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I was composing my post when the others above me posted.

It seems the P0420 code is inevitable for these cars. When I finally get one, it will likely become another science project like my LAF and EGR sensor investigations.
 

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Discussion Starter #42
I think this will answer most of your questions there:
Scott's Anti-foulers
Thanks. I have a different type of defouler but I put it on there a few minutes ago. I don't have a CEL which seems to be why people use the defoulers but @Willie Williford above recommended putting it on the lower O2 plug so I did. I'm waiting to hear back from him as to what he has to say about what this might accomplish in regard to my issue in post #1.

Well, your sensor looks just like the new-in-box NTK 24301 I have on my desk, down to the numbers and the holes in the end. So I would recommend you NOT replace it. It looks like it is new, and in terrific shape. If you want to test it, you might want to try it in another Insight that is already running well.

Regarding the downstream sensors and catalytic converters...
OK. Super weird...previous owner gutted the cats and put cheap non-indexed plugs in, yet he used the right and expensive O2 sensor. This is good to know though, saves me money.

We will see how it runs with the spacer down low tomorrow and go from there. From what you guys have told me I don't need the O2 sensor nor the lower 2nd cat converter. That pretty much wipes out all my ideas for a fix aside from the indexed plugs. I'll get some of those ordered soon and install and see what happens. Very confused, I've read for hours on the forums and much of the information is contradictory...but I realize there are many variables at play here. I'll sort it out eventually.

Thanks again.
 

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From what you guys have told me I don't need the O2 sensor nor the lower 2nd cat converter. That pretty much wipes out all my ideas for a fix
If the LAF sensor looks as good in real life as in the photos, if it were my car, I would defer replacing it and research other potential causes. But since it's only a visual inspection, if my research and data collected started to point back to it, it might become a point of focus again.

As for the exhaust system, I'd return it to stock.

The questions I have about how it might be impacting the ECU's ability to manage the engine, are eliminated by returning it to stock.

For example, if I start to wonder if a vacuum leak or a manifold air pressure sensor or some other pressure sensor or valve is contributing to the problem, how do I know that what I'm seeing isn't being caused by lower exhaust system back pressure from the gutted cat? The car is set up with that back pressure in place.

Also, be aware that resetting the ECU should not be done blindly. In some cases it can make things worse, at least temporarily, if major problems still exist that the engine was previously compensating for. Here's more info:

  • A reset method - pulling the battery ground - that works on the Insight:
  • This explains a little more about what happens with a reset: [TMO] ECU Reset Mythology
It helps to research the heck out of this stuff online. But keep in mind that there are a bunch of people with good intentions and bad information. For example, much of what is written on the web about the use of oxygen sensors to control fuel trim is written for more rudimentary sensors on cars that don't have lean burn regimens.

So when we see stuff written on the web about how an ECU tries to keep the oxygen sensor centered around 0.6 volts, well, that simply doesn't apply to the Insight. The Insight oxygen sensor actually has much different control system that, unlike the old school sensors which only tell whether the current air fuel ration is either above or below 14.7:1, the Insight setup can tell the ECU what the air/fuel ratio current actually is.

This type of sensor is called a wideband or linear sensor. Some other cars use the same type of sensor, including the CVT, for more precise engine control over varying operating conditions. In fact, you might find helpful information about how wideband sensors work on posts about their use in other cars. The trick is knowing where the similarities stop and the information does not apply to the Insight.

For example, I believe that some Toyotas use linear air/fuel sensors and since there are more of them, articles that are Toyota-centric were easier to find.

But since these cars (and the CVT Insight) never explore the extreme air fuel ratios that the Insight employs, the wideband sensors for these cars are not THAT wideband, and cannot read high ratios as high as the MT Insight operations.

The cheap Ebay sensors are most likely to be the not-as-wideband kind of sensors and may (or may not!) work fine on non-lean-burning cars (like the CVT). But they probably won't work on an MT... unless you happen to get really lucky and happened to buy old Insight MT Denso or NTK stock on Ebay being cleared out, or a sensor from another brand did their homework and is actually repackaging the correct MT sensor from Denso or NTK.

It appears that Bosch attempted include 2002-06 Insights in their catalog by repackaging a Denso part. But it seems that someone didn't know that the Insight MT cars use lean burn and the CVTs don't and there probably was a decision to by Honda to use different sensors to save a buck rather than use the same sensor for both and simply not make use of the extended range of the MT sensor. (It must have been an interesting engineering discussion between Honda, Keihin, Denso and NTK. It would be AWESOME to have a chance to talk to the engineers involved.)

Unfortunately it seems that this difference didn't get passed along (who would have thought that tranmission type matters for a part that has nothing to do with the transmission?) and this restriction failed to get added to the Bosch catalog and this may explain why this sensor appears as compatible with any 2002-2006 Insight on various sites that sell it.
 

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Just found these articles which predate the Insight and discuss the sensors in Honda's earlier lean burn cars which apparently could go up to 22:1 (the Insight goes higher). This is probably one of the more technical informative articles specific to the same type of LAF sensor used in the 2000 and 2001 MT Insights. I imagine Honda must have approached NTK (and Denso) and/or Keihin in discussions on a sensor that could read even higher air fuel ratios when developing for the Insight (or maybe they approached Honda? wish we knew).

Article parts 1 and 2

These probably apply only to the NTK sensor and would need to be adapted to for the Denso.

There is a diagnostic test described in the second article which talks about measuring voltages and simulating lean burn by temporarily unplugging an injector. However, this will only tell you if the sensor is basically functioning. It is unlikely to help with an aged sensor that has simply degraded over time, which will still respond to something like unplugging an injector, but is too contaminated for problem free lean-burn use. It also won't tell you if a sensor is the wrong sensor and can't reach the highest ratios the Insight operates at.
 

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You might want to look at this thread.

Scott
 
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I think this is the original post from “Evox”:

Scott
 
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Interesting.

My grey test bed 325,000 mile car has occasional terrible LB jerkiness O2 sensors/egr etc.

I have new stuff inc NTKO2 enroute from rock auto for a serious upgrade.

If that doesn't fix it I also have a low mileage secondhand throttle/TPS unit to swap in.

I'm usually so busy fettling electronic stuff I neglect engine parts.
 

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Discussion Starter #48
If the LAF sensor looks as good in real life as in the photos, if it were my car, I would defer replacing it and research other potential causes. But since it's only a visual inspection, if my research and data collected started to point back to it, it might become a point of focus again.

As for the exhaust system, I'd return it to stock. The questions I have about how it might be impacting the ECU's ability to manage the engine, are eliminated by returning it to stock.
Thanks again. I installed a defouler on the lower O2 bung and reset the ECU. We'll see how it drives today in a little bit. As for the exhaust, there is more data pointing to the upper O2 sensor being the issue so I'm going to pursue that first. I'm confused as to how that could be the issue since it's (a) the right one and (b) nearly brand new, but such is life with the G1 Honda Insight. See below, before I get a new one I'm looking into the possibility of cleaning it...some say a gasoline soak will do wonders...others say that's a myth.

You might want to look at this thread.

Scott
Thanks a ton. Question, before I splurge for a new O2, since my O2 is supposedly the correct NTK (pics above) and is almost brand new, is there any merit to trying the "soak it in gasoline for a few hours" cleaning method before counting it as defective? I just hate to spend the money when it's almost new, if there is a way to refurbish it I'd like to at least try that first.

I also went ahead and got some B indexed plugs on order just to make that right as well.

The fix by Scott and evox is quoted below for anyone interested:

Problem cured

The OP brought the the car to see a f I could figure out the problem.

I drove the car a great deal with an OBDII C&C hooked up and changed setttings to monitor different things on the car: O2 voltage, tps, EGR, fuel trims, AFR, etc... I could see no odd voltages or signals.

At one point the car finally threw a P0420. I thought this might be the problem. Pulled and inspected the cats, they were not falling apart or crumbling. Reinastalled them with an anti-fouler. Drove car still not fixed.

On 4-9-18 forum member “evox” posted about the same or similar problem, that he had changed an O2 sensor from Bosch back to NTK and his problem was solved.

The next morning I pulled the O2 sensor which was an NTK, I believe original with about 119,000 miles on it. I put in a used know good, not too old NTK sensor and drove the car. The problem was solved, the car ran great. This car never threw a code for an O2 sensor.

Thank you very much to “evox” for posting.

HTH,
Scott
Picked up a 2000 MT a few weeks back, and have been gradually getting it back up to great running condition, and addressing the codes it had. The biggest problem still plaguing it was a jerky lean burn/lack thereof; even after addressing all the main hitters (EGR plate, EGR valve, spark plugs, CAT, O2 Sensors etc.) Today I FINALLY solved the problem with swapping out the supposed direct fit Bosch O2 sensor with the NTK version (I bought the Bosch before doing more extensive research here, rookie mistake).

The car now smoothly goes into lean burn, the way it's supposed to!

I'll post details on the O2 thread later.

Great to see such a great, and informative community so active with these awesome cars.
 

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Before you install the spark plugs I would visually inspect the ignition coils. Chased another problem about a year ago, the ignition coil had a light crack on its boot and it had a slight misfire that wouldn’t trigger a cods.
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Scott
 
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"wouldn't trigger a cods."
Time for coffee!
 

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The problems I’ve described with the O2 sensor and cracked coil boot did not trigger codes, that would have made to diagnosis easy.
I had to drive these cars and chase the problems.

Scott
 

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is there any merit to trying the "soak it in gasoline for a few hours" cleaning method before counting it as defective?
No. They cannot be cleaned and you are more likely to degrade it enough to keep the car from running optimally when everything else is fixed but not enough to tell that cleaning made a difference either way in the car's compromised state. In other words you won't be able to tell if it helped or hurt and you risk degrading or ruining it. Ask me how I know this.

Focus instead on getting a tool like the low cost Bluetooth tool + Torque Pro already discussed. There is no point getting anything more fancy until you start spending money for a pro tool that can read all systems. The Autel MD802 All Systems is a start in that direction because you can read actual sensor values and start to pinpoint where the problem is, and it can live stream data from other ECUs like the IMA that regular code readers cannot do. Though it would be better to get one that can save live stream captures to a PC for analysis. I'm able to do that with my Autel because I wrote a decoder for the files it creates but you want a tool that supports logging out of the box.
 

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Discussion Starter #54
No. They cannot be cleaned and you are more likely to degrade it enough to keep the car from running optimally when everything else is fixed but not enough to tell that cleaning made a difference either way in the car's compromised state. In other words you won't be able to tell if it helped or hurt and you risk degrading or ruining it. Ask me how I know this.
OK thanks. There are a zillion "soak it in gasoline" articles/videos out there followed by a zillion "I did this and my car got 7 more mpg and ran so great" comments on those articles/videos...seeing that the O2 is my next logical choice in parts to throw at this I thought that would be worth a try if I'm going to buy a brand new one anyway to replace it. But I know nothing of gasoline and cleaning O2 sensors and such.

I hear you on the scanner and I'll definitely move in that direction eventually. At this point whether or not it's in lean burn isn't a concern to me, I have read enough that I feel strongly I can tell when it goes in and out of lean burn so knowing that info objectively isn't going to make a difference in this diagnosis. I think.

What is that data?
I've probably read for 5 cumulative hours on this issue now on these forums...over and over (I've quoted several in these 3 pages thus far) people had my exact issue and a new and correct O2 sensor fixed it. I guess that's not really objective data but from reading 10 years of discussion on this I see the O2 sensor come up more than anything else.

An encouraging thing is knowing that many others have encountered this exact issue.

Thank you again to all who are helping me sort this out.
 

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Discussion Starter #55
Ultimately the perfect thing would be to find a forum member who is close who could let me borrow their working O2 sensor, swap it into my car, take a drive, and thus learn whether or not that's the issue. But the nearest member is 2.5 hours away and that means I burn most of a day on an experiment that may or not yield results I'm looking for (assuming they were willing to let me put their part in my car). It sounds like throwing money away but honestly with all that's going on in my life it's easier to just spend the $130 on the new sensor, see what happens, and even if it doesn't work I have a brand new correct and important part installed on my car.
 

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Should a person be concerned about using an anti corrosion spray like BP Blaster before loosen the top, most sensative O2 sensor on a MY 2000? I'm considering buying a spare one but need to remove what's currently working in order to test the new one's compatability. I'm concerned the spray may hurt the sensitivity of the one being removed since it'll need to go back in.
 

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Sorry, not enough time to read all 3 pages but just wanted to let you know i have the EXACT same experience with my 270k mile 2000 MT insight. Lean burning away, but need more acceleration (big enough rolling hills on fwy usually, car warmed up fully). The car then tries to assist, feels like is still in lean burn, but the fcd drops closer to what youd expect out of lean burn. Then the herky jerkies. I can see it coming by assist going first, then fcd dropping, and i usually just quickly lift and reapply gas to trigger a big enough TPS jump to get out of lean burn. Then all good! Its like the car wants to try and stay in lean burn even below 65mpg on fcd on fwy etc.

Note: my o2 sensor is capable of determining correct AFR using obd2 scanners. Can see it clearly transition to 24:1 afr. My obd2 elm327 readers are all no longer functioning so i have no data of this happening. Was planning on just getting obd c&c to observe. Car was always brought to dealership for everything its whole life. So i am sure i at least have a factory O2 sensor and clocked spark plugs. I have not cleaned egr or spark plugs or really done much of anything in 20k miles fwiw
 

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my o2 sensor is capable of determining correct AFR using obd2 scanners. Can see it clearly transition to 24:1 afr.
My near-pro-grade scanner reports air fuel ratio. In my 2004 I suspect that this ratio is a target that the ECU has set and the control loop then makes adjustments to "make it so" by trying to achieve the sensor current reading corresponding to that air fuel ratio.

The data I collected suggests that it hunts for that target current by making adjustments to the fuel injector pulse width.

A separate PID provides actual sensor current readings. In the case of the Bosch sensor whose measurement limit was below what the car was capable of reaching, data logging suggested that the car set a target current reading that would have represented operation at the targeted air fuel ratio. But the sensor data showed that the sensor maxed out at a lower current, and thus never could produce the current the ECU expected. The ECU, trying to reach a higher sensor current, gradually lowered the injector pulse width to increase the air-fuel ratio, seeking the unobtainable current reading. Eventually the ECU gave up and terminated lean burn and set the target to a regular burn mixture. But with the accelerator at a new position from the driver trying to maintain speed through the accrlerator, this resulted in a jolt of acceleration.

I did not see this on several LAF sensors that were the correct part for the car but had many miles of operation on them. Buying a new one gave me light acceleration up shallow inclines at certain speeds and gears without losing lean burn that the worn sensors did not.

This is for a 2004. I cannot describe even the Bosch sensor's behavior as jerky; just a gradual reduction in power followed by a step increase in power when the engine aborted lean burn. Thinking how the LAF control module inside the ECU is different for the 2001- vs 2002+ cars, I don't have enough experience to say whether or not the jerkiness being described (which seems to be described a something repetitive rather than the once per lean burn cycle on my 2004) isn't an inherent behavior of the older LAF system design.

This did not occur every time because the car sets lower air fuel ratio targets the further the RPM is away from the center of lean burn operation, with corresponding current values that are below the senator's limit.
 

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...i have the EXACT same experience with my 270k mile 2000 MT insight. Lean burning away, but need more acceleration (big enough rolling hills on fwy usually, car warmed up fully). The car then tries to assist, feels like it is still in lean burn, but the fcd drops closer to what you'd expect out of [not in] lean burn. Then the herky jerkies.
I'm trying to picture this scenario, if it is indeed the same as OP's, and remember what happens in my car. I have a hard time wrapping my brain around it. In this same scenario, in my car, slight hill approaching, freeway, in lean burn, 5th gear, there's almost 100% of the time no way to invoke assist AND stay in lean burn. I depress the throttle to at least not lose too much speed - and it drops out of lean burn and always assists.*

If the hill (slope, really) is steep enough, which is typically the case, I can't maintain speed, even with max assist (~6kW in 5th). I'd need to downshift to 4th.

So, I'm not sure what 'you guys' are actually expecting to happen. If the hill were too steep, the car would lose speed, engine speed would slow - and there'd be a tendency to lug the engine. You'd need to downshift or really mash the throttle to get max assist. But at freeway speed even max assist doesn't amount to much.

Basically, at freeway speeds there's really no way to have lean burn and assist. And I don't think it pans-out in terms of economy anyway. Even the slightest hill in 5th gear - you'll lose speed, in lean burn or not. I can just barely maintain about 55mph on most freeway hills in 4th gear plus about 20 amps of assist, with FCD at about 50 MPG, range of 45 to at most 60. Pressing the throttle more ends up using more gas, assist doesn't compensate, i.e. more throttle adds more gas than it does electric, so FCD goes down...

I don't get any 'jerkies' during any of this - but I would if I tried to do things the car simply can't do.

* Caveat to this is if you're at high altitude, where 5th gear ICE/IMA interaction will be more like 4th gear at sea level.
 

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Discussion Starter #60
Sorry, not enough time to read all 3 pages but just wanted to let you know i have the EXACT same experience with my 270k mile 2000 MT insight. Lean burning away, but need more acceleration (big enough rolling hills on fwy usually, car warmed up fully). The car then tries to assist, feels like is still in lean burn, but the fcd drops closer to what youd expect out of lean burn. Then the herky jerkies. I can see it coming by assist going first, then fcd dropping, and i usually just quickly lift and reapply gas to trigger a big enough TPS jump to get out of lean burn. Then all good! Its like the car wants to try and stay in lean burn even below 65mpg on fcd on fwy etc.
Good to know someone else is in the same boat and I'm not crazy...mine does exactly this in 3rd 4th and 5th lean burn-ish times.

I'm trying to picture this scenario, if it is indeed the same as OP's, and remember what happens in my car. I have a hard time wrapping my brain around it. In this same scenario, in my car, slight hill approaching, freeway, in lean burn, 5th gear, there's almost 100% of the time no way to invoke assist AND stay in lean burn. I depress the throttle to at least not lose too much speed - and it drops out of lean burn and always assists.*

If the hill (slope, really) is steep enough, which is typically the case, I can't maintain speed, even with max assist (~6kW in 5th). I'd need to downshift to 4th.

I don't get any 'jerkies' during any of this - but I would if I tried to do things the car simply can't do.
I hear what you're saying here but two things...

1, I have driven long enough to know this isn't normal...I understand the way this car is geared and how there is no power ever in 4th or 5th....but what is happening is abnormal...if it were normal it would mean that any time the car was coasting along the driver would need to downshift before accelerating.

2, There is no way Honda built the car this way to perform like this. Something is off.

I'm determined to get a new O2 sensor as I stated above. Have a lot going on in my life right now but in the next little while I'll get one installed and report back.
 
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