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dons2346 01-13-2014 12:10 AM

High Engine RPM on Startup
On startup, the RPM will climb up to 2,000 and then idle back down to around 6oo. It doesn't matter if the engine is hot or cold. Engine is the 4.7 in a '99

Could this be a function of the throttle position sensor and if not, what could cause this? Thanks

Frango100 01-13-2014 09:22 AM

Re: High Engine RPM on Startup
This could have to do with the TPS, but also with the idle air control (IAC) stepper motor. A dirty air passage from the IAC can give idle problems.
Remove the IAC stepper motor and clean the plunjer and air passage very well.
You will have to remove the resonator box for this, because the passage starts at the front of the throttle body. You could run some throttle body cleaner through the air passage with the engine running.
If you have a scanner which shows live data, you could see the TPS sensor % and check if there is any change to the figure while starting.
If you donīt have such scanner, but you do have an Android phone, then you could download the free app "Torque" and just buy a cheap bluetooth dongle and there you go. Besides many live data figures, it will also show you fault codes from the PCM and give you the possibility to errase the PCM fault data. Very handy and cheap scanner (at least if you have the Android phone already).

dons2346 01-14-2014 12:06 AM

Re: High Engine RPM on Startup
Thanks for the info Frank. I do have a Droid phone and tablet so I will get the app.

Now, one more question, where will I find the usb port to plug the dongle into?


Frango100 01-14-2014 01:42 AM

Re: High Engine RPM on Startup
Hi Don. The dongle is not an USB device, but it just fits into the Scanner connector left under the steering wheel. I bought mine directly from China at I think i payed around 20 USD including shipping.
Quite a nice site with a lot of other things as well. You can maybe even buy it locally, don't know about that.
Here the link to the site, eventhough its not the exact same dongle as i have:

dons2346 01-14-2014 11:37 PM

Re: High Engine RPM on Startup
Ok, I got it now. Looked at the site and there are quite a few different dongles to sort through. I did look at the Droid apps and there are a few of those also.

Thanks for your help.


Frango100 01-15-2014 06:07 AM

Re: High Engine RPM on Startup
I see that they now also sell wifi dongles besides the bluetooth, but they are more or less twice the price.
There are indeed several apps available, but " Torque" is at least a very good one.

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