The Symptoms: High-RPM Idle and "Service Engine Soon" Light
My 2002 Chevy S10 displayed a "service engine soon" indicator light on the dashboard. Some panic at this sort of thing, but when a check engine or service engine light is on and not flashing, it's not the end of the world; it simply means something isn't up to specifications or not factory efficient. I hooked up my code reader and it read:
"P0507: Idle Air Control: RPM higher than expected"
Knowing the problem could be the PCV valve or both the PCV and IAC valves, I decided to just replace both. After the job, the vehicle now starts normally and the idle is great at 700-800 RPM. So, for less than $50.00, problem solved.
Tools and Supplies Needed to Remove PCV and IAC Components
This particular truck has a 2002 S10 V6 4.3L engine. Engines may vary across the S10 model types.
Please anticipate one to three hours of labor depending on mechanical skills and know-how. This isn't a particularly difficult job, but it will require basic mechanical skills and you will have to be okay with contact with engine coolant, oil, and grease.
- Idle air control (IAC) valve
- Positive crankcase ventilation (PCV) valve
- Small and large flat head screwdrivers
- Large hose clamp (1 3/4" as displayed)
- #20 torque screwdriver
- Light (to see in small areas)
- Safety glasses
- 5/16" socket, or (as shown) a bit for a drill
- Drill (optional ratchet)
- Magnetic tray for bolts and components
- Nitrile/latex gloves (7 mil or better recommended)
- Engine coolant may be needed if you have a significant coolant loss or to replace was is under requirements. (This S10 requires the common 50/50 green standard coolant)
- Carburetor cleaner (optional rubbing alcohol)
Removing Air Housing and Coolant Hose
The following photos will show step-by-step what to remove to expose both the idle air control and positive crankcase ventilation valves.
In this tutorial, we will replace the IAC first and the PVC last.
WARNING: It is highly recommended to either replace the PCV right away or do it last. Do not leave the PCV valve detached while removing the engine coolant hose. While it would be difficult to get coolant into the small hose, it is possible. So just avoid the risk by doing the PCV as the very first step or the last one.
Step 1: Remove the Throttle Body Air Cover
The throttle body air cover has three connection points: 1) a hand-turned knob to the rear, (2) a screw-clamp, and (3) to the front of the engine it hooks under the front of the throttle body.
- First, remove the knob by turning counter-clockwise until removed
- Second, unscrew (with drill and 5/16" socket) the screw clamp.
- Third, wiggle and pull the housing towards the front of the engine until it unhooks.
- Finally, with the hose in the rear of the housing, you should be able to swing the housing towards the front of the engine to keep it out of the way.
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Caution: Be careful when moving the housing to the front of engine not to stress the plastic tubing, which may crack or break.
Step 2: Remove Mass Air Flow Sensor and Hose
The hose to the mass air sensor must be removed. While it is removed, you should inspect and if necessary clean the housing and hose. This can be done using air and/or rubbing alcohol. Be careful not to damage the sensors inside of the MAF unit.
- Remove the sensor wire clips.
- For safe-keeping, tighten down the screw clamp from the hose to the throttle body housing.
- A wire harness to the underside of the hose (see photo) needs to be released. A small flat-head screwdriver will be useful here.
Also note: if you do take the hose apart from the MAF, be sure to note the direction of the hose and connection points from the MAF to the hose. Please see photo below designating arrow and the rubber tip outside of the screw clamp.
Optional Step: Clean the Throttle Body Valve
My throttle body valve was not terribly carbonized, but it had a noticeable black ring. So, since all this was already apart, why not clean it? Carbon can cause the valve to not fully close and stay open, which in turn causes performance issues, and worse, lower fuel economy. So, do clean the valve as much as possible.
Spray carburetor cleaner or rubbing alcohol into a rag, then clean the valve as much as possible. Don't dump fluid into the throttle body; it is made for air, not fuel or other foreign fluids.
Step 3: Remove the Engine Coolant Hose
While this step may or may not be necessary, it sure makes it much easier to get to the IAC valve that we are working towards replacing. You will need to put a hose clamp in place about 4" to 6" down from the connection point. This will allow removal of the hose with minimal loss of coolant.
After clamping the hose, place some rags at the base of the throttle body unit to catch whatever fluid does escape. If you are not wearing safety glasses, now would be the time to put them on, because when the screw clamp is released and the hose is just beginning to come loose, there is pressure, and coolant will shoot out.
- Clamp hose.
- Loosen the screw clamp.
- Remove the hose. You may need a large flat-head screwdriver to help loosen the hose off the metal connection point.
- Move the hose off to the side, away from the wiring that is soon to be disconnected.
Step 4: Replace the Idle Air Control Valve
This is the whole reason for all the craziness to get here!
- Remove the sensor wires.
- Using a #20 torque screwdriver, remove the screws from the IAC.
- Pull the old IAC out and insert the new one.
- Hand-tighten the screws back into new IAC. Do not over-tighten, but just make it tight.
- Begin in reverse order reassembling all the components, but leave off the throttle body cover for easy access to the PCV valve.
When I compared the old IAC valve to the new one, I saw that the o-ring was very worn and the sensor itself was worn. It was definitely due to be replaced.
Step 5: Remove and Replace the PCV Valve
The next and final component to replace is the PCV valve. This is by far one of the easiest things that can be replaced in this truck and many other vehicles.
- Locate the PCV valve. On the S10, it is between the firewall and the throttle body cover, below of course.
- Pull the valve out, being careful not to snap the hose attached to the valve.
- Rotate the hose to remove the valve.
- Use small flat-head screwdriver if necessary to pry out old valve.
- Replace it with the new valve and push it back into the valve hole.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.