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Old 03-04-2012, 05:53 PM   #1 (permalink)
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VX help/mechanic

I have been fortunate enough to acquire a low mileage 94 VX. It only has a little over 103k and was literally a little old lady's car. It spent it's life on the Oregon coast and does not have the rust in the usual places but there is surface rust other places from the salt air. Anyway, what I really need help with is an idle issue. I've searched and read enough here to know that these are pretty common and that there are many causes so I don't expect anyone to just diagnose it. It looks like the O2 sensor (5 wire) might be pretty new based on the look of it. The car seems to run well if it is wound up a bit but has the bouncing idle and a stutter at lower rpm's and a very light pedal. Exactly the place where you want it to run the best! I guess I am really looking for a trustworthy mechanic or garage not too far from Cincinnati Ohio who can give me an honest diagnosis. I am between Dayton and Cincinnati and a reasonable distance from Columbus if I needed to go there. I can do some repairs myself but don't want to play "hit or miss" since some of these parts can be kind of expensive. I would also be more than happy to meet any experienced members that are not too far away. I'm pretty new to the site and only have a few posts so I don't think I can receive PM's as of yet.

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Old 03-04-2012, 07:02 PM   #2 (permalink)
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It sounds like you have a vacuum leak that is making your idle bounce, most common vacuum leak is the grommet on the breather box, this is a $3 to $4 part and requires someone with small hands to reach it, it's part #3 in the diagram.


Other issue with loss of power at part throttle is the o2 sensor, you can test this by unplugging the o2 sensor and letting it run in open loop, this will hurt your mileage a bit because it's going to run in the default ECU settings, but if the problem goes away then you know it's the o2 sensor for sure and while the o2 sensor should last, I have had one go bad in less then a year and others last 10 years or more.
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Old 03-04-2012, 10:24 PM   #3 (permalink)
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I will certainly try both of those as soon as possible. Those are both very helpful and detailed. Thanks!
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Old 03-05-2012, 08:31 AM   #4 (permalink)
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my insight had similar issues (unstable idle, jerkyness at light throttle around 1500-2000 rpm) and it was from the EGR system being clogged up. So, maybe check that out.
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Old 03-05-2012, 09:38 AM   #5 (permalink)
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I agree it sounds like a vacuum leak.

A good way to quickly track a vacuum leak is to get a can of spray carb cleaner. With the engine running, spray carb cleaner on each part you think might be leaking. Work your way from the head, up the intake manafold, around the throttle body, etc. When the spray finds the leak it will be sucked in and cause a noticable change in engine sound.
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Old 03-05-2012, 11:37 AM   #6 (permalink)
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This thread might be of some help:

http://ecomodder.com/forum/showthrea...ained-967.html

I agree that a vacuum leak is most likely, but I would recommend you unplug the idle air control valve (located on the front of the intake manifold if I'm not mistaken) and see if your problems go away, it might be malfunctioning and it's easier to rule out than a vacuum leak.

Honda Fast Idle Thermo Valves were notorious for causing this kind of thing, but the VX doesn't have one.
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Old 03-05-2012, 01:02 PM   #7 (permalink)
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Thanks everyone. All great info. I did actually read through that thread but the subject was correct, that it was a bit more than I wanted to know. I wasn't sure what all related to the VX. As I've driven this 100 or so miles now I have a few more observations. It seems to be fine when cold and idling fast. Also, I turned the A/C on for a couple of minutes and after shutting it off, the idle was smooth and at the correct rpm. I drove it just a bit after that and the bouncing idle came right back.
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Old 03-05-2012, 07:05 PM   #8 (permalink)
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Unplugged O2 sensor and took a test drive and let it get warmed up. Gentle gas pedal stumble was gone but the bouncing idle still remained. So I guess I have multiple issues. I will go through the other suggestions when I have time to try to figure out what else is going on but I'm assuming that I will have to replace the O2. That was all I had time to check tonight. Thanks again for all of the info. I will post further results when I have them in order to benefit others.
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Old 03-05-2012, 08:12 PM   #9 (permalink)
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I wonder if perhaps you do have a fast idle thermo valve. I've read that the VX does not, but I had that *exact* problem with my engine (from an Integra LS/RS).

The car worked fine cold, but when it warmed up, my fast idle thermo valve didn't close off as it should have and was causing a vacuum leak, and the bouncing was the computer trying to compensate for it. Putting a little bit of load on the engine (such as with air conditioner) seemed to smooth it out. My solution was to take the FITV off and put a small plate in its place.
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Old 03-05-2012, 10:17 PM   #10 (permalink)
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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.


Last edited by Ryland; 03-05-2012 at 10:23 PM..
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