Iat going crazy

Hondata model coverage & ECU application questions.
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dluder
Posts: 61
Joined: Mon Oct 22, 2018 6:08 pm

Iat going crazy

Post by dluder »

Hey guys I've been having issues with my car for a long time but I finally figured why it's jerking like a lean misfire. I did a quick datalog and noticed under temp comp the added iat% was cutting in and out but the iat temp was reading just fine. So to confirm this I added 1% at regular temps and sure enough it's still cutting in and out and failed to deliver a constant 1%. So I disabled iat in hondata and It ran great for a minute and didn't jerk hesitate or anything. Then all of a sudden it started adding 8-10% fuel to iat while it was disabled. I've literally check and replaced everything on this car.
So I replaced iat sensor again today and ohm out wires and both was good. But some wire has to have a break in it. Could I leave iat power red/yellow hooked up to d15 but cut ground green/black I think d22 and run to chasis ground?
This is in 2000 prelude. I've replaced ecu, hondata, all sensors, injectors, some pig tails and wiring. But at least I finally found out what it's doing. Now I just gotta figure out why. A tuner friend said he had a ect go bad one time and it was adding 20% or something crazy. I've gotta figure this out I haven't drove the car in over a year because its drove me crazy trying to figure issue out.
dluder
Posts: 61
Joined: Mon Oct 22, 2018 6:08 pm

Re: Iat going crazy

Post by dluder »

Hey guys I'm hopping to get some ideas or insight on issue. So I believe the iat is pin d22. I'd have to look at harness to confirm this. But where does it get ground from? Thermostat ground? If so I've done replaced thermostat ground and I don't believe I can run iat to chasis ground can I? I ohm tested both iat wires and both tested good. I'm going to go ahead and replace both iat wires unless someone has better idea? I've done replaced conversion harness to rule that out. Lol along with everything else.
dluder
Posts: 61
Joined: Mon Oct 22, 2018 6:08 pm

Re: Iat going crazy

Post by dluder »

Ok so I tried to rewire the iat and learned that it shares a ground with ect. So I'm going to try and run both to chasis. I really hate to do this but I assume my ecu ground is bad and I've replaced the main ground from thermostat to ecu already. Anybody got any ideas.
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Spunkster
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Re: Iat going crazy

Post by Spunkster »

I would not recommend changing the ground locations for this as it may cause a ground loop. If you suspect a damaged wire, then it would be best to replace that wire back to where it should go on the ECU.
dluder
Posts: 61
Joined: Mon Oct 22, 2018 6:08 pm

Re: Iat going crazy

Post by dluder »

Thanks for the reply. I had no luck running both to chasis. It threw a cel for ect and iat. I guess ecu reads ground also. I looked back at datalog and found when I disabled iat the default setting was 1° so that's why it's was adding fuel. Which if it's disabled it shouldn't have been adding any should it? What do you think could be causing this issue?
dluder
Posts: 61
Joined: Mon Oct 22, 2018 6:08 pm

Re: Iat going crazy

Post by dluder »

Spunkster wrote: Mon Mar 01, 2021 12:06 pm I would not recommend changing the ground locations for this as it may cause a ground loop. If you suspect a damaged wire, then it would be best to replace that wire back to where it should go on the ECU.
I changed the wires back and I'm going to look over the logic grounds tomorrow.
dluder
Posts: 61
Joined: Mon Oct 22, 2018 6:08 pm

Re: Iat going crazy

Post by dluder »

Spunkster wrote: Mon Mar 01, 2021 12:06 pm I would not recommend changing the ground locations for this as it may cause a ground loop. If you suspect a damaged wire, then it would be best to replace that wire back to where it should go on the ECU.
I got a crazy idea I'd like to try just trouble shoot. Could I swap pin d11 and d12. They are both sensor grounds. I'd like to try this to see if its a bad ecu ground. Would this hurt anything? Of course I wouldn't leave it like this it would just be a test. I'm out of ideas.
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Spunkster
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Re: Iat going crazy

Post by Spunkster »

You can try it.
dluder
Posts: 61
Joined: Mon Oct 22, 2018 6:08 pm

Re: Iat going crazy

Post by dluder »

So I had no luck trying switch sensor grounds. I also verified all my ecu grounds to thermostat again. I remembered something weird. I use to run crome before hondata. So I tried switching back to crome. But I got a solid cel with 2 different ecu's. So why am I getting solid cel on crome but not on hondata? More importantly what could cause it. Ive done replaced the main relay.
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Spunkster
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Re: Iat going crazy

Post by Spunkster »

I would recommend that you try your ECU on a known working vehicle. IF it works as it should, then you more than likely have a wiring problem in your vehicle.
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