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Throttle return on '97 Legacy Lsi


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#1 charlierh2

charlierh2

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Posted 30 November 2003 - 11:45 PM

hey,

i have a 1997 Legacy Lsi that has a "sticky throttle". The engine light came on for one day then turned off again but the engine runs at anywhere from 1000rps to about 3000rps in nuetral. I went under the hood and when i played with the throttle manuly it got a little better. My uncle had a Saturn with the same prob and it was a temp sensor. Could it be the same with the Legacy, i also think it could be the throttle cable binding or weak return springs anyone else with this prob. I also know there was a recall on high idle in reverse around 2800rpms could this be connected?
thanx for any help

#2 alias20035

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Posted 01 December 2003 - 12:52 AM

Originally posted by charlierh2
hey,

i have a 1997 Legacy Lsi that has a "sticky throttle". The engine light came on for one day then turned off again but the engine runs at anywhere from 1000rps to about 3000rps in nuetral. I went under the hood and when i played with the throttle manuly it got a little better. My uncle had a Saturn with the same prob and it was a temp sensor. Could it be the same with the Legacy, i also think it could be the throttle cable binding or weak return springs anyone else with this prob. I also know there was a recall on high idle in reverse around 2800rpms could this be connected?
thanx for any help



Go to Autozone (or another autoparts store) and have them connect their ODBII diagnostic device (usually no charge for this). They can download the CEL code stored in the ECU (the code should still be there even though the CEL is now off). Depending on what the code is, it may or may not point you in the right direction. Sometimes the ECU has to guess what the problem is and it guesses wrong, but its usually not hard to figure out where the true problem lies.

Temp sensors are really common on Subaru's. There are two sensors, one for the dash and one for the ECU, it is the ECU one that fails. Its about $40 for a new sensor. If the temp sensor is gone, the ECU will think the engine is cold and run it in cold mode (high idle).

I would rule out problems with the throttle cable first though, problems in this area are not too common, but they are really easy to rule out and correct.

I haven't seen any broken return springs on the throttle body, but I have seen binding accelerator and cruise control cables. I would check that the cable ends are clean, and with another person moving the accelerator pedal check the throttle/cable mechnism out for any signs of binding. You can lubricate the return springs, but generally the cable ends and cables are not lubricated because the lubricant can draw in dust and dirt. Also check the cable case for kinks and damage, sometimes the cables are damaged during repairs (pinched or dropped tool). The accelerator cable may be worn out and in need of a replacement, not too common, but it happens.

You can clean the throttle body and its springs with carb cleaner, sometimes this will free up the throttle mechanism.

Also check out this thread on Idle Air Control (IAC) valves, malfunctioning IAC valves will cause really erratic idle, and in some cases cause the engine to idle at 3,000 or so RPM (if the IAC is stuck open).

http://usmb.ultimate...=&threadid=7944

Another possibility is a failed Throttle Position Sensor (TPS) but this is not very common and the ECU is very good at identifying it, just check that the throttle position sensor is still firmly attached to the throttle body, if it is loose the ECU may get the wrong throttle reading. If loose you will have to tighten it back up in the original position, hopefully you can find the "dirt line" that denotes its original position.




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