Honda Idle Issues, Hunting Idle
After that, I check the operation of the PCV valve by pinching off the supply line to it with a pair of pliers. BTW Honda’s don’t like aftermarket PCV valves, in fact most times you’re better off with a used OE than a new aftermarket part. I’ve actually seen aftermarket PCV valves cause idle problems in some cases, usually a rough idle. The PCV valve is actually a controlled vacuum leak so if it’s not calibrated correctly it can cause idle issues. So if you’re running an aftermarket PCV you might want to exchange it for an OE unit. In my opinion the PCV valves on a Hondas are NOT a maintenance item, they either work or they
don’t from what I’ve seen, so only replace them if you find a problem. I do find problems with Honda PCV valves from time to time. The internals of the valve break apart sometimes and when this happens it causes a vacuum leak, a BIG vacuum leak at that, one that you won’t find by spraying around looking for a vacuum leak using the methods above. Hence the reason pinching off the supply hose fixes the idle issue, you’re really sealing off a vacuum leak when you do this if the PCV valve has come apart internally. If this is what you find replace the PCV valve with an OE unit.
I’ll just say straight out it’s not likely your idle issue has anything to do with the TPS (Throttle Position Sensor). The only time I’ve seen Honda TPS’s go bad is when they were physically damaged, someone tried to adjust it, or if it was an aftermarket unit. So if any of those conditions are true then by all means check the operation of the TPS, if not, leave it alone. One thing I do see from time to time that’s throttle related is someone adjusting the throttle cable too tight, either because they removed the throttle body to clean it or something similar. I’ve seen this condition set a TPS code also. So if you have a TPS code, check the throttle cable first. A quick check for this is to simply try holding the throttle closed at tidle. If the idle calms down when you do this, then it’s likely the throttle is not closing fully which can cause an idle issue for 2 reasons. The first is that it’s unmetered air that the computer has a tough time compensating for, especially at
idle. The second reason is that this may upset the TPS reading which is important as it sends a signal to the computer telling it to go into idle mode. If the computer isn’t told to goto idle because it doesn’t see a closed throttle then idle problems will result as the computer doesn’t know it’s suppose to be controlling functions for an ‘idle’ condition. Hence you get an idle fluctuation or it may not idle at all. Here’s a video that will help with the throttle cable adjustment procedure.
EGR will not effect the idle unless it’s stuck open. Many people go here when they have an idle problem, but to be honest it’s hardly ever the cause of an idle problem on a Honda. When the EGR is a problem it often causes a miss under load, NOT an idle issue. I’m not saying you don’t need to check your EGR ports from time to time as they do clog up, but the EGR is NOT active at idle so it
should not have any effect on the idle unless it’s stuck open as I’ve stated. Even though this post is about Honda idle issues I’ll post the videos I have about cleaning EGR passages on both the 4 cylinder and V6 Honda engines just for good measure. Don’t expect these procedures to improve your idle problem. It may help if you have misfire codes, but it won’t do anything to help your idle situation.
The FITV (Fast Idle Termo Valve) is one of the LAST things to check. The most important part of the procedure is to back it off 1/4 turn after you bottom it out. You won’t find one of these on EVERY Honda engine, mostly on engines older than 1997. The later model engines just use the IAC to control fast idle on a cold start up. This one can often save your butt but if you go too tight you won’t have a good idle when the engine is cold. The adjustment procedure is in this video. Remember not to go here first thing. Check the other items mentioned above first. If you get this adjustment wrong then you won’t have a high idle during cold start up which could be just as bad.