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96 LS400 idle rpm and OBD weirdness

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Old 07-14-14, 07:17 PM   #1
lchouinard
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Default 96 LS400 idle rpm and OBD weirdness

Ok 2 things

One I need to know if this is normal. When the car is cold the RPM is higher (~1100rpm) and that I know it's normal, but I shift it in drive the RPM doesn't go down and will have the car "bump" even if I fully apply the brake.

Next, I've plug my ODB tool and I always get a yellow light on the emission led. I loaded torque on my android phone and tried with it and get an get the same problem this guy have with his GS

Click the image to open in full size.

Thing is I don't have any code store in the ECU and drove almost 1000km since I got the car and I believe it should had enough time to calculate the evap info.

I've got my caps for the ECU so that will probably be my next rainy day project. But Idk if those are ECU problem related to what I'm experiencing.
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Old 07-15-14, 12:21 AM   #2
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Sounds like a vacuum leak is there at the canister or at the intake line to me. I don't think it's an ECU issue, but it's a good idea to replace those capacitors for a preventive measure
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Old 07-16-14, 07:43 AM   #3
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Any other ideas, ill look at the vacuum this weekend.

Bad O2 sensors?
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Old 07-19-14, 05:35 PM   #4
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Ok physicaly look at vacuum hoses and looked fine. Didn't had lighter gas to test but here's another bit of info I found playing with Torque

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Shouldn't sensor 2 send out some data?
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Old 07-19-14, 10:59 PM   #5
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Ok, just finished replacing the caps in the ECU

Much more PITA than I expected. First I had to remove the CD changer to get the top bolt, I guess previous gen are different. Also the ground tab on the caps required a lot of heat, my Weller WEDD51 had a hard time getting them hot enough.

Anyway Ill put it back in the car tomorrow and see if it helped, now I too tired and ill start breaking things if I don't stop
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Old 07-21-14, 04:47 AM   #6
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ECU is back in the car and run great as before. Ill try again the OBD reading later today after an hour drive.

As for the idle speed, this is normal behavior apparently. The car run at high RPM(1200-1400) when cold to speed up the heating of the cat. Only thing I found is that it might help to replace the motor mount to lower the jerking when I put it in drive.
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Old 07-21-14, 06:55 PM   #7
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Ok still getting the evap sys incomplete... I guess ill live with it.
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Old 07-22-14, 12:11 AM   #8
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Evaporate system incomplete is because you probably did a hard reset on the system and it hasn't had enough key cycles to finish it's checks. Check again in a week or 2.

You may have an evap problem, but those are usually quick to throw a code, even if it is just for a "evap readiness monitor failure" or a gas cap not being tight enough.
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Old 07-22-14, 05:33 PM   #9
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Yeah Ill give it a few more weeks, CEL never went on and no code store either.
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Old 09-01-14, 09:20 PM   #10
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BAM! After a few more weeks it now says COMPLETE!

Thanks for the help
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Old 09-01-14, 09:20 PM
 
 
 
 
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