My silverado is running about 1200 rpm"s, i changed the throttle body sensor, no difference, if i take out the pcv valve, it slows down, but shake it, it is good, the oil cap unscrew it it barley runs, throttle body seems tight? can not find any vacuum leaks? also the break is relly hard, probably high idle? thanks phil

Proper idle speed for this vehicle about 800 RPM; 1200-1400 RPM is indeed too high. This usually occurs due to too much air entering the intake manifold. Air flow during idle is typically controlled by an idle air control (IAC) valve or in newer vehicles (as in this case) an electronic throttle body. The throttle body could be physically binding which could keep the throttle blade open too much. Cleaning the throttle bore and blade is a good first step, but a special function called the "ECM/PCM idle learn procedure" must be performed with an advanced diagnostic scan tool after this repair. Another possible cause for receiving too much air into the intake manifold is a vacuum leak. Vacuum leaks can originate from any area exposed to engine vacuum including the PCV valve, PCV hose, EVAP canister purge valve, throttle body, intake manifold, brake booster hose and brake booster. A diagnostic scan tool capable of viewing live data is a great way to check for vacuum leaks by watching the fuel trim values; if a vacuum leak is present, the computer will be adding extra fuel to maintain the correct air/fuel ratio. Lastly I do want to mention that the idle speed is adjusted higher when the steering wheel is turned or the A/C is turned on. These signals are sent to the ECM from the A/C pressure sensor and power steering pressure (PSP) switch however I've never personally seen either one cause a high-idle concern. You can read more here: https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-ac-high-pressure-hose

check coil and distributor for output

have you checked the coil?

Have the fault code read as it may be a throttle position sensor or idle speed sensor that is at fault.

Hi.

Check the following in order:

IAC valve wiring, connectors and vacuum hoses.
Look for vacuum hoses that are not connected in general.
EGR valve wiring, connectors and vacuum hoses.
PCV system.
Wiring to the two sensors in the air intake.
Check position of the air intake for leaks. Tighten its screws.
Check wiring in general.
Do a code scanning if you have not found anything so far, check wiring of ECM and O2 sensors.

If the car idles up and down there may be an air leak from air intake or IAC, EGR, there may be a vaccuum leak or PCV system may be malfunctioning. Those are the things to check first and with more attention.

Regards.

Ginko

The condition you describe is usually caused be a vacuum leak. You should check all vacuum hoses for tightness.
Maybe PCV valve or things on that system.

Try changing your PCV valve make sure the hose is clean and not full of oil. Also check the elbow end that goes to the intake they tend to collapse from oil saturation. Hope this helps.

One of the sensors or actuators you changed is not electrically compatible with your module. it will look exactly the original but is different. Check for loose cables at the restof the sensor that could be moved when serviced the car

check the PCV hose from the pcv valve to the rear of the intake manifold, real coomon to leak where the line hase a rubber end at manifold.

you should change the tps( throtal position sensor) this can cause that problem