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Old 03-08-2012, 09:43 AM   #11 (permalink)
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I am going to try to go about this methodically and save the O2 for last in case some other issue could foul the O2 I want to replace that last. I replaced the grommet #3 in diagram above and things seem to be a little better but not solved. I read some things since then that I want to try soon. I did not reset the ECU after unplugging the O2 and throwing the check engine light. I want to unplug the O2 again after replacing the grommet to see how things are in default mode and then I will reset ECU. I also want to check for vacuum leaks other places. I want to check the EGR system for a clog. I'm not sure I'm ready/willing to follow the procedure of drilling holes in the intake to clean but if I can determine that it needs it, I guess I will. I noticed yesterday before changing the grommet that the idle settled down on it's own (and was maybe even a little low) after it bounced around for maybe 10 seconds. Can someone tell me what #2 is on the diagram above? It appeared to be some kind of valve to me. Is it PCV? Thanks!

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Old 03-08-2012, 05:52 PM   #12 (permalink)
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clean the IACV or get a new one ~$200 or a ebay used ~$40
I have a VX and bouncing idle is a common problem with all civics.
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Old 03-08-2012, 05:55 PM   #13 (permalink)
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the pvc valve is just a tube on the VX, dont even look it it.. except if it is loose.
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Old 03-08-2012, 06:30 PM   #14 (permalink)
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Part #2 in the diagram should be a straight hollow joint, some VX's do have a PCV valve, some do not and the straight joints were sometimes replaced with PCV valves by mechanics who thought something was missing, so it's worth checking to see if either of the joints have a valve in them, if they do then make sure it's moving like it should, if it's gummed up or broken you can replace it or you can carve off the end of the plastic and pull the guts out and leave it as an empty joint.
I've seen after market PCV valves used where the upper elbow is and the after market ones are often two pieces, the valve body being one piece and the 90degree elbow being another, where the two bits of plastic join is also sometimes a vacuum leak point.
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Old 03-11-2012, 07:43 PM   #15 (permalink)
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I think I am making progress. Here is what I've done so far and results.
1. Replaced Grommet for PCV. Did not seem to make much of a difference. Also replaced straight through PCV (looked like original). Still no appreciable change.
2. Cleaned IACV valve. This seems to have improved things (idle not as wild) but they are still not fixed.
3. Unplugged O2 sensor. This cures the stumble at light throttle since it doesn't go into lean burn. Found what I believe to the correct replacement (24300) on oxygensensor.net for $189 so I ordered that.
4. Tested a few lines for vacuum leaks but did not find any.
So now I have some more consistent symptoms but I'm still not exactly sure of the cause. I haven't tried the EGR system as of yet. Now when I drive the car and take it out of gear to coast after being warmed up, the idle slowly fluctuates between about 800 - 1500 rpm if I am above 50 mph. As the car slows the idle fluctuates between about 800-1100 or so. Once I stop the idle will stabilize after about 5-10 seconds and sits right about 1000 rpms. I thought this was a bit high but did not want to adjust it with the O2 unplugged. I'm hoping that the new O2 takes care of the lean burn stumble.
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Old 03-13-2012, 09:05 AM   #16 (permalink)
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Installed new O2 last night and lean burn seems to be working correctly now and the idle issue has also improved. I'm going to drive it this way for a tank or so to see how things are doing.
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Old 03-13-2012, 09:57 AM   #17 (permalink)
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Quote:
Originally Posted by Ryland View Post
Nope, the VX does not have an idle air control valve and there for does not have the idle bounce that comes along when that valve wears out, but what it does have is a little rubber grommet on the crank case breather box that after 15 to 20 years gets dried out so the little plastic fitting that sticks in it no longer fits right, it's a common problem that nearly everyone with a civic vx that I talk to has and it's fixed with a $3 part from the dealer (not sure if the auto part store can get it or not, but the part from the dealer is good for 15 years!!!), it takes 5 minutes to replace, you need a pair of pliers and someone with small hands to reach under the intake manifold to pull out the old one, if you want to be sure that it's really this grommet before investing $3 in parts, you can buy a $2 can of carb cleaner to spray down there but at that point you've made a 2nd trip and after you count gas to go to the store you've doubled your investment in the repair.
You can be sure that it's this grommet if the idle bounce goes away when the engine is at fast idle, such as when it's cold or when the a/c is on (a/c turning on kicks in the fast idle), at fast idle it creates a higher vacuum and the loose fitting part gets sucked in, sealing the gap/vacuum leak.
Thanks Ryland great post. I will try this on mine
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Old 03-13-2012, 01:17 PM   #18 (permalink)
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O2 sensors don't fail near as often as they would like you to believe... Or as often as the OBD system tells you, nearly any intake problem will throw a O2 code... I'd check the grommet...

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Old 03-13-2012, 04:32 PM   #19 (permalink)
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For whatever reason I bought both of my civic vx's with bad o2 sensors, my first one has around 70,000 miles on it's "new" o2 sensor and it's about 5 years old now, my current VX has around 30,000 miles on it's new o2 sensor, going on 3 years, but both cars had their sensor go bad when the car had around 190,000 miles and was around 15 years old.
The "normal" part of the sensor seems to work fine, but the part that picks up on the lean burn seems to be what goes bad after 190,000 miles/15 years, so I'm not sure what is special about that part of these 5 wire sensors but I guess it's also part of why they are a $185 to $300 part instead of a $30 part.
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Old 03-13-2012, 05:13 PM   #20 (permalink)
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My idle floats when I'm rolling and stabilizes when the car comes to a stop. I wasn't sure if this was something the ECU does on purpose, because it's so predictable and consistent - it floats ~800-1500rpm as I roll up to a stop light (clutch in), and when I drop below 5mph it settles down to a nice 850rpm.

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