Bought a new throttle body at a salvage yard and installed it. The whole unit with IAC, TPS, dashpot and all.
   
3. Once installed I drove it about 30 miles. It was idling high and seemed to be slow to idle down after I hit the gas and was causing the tranny to shift.
   
4. I got in the car to go somewhere a couple hours later and the check engine light comes on. Now I am showing codes P1300 and P0120.

I am hoping that this is all due to a bad TPS. Is it possible that a bad TPS would throw a P1300 code?