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Is there anyway to increase the idle on a 91 Legacy LSi 2.2? The car runs smooth at idle, but the idle sits at 400 rpm when warm. This is too low for the automatic transmission and I have a slippage/delayed engagement of the tranny from a stop. If the car is cold and the idle is still higher, no delayed engagement.

 

Car has 101K

 

Thanks, Todd

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have had 3 91 legacys latly that drop injector pulse on #1 cly at idle ok when reved but at idle low voltage to injector 1 put a noid light on #1 and see if its dim pulse at idle

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Hm interesting I remember some TSB or Endwrench article about no injector pulses on cylinder #1, I thought it said something about it would do that if it thought it could not control the idle. Though I would think they meant because the idle was too high.

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I'll check into that. Although, this engine runs quite smooth at 400. If it was missing a cylinder, I'm not sure it would be so smooth.

 

There is adjustment on the Throttle position sensor, would that change anything?

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You really can't adjust the idle on these cars without it kind of wacking out the ECU. If your TB has a needle valve/screw on top of it like this:

 

http://www.main.experiencetherave.com/subaru/images/TB

 

You can unscrew that, which will allow more air to bypass the throttle plate.

 

You can verify the TPS is adjusted properly with these instructions:

 

http://www.main.experiencetherave.com/subaru_manual_scans/FSM_Scans/TPS_testing3.jpg

 

Short of that....some people adjust the throttle stop, however I would recommend against that as it throws the factory calibration out.

 

Another thing to note is that on the Legacy tachometer, what people think is 500 rpm is actually 750 rpm.

 

The darker hashes are 500 rpm increments, while the lighter hashes are 250 rpm increments. Here's a pic of the tach.

 

http://www.main.experiencetherave.com/subaru/images/combmeter/images/IMG_5845.JPG

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Is it an auto trans? Something I was thinking about today is the autos change the idle depending on whether they're in gear or in park/neutral.

 

On my '96 that switch is really flaky and intermittent, so much so I had to put a pushbutton right to the starter solenoid. Anyway I can tell when I start it if that switch is not making park/neutral because the idle will be really low right from the start, rather than how starting cold usually you're up at 1000 rpm maybe. It causes other slightly strange idling things it seems like too.

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You really can't adjust the idle on these cars without it kind of wacking out the ECU. If your TB has a needle valve/screw on top of it like this:

 

http://www.main.experiencetherave.com/subaru/images/TB

 

You can unscrew that, which will allow more air to bypass the throttle plate.

 

You can verify the TPS is adjusted properly with these instructions:

 

http://www.main.experiencetherave.com/subaru_manual_scans/FSM_Scans/TPS_testing3.jpg

 

Short of that....some people adjust the throttle stop, however I would recommend against that as it throws the factory calibration out.

 

Another thing to note is that on the Legacy tachometer, what people think is 500 rpm is actually 750 rpm.

 

The darker hashes are 500 rpm increments, while the lighter hashes are 250 rpm increments. Here's a pic of the tach.

 

http://www.main.experiencetherave.com/subaru/images/combmeter/images/IMG_5845.JPG

 

I always thought the idle "seemed" low in the dash, even though the car ran fine. Now I know why! Thanks for the info about the tach, didn't even think/realize that was the case!

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My solution is get the tb from a 91 has a bypass valve on it to addjust idle i like thiss tb as the idle is very addjustablle they used it only in 89-91 has a flat head screw in a bore on top of tb

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not easyaly i suck at geting pics on here but if you look directly under the bracket that holds the plastic engine cover the plate thats bolted to the tb with top 2 bolts thiss plate covers the addjustment screw to prevent addjustment you will have to remove it or bend it to axsess screw

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Todd,

 

He's talking about the screw/needle valve I mentioned in my post and in these pictures.

 

http://www.main.experiencetherave.com/subaru/images/TB

 

The 90 MY and some early production 91 MY Legacies were the only ones to get this adjustment screw. So just because your car is a 91 MY, that doesn't mean it will be there.

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That screw on top worked great. I found that you CANNOT use the adjustment screw on the throttle linkage to raise the idle, as the computer compensates and lowers the idle back. Weird!

 

Thanks guys, Todd

Edited by SUBARU3

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Yeah, you should not touch the throttle linkage screw. It's precalibrated to flow a specific amount of air around the throttle. Adjusting that will also throw off the TPS calibration. The TPS can be readjusted using the previous link I posted.

 

Glad you got it all sorted out though.

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