Hanging RPMS and CEL

[Sychotix]

Hey guys, I have had my 420a Talon for about a year now. The hanging rpms used to not be so bad but now I CAN'T stand it anymore, it has gotten worse. It idles between 1100-1200rpms and when I tap the gas it shoots up to 3k and SLOWLY falls back down. My CEL was thrown up one day when I was idling for about a good 10 minutes and it said the IAC valve. Well I changed to a new valve and everything is still the same. It sounds horrible and I can't find anything why it hangs so bad.

 

[jw wrenn]

Does it run a tad hot? The coolant temp sensor can do similar things if its reading incorrect it Could be compensating for a problem you don't have get a multimeter and ohm out your sensors a repair manual should tell what all should read

 

[gofer]

I had this same problem on my N/T, it was the CTS as well. That being said, don't get too crazy and go buy a CTS and go to the trouble of installing it without testing the one you've got first with a multimeter like JW WRENN suggested.

BTW. It's 9-11 ohms @ 77* and 0.6-0.8 ohms @ 212*.

 

[jw wrenn]

Also check your wires leading to the sensors I've had problems there as well

Oh one more check out the screw on your throttle body its on the side close to the valve cover

 

[Sychotix]

Yes it runs a tad hot sometimes but most of the time when I'm idling for about 10 minutes. I'm a beginner in the electrical field so I don't really know how to use a multimeter that well. Where is the CTS and what about the screw to the throttle body? I torqued it like it's supposed to be after I changed the IAC valve and cleaned the throttle body.

 

[Dsmkauai]

Have you tested the tps sensor yet? Looked or cleaned the throttle body, to see if its sticking or not shutting all the way?

 

[Sychotix]

The throttle body is clean. I took about 2-3mm of greased up carbon crap out of it. I replaced the IAC valve and torqued the nuts back on. That's all I have done. I don't know where the TPS or CTS is. Is there anyway someone can post a pic? I'm still learning my beloved 420a.

 

[jayson427]

Get some carb cleaner and spray around the intake areas to look for a vacuum leak. Your car will try to stall if there are any leaks. I bet it's a leak rather then the cts but check it out too. A multimeter is super easy to use.

 

[Sychotix]

Alright well I borrowed my electrical teacher's multimeter for the weekend. So volts or ohms? What electrical thingamuhbobs and I'm checking. Haha

And I'll try the carb cleaner trick again. I couldn't find anything last time.

 

[jayson427]

The cts is underneath the top radiator hose. Take the sensor off and test for ohms, one pin is ground and one pin is power you will figure that part out. Gofer listed the tolerance back up top for the cts on a cold and hot engine.

 

[jw wrenn]

If temp sensor checks good check the wires on its conector also or the connector itself For damage

 

[Sychotix]

Well I have had a guy I knew replace my timing belt, pulleys, and hydraulic tensioner. I terribly needed it. The belt was bad and my tensioner pulley was in pieces. The ball bearings were literally sitting in the bottom of the cover and somehow everything was still running. Once he changed it, the car idled at about 800-900. It sounded better and no more hanging revs. But he has the car again because another code was thrown saying that it has skipped a tooth or loose cam and crank sensors. Hes trying to fix that asap and also my idle/vacuum leak CEL code is still on. (Sorry for the long posts guys...)