VX will NOT stay in Lean mode...HELP!! - Page 2 - Fuelly Forums

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Old 08-06-2011, 11:18 AM   #11
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Re: VX will NOT stay in Lean mode...HELP!!

I've been meaning to do a write up on this for a while, just haven't gotten to it.
My vx has a similar problem to yours. I had around the same psi as you until I used Seafoam. Now the psi is down because all that carbon was reducing the size of the combustion chamber (that was giving the false positive of a "good" motor). I have plans for a rebuild on my spare motor, when time and money allows.

Anyway.

The vx seems to have two modes. I would characterize them as "flat highway mode" and "mountain climbing mode." 15 years ago, these cars would only ever get into mountain climbing mode when actually climbing a big hill.
Characteristics of mountain mode:
Very difficult to maintain lean burn. Aggressive change between lean and regular. Higher mpgs available in lean burn (as though you were going down a slight hill) but much lower mpgs in enrichment mode.

Characteristics of highway mode:
Much more easy to keep in lean burn, even with small hills. Very much less aggressive change between lean/not lean. Slightly lower mpg's available in lean (I cruise at 72-75mpg on a slight downhill, 69mpg or so on a flat, at 60mph with my mods) but higher mpgs than mountain mode in the non lean mode.

How to get between the two:
I think honda made it so after a long DFCO (just like you were on the down hill side of a mountain) the ecu resets to "highway mode" most of the time. But not all the time. What I do when the car gets into this mountain mode and i don't like it (like when I'm on a flat) is use my kill switch and restart the engine. I make sure to hold the kill switch off for 2 seconds. If not, the car will be back in that mode right away.
Please note that after using the kill switch, it takes about 10-15 secs to make lean burn work again.

So, try killing the motor for 2 seconds, restarting with key or bump start, and see if that changes the characteristics. Note that you may have to give it two or three kills to get to the other mode. You'll get the timing right later.

Hope that helps.
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Old 08-08-2011, 10:05 AM   #12
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Re: VX will NOT stay in Lean mode...HELP!!

Yes, it rolls great! Even hard to stop it rolls so nice.

I will try your method benfrogg. I have shut it down on a hill and the jumped it before the stop and then drove it and it never seemed to change anything. But i try your idea sometime.

The Car may be down here for a couple weeks due to me doing the rust repair and then paint. I will be trying any other ideas that are mechanical while i am doing this. but i may only be able to drive it in-between finishing rust repair and paint.

The things that I am thinking to look into are checking the cat and the rest of the exhaust system, hoping to get a ECU to check that, and testing the V-Tec. It seems to may have oil coming out around it, i am going to test and look into that more.

Once again, thank you for all your ideas and I welcome more, please.
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Old 08-08-2011, 02:52 PM   #13
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Re: VX will NOT stay in Lean mode...HELP!!

^If your solenoid and housing for the V-TEC are leaking, you know that is an easy fix. I fixed that and got the valve cover gasket done, and I consume very little oil over time now.
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Old 08-08-2011, 07:41 PM   #14
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Re: VX will NOT stay in Lean mode...HELP!!

Hey benfrogg, I seen that you had some problems before, that were close to the same problems that I am having and you posted about it. here is the link http://www.gassavers.org/showthread....d+valve+filter

So, what did end up fixing it? Was it just the ground for the O2?

Thankx again
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Old 08-10-2011, 02:11 PM   #15
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Re: VX will NOT stay in Lean mode...HELP!!

VXman-
02 grounding didn't hurt. Did it help? I don't really know. What I've come to realize since owning the mpguino is that there are these two modes. After a DFCO, it takes a few seconds to re-engage the lean burn function. If you have to accelerate after DFCO, it can take much longer to engage. So, the sudden burst of FE with more throttle was lean burn happening, just this time in the "highway" mode as described above.
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Old 08-14-2011, 10:50 PM   #16
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Re: VX will NOT stay in Lean mode...HELP!!

Hey everyone. Interesting thoughts on 2 modes for leanburn benfrogg. Never heard of that, but always sort of wondered if there was more than one 'mode' of lean burn. I often find that I can stay in lean burn more easily after bump starting after doing an EOC.

My $0.02 for the OP. The VX is a more finicky and complex machine than the other civics of that generation. For example, at Autozone you cannot buy the cheaper spark plug wires that are available for all the other civic models of that generation when buying spark plug wires for the VX. Autozone only has the Bosch ones available. So I agree with VXDude. You should get the best OEM spec spark plugs and wires for your VX available. NGK seem to be a popular choice on these forums. Getting those seem like they'd at least rule out one possible variable. I'v never heard of DENSO or of anyone on these forums using them in their VX.
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