92' VX Runs Good CA ECU but not FED ECU - Fuelly Forums

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Old 07-02-2008, 08:59 PM   #1
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92' VX Runs Good CA ECU but not FED ECU

A little bit of history with the car. Its a 92 CA VX purchased it a month ago, didnt have the right ecu, it had a gsr p72 ecu in there. So I bought a fed A00 ecu, took care of all the CEL, but then the car started to hesitate/stumble around 1.5k-3k.

I then purchased a new l1h1 from ebay, still same results. Today I bought a L00 ecu specifically for the 92 vx cali model. Runs like a champ, so now my question is why is it sluggish on lean burn mode with A00 Ecu and with the Cali model's since lean burn is disabled is vtec-e also disabled? Since lean burn uses vtec-e?
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Old 07-03-2008, 01:54 AM   #2
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i think with the CA L00 ecu, you should be running with the ca o2 sensor that came with the car. With the Fed A00, you should be using the L1H1 sensor.
If it works for you then great!
Gary
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Old 07-03-2008, 04:28 AM   #3
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i think with the CA L00 ecu, you should be running with the ca o2 sensor that came with the car. With the Fed A00, you should be using the L1H1 sensor.
If it works for you then great!
Gary
The fed ECU will not run without the hesitation with the l1h1 sensor, the 92 vx came with the 5 wire l1h1 so I'm running the same sensor for both fed/ca ecu. Unless I'm missing something here...
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Old 07-03-2008, 07:13 AM   #4
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the 92 vx came with the 5 wire l1h1 so I'm running the same sensor for both fed/ca ecu.
Yes, you are. You now own two L1H1s. You had one that came with the car, and then you bought another one. But the old one is probably fine, and you didn't really need the second one. But it's OK that you own a second one, because if you keep your VX for a long time, you will eventually need it. Just keep it wrapped up and stored properly. It can be very easily damaged if exposed to the wrong substances (like vapor/droplets from certain silicone sprays and lubes). Also, as VXs get to be more popular and valuable, you can think of your extra L1H1 as an investment that will grow in value (you could always sell it, in other words).

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why is it sluggish on lean burn mode with A00 Ecu
As I think you realize, the difference between the Fed ECU (A00) and CA ECU (L00) is that the former enables lean burn.

I think what you're experiencing ("sluggish on lean burn mode") is simply the normal feeling of how lean burn works. This is subjective and hard to diagnose via words. But the nature of lean burn is that it can create the feeling of a slight stumble or hesitation. This would typically happen at very low throttle settings, while trying to maintain a steady cruise at low rpm, on level ground. The feeling usually goes away pretty quickly, just by opening the throttle a little more (which essentially turns off lean burn).

If you are using P&G, you will generally not run into this, because P&G means you are almost never using very low throttle settings.

An interesting and paradoxical thing about the Federal VX is that you can drive it two very different ways, and get good mpg both ways:

A) do lots of steady cruising at low throttle, which means lean burn is happening a lot
B) do lots of P&G, which means that lean burn generally doesn't happen

I think B is superior to A (if your goal is to maximize mpg), but I think the difference is not so great, especially as compared with cars that don't have lean burn. I think this might be the key reason that VX owners get great mpg when measured as an absolute number, but not when measured in terms of % over EPA. In cars without lean burn, you can greatly exceed EPA by developing excellent P&G technique. In a car with lean burn, you are already getting great MPG, even if you don't do P&G. Although P&G is still worth something.

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with the Cali model's since lean burn is disabled is vtec-e also disabled? Since lean burn uses vtec-e?
The relationship between lean burn and vtec-e is potentially somewhat confusing.

Lean burn means that when the engine is under a very light load (and that is basically synonymous with saying 'very light throttle'), the ECU sets the mixture to very lean.

vtec-e means that under 2500 rpm, one of the intake valves opens only slightly.

Lean burn is possible because of vtec-e (an ultra-lean mixture would cause engine damage if not for the swirl created by the special valve behavior). But they are separate techniques.

To answer your question, vtec-e is not disabled on the CA model. I'm pretty sure that the only difference between the Federal ECU and the CA ECU is the presence or absence of lean burn.

One more little fact that you probably know, that is worth mentioning. Lean burn requires a Federal ECU and a 5-wire sensor. Those two things are standard equipment on every Federal VX. The CA VX had a 4-wire sensor in '93-'95, but it had the 5-wire sensor in '92. I guess Honda stopped doing that because they figured it was a waste of money. Why did they do it that way to begin with? Maybe they thought it would simplify manufacturing, especially if they thought they might not sell a lot of CA VXs.

Ot maybe they were hoping for a last-minute software breakthrough that would allow them to meet CA standards even with lean burn turned on. Maybe by turning it on in a limited manner.
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Old 07-05-2008, 01:24 AM   #5
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Excellent write up monroe74!!

I do agree with your post however the hesitation that's occurring with the Fed ECU is more than just a slight hesitation, it actually jerks back and forth until you give it some gas to get out of lean burn mode. The lighter the throttle the worse it gets, stumbles and jerks back and forth. All maintenance have been done new oem plug wires, new spark plugs, rotor, cap.
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Old 07-07-2008, 02:31 PM   #6
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Excellent write up monroe74!!
however the hesitation that's occurring .

feels like a exhaust restriction ?
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Old 07-07-2008, 02:41 PM   #7
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however the hesitation that's occurring with the Fed ECU is more than just a slight hesitation, it actually jerks back and forth until you give it some gas to get out of lean burn mode. The lighter the throttle the worse it gets, stumbles and jerks back and forth.
Hmm, that's a bit of a mystery. It sounds like lean burn, except it shouldn't be quite so extreme.

The fact that the problem comes and goes (as you swap the Fed and CA ECU) seems to prove that what's going on is lean burn. But I don't know why it's so extreme. Are you really sure it runs just fine with the CA ECU? No signs of a vacuum leak?

Something you could consider doing is monitoring your lean burn with a DMM. It's easy to do. There are some threads around here on the subject. Let me know if you need help finding them.

This might get you some helpful information, to decide how to handle the situation. Just an idea.

Another idea. Since you already have both ECUs, and you know how to swap them, you could try running a couple of tanks both ways. Depending on your driving style and driving conditions, lean burn might save you a lot of gas, or maybe not so much. This could also help guide you in figuring out how to proceed.
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