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Discussion Starter · #1 ·
So this weekend I went over to my dad's house to work on his 2000 Insight. It's old, it runs, but man it has a serious idle problem.

A video is here:

The symptoms are interesting: Start the car and with no load on the engine it starts and idles. Then as soon as the car starts to charge the IMU battery (a few seconds in) the engine starts to drop RPMs, shudder, then come back up, then down then up. If I turn on the AC it really sags and shudders, and is not happy at all.

What could be the issue? I replaced the ISV with a factory new one 2 years ago to try and fix this, then gave up as I had other things that needed doing. Now I'd like to fix it.

It seems as if the motor doesn't respond to added loads and just goes into the almost stall/catch itself loop. I would like to fix this once and for all.

Car runs fine otherwise. Thanks everyone!
 

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My unconstructive comment is i love 100% of the entire videos commentary. You guys are a hoot!

Constructive comment would be to hold the RPM's at 3500 to charge the hybrid batt for a few minutes or until its done calibrating. If your hybrid is flat and your 12v is flat, then yea its not going to know where to idle. Why is the jump pack still on? Maybe charge the 12v and grid charge the hybrid and try again. If the 12v is dead its going to lose memory of everything. Gotta start with known good first. Dont limp something along with both batteries dead.

edit, whoever disconnect that hose was the hose leading to the fuel pressure regulator.
 

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Discussion Starter · #5 ·
Ok, had a chance to go back to the house and check it out. Here is the status:
1) Pulled the EGR valve and checked the solenoid with a 9v battery across the bottom two contacts: Good news, it opens cleanly and when closed holds a vacuum.
2) Started the car with the EGR off. Interesting, the engine hunts for idle at around 3,000 RPM then drops to 1000 then back up. So having a huge air leak past the throttle seems to make the engine run better.
3) Put the EGR back on, the symptoms are:

  • When car starts it idles well for the first few seconds.
  • When the computer starts charging the traction battery the engine goes to the loping idle where it drops, then recovers with the engine stumbling
  • Once the traction battery is charged the engine idles properly
    • The radiator fan will come on and off once the engine is warmed up, it does not cause idle to change
  • Turning on the AC causes the idle to drop so low it will stall.

  • Removing the line from the fuel enrichment vacuum solenoid causes the idle to increase, enough that it does not bring the engine to near stall while charging the traction battery
It almost feels as if there is too much vacuum in the system, so much so that the engine stumbles under any load. It also feels like there is no throttle "kicker" when loads like the AC come on, they just stall the darn motor.

It's not the EGR valve, that's closed properly and is not admitting air. But it seems like it needs to admit more air at idle.

Anyone near MD who would like to check this out with me? It's pretty baffling, maybe my vacuum sensor is miscalibrated. I might try hooking a vacuum gauge up to it and see what it's doing, are there normal values for vacuum at idle and idle under load?

Thanks!
Chris
 

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I'm not reading terribly closely or thinking about this very hard. But, I'm thinking the idle air control valve (I think on the side of the air box) handles a lot of the control for idle speed... Maybe try unplugging that and see what happens? Inspect it for being plugged, or frayed wires or something?
 

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Discussion Starter · #7 ·
The IAC is new, I installed it in 2020 with a Geniune In-The-Bag-With-Japanese-Air Honda part. However I was reading my own posts from 2000 and spotted something.

One mistake I was making was starting the car from dead battery and idling in the driveway. This is bad: When the battery dies the Insight engine loses all of it's special constants and has to go to a factory mapping until it learns the insanity of the current state (180k+ miles) engine. When I was troubleshooting this taking it out for a 30 minute drive after hooking up the battery was enough to set the constants in variable memory so it could then use that map to idle.

My dad being Dad let my new battery die and killed it beyond dead (it holds no voltage). So we're starting it each time with the default screwed up constants. I'll get it from him, put another brand shiny new battery in, and get rid of whatever parasitic load he put in there that kills the battery in a few months.

sigh Forgot about that. Fortunately the Internet reminds me. Let me see how it works.
 

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Discussion Starter · #8 ·
Well, Dad drove the car over to the house. By the time he got here, the car was idling pretty well with the AC off. Took ownership, pulled the old 12v battery, put in new one, car idled like garbage. Took for 30 mile drive, car idles properly without AC and stumbles down to 500rpm at times with AC on. Doesn't stall though, which is an improvement.

The car forgets the engine tuning settings every time you pull the 12v battery. Then it has to start from a map that was valid 20 years and 170k miles ago. It takes time to re-learn how the engine works.

On to the next problem: Replacing the gas sender.
 

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I know you said you replaced the idle air control valve a couple years ago, but re-reading your earlier posts, it still seems like something in that system could be wrong, plugged, etc. As far as I know, that's the main component/system that adjusts idle speed (maintains idle speed) under slightly differing loads. Plus, it's not the best system even when working right - when my pack charges at idle, my idle is not rock solid, same with cycling AC on and off at idle. It doesn't come close to stalling, but it's quite warble-y for at least a few seconds...

You mentioned that vacuum leaks actually improved idle consistency, that's partially what makes me think it still could be the IAC system. My understanding is that idle speed is primarily controlled simply by varying the amount of air (hence, 'idle air control'). When the load increases, both gas and air need to increase. If the air isn't increasing enough or commensurately, then you'll get the idle problems. If it's not the valve per se, maybe it could be the related passageways in the throttle body??
 

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Discussion Starter · #10 ·
Thanks for the reply! It's not stalling but it does drop the RPMs to about 5 or so bars on the tachometer (around 500rpm) before recovering. Might just need to have the idle air adjust screw adjusted, I did a lot of tinkering before realizing the problem is you have to drive it first after resetting the computer. But it's ok enough for now and I think I will not make any changes to the engine for a few months and let it sort itself out.

Although I do need new grommets for the engine cover, I'll do that next.
 

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^hmm, maybe it was just the need to 'recalibrate'. Sounds like it's better... I've never noticed any difference after pulling neg battery cable - i.e. reversion to 'stock map/data' - vs. after recalibration steps or drive period. I think technically there's a procedure that's supposed to be done, but my read is that the procedure just mimics what's done on a normal drive, like the instructions are meant for a service tech returning the car to an owner. Turn electrical stuff on, bring to operating temperature, turn off.
 

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Discussion Starter · #12 ·
Interesting. I wound up chasing a similar problem on my (now gone) 2001 Prius: The engine was running rough after the 12v battery died including weird HV system codes and I did a swap of the igniter coils. Turns out the car just needed a good 30 minute drive and all was well again.

Might be the mileage: The 2000 has 183,000 miles and the Prius had about 200k miles on it. But I'll drive for a month and see how things balance out. It's nice and hot here in MD, and so far the biggest problem (the overheat) seems to have been fixed with a head gasket, new water pump, and new radiator (the old one literally disintegrated).
 
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